JP2001045001A - Flow control method and communication element to execute the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a flow control in an ATM communication network that can reduce a cell loss in a buffer in a communication element and prevent partiality as to a band utilizing rate between connections from being caused. SOLUTION: The communication element 100 uses a parameter observation section 102, a queue length observation section 103, a congestion decision section 104, an FRTT calculation section 105, a CCR observation section 106 and a time-out observation section 107 to calculate an ACR value that is a maximum input rate at which each connection can input in an ABR service, and uses the queue length observation section 103, the FRTT calculation section 105, an ACR sum threshold calculation section 109 and a congestion occurrence prediction section 112 to decide whether or not any cell abort is caused when an input rate of each connection increases up to the ACR value, and allows an EFCI bit setting section 113 to set a congestion notice signal to an EFCI field of a data cell to decrease the ACR value of the connection.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow control method in a communication network, and more particularly to a flow control method for an ABR (Available Bit Rate) service category connection in an ATM (Asynchronous Transfer Mode) communication network. And a communication element for performing the same.

[0002]

2. Description of the Related Art In recent years, as a service category in an ATM communication network, an ABR which has reliability against cell loss and can effectively use network resources has been attracting attention (for example, "N" of ATM Forum Japan Committee).
ews Letter "1995.9Vol.2 / No.2 No.6 pp.2-3
checking). In this ABR service category, A
Flow control is performed between a plurality of communication elements (for example, an exchange and a multiplexer) constituting a TM communication network and a terminal using the network. This flow control is realized by notifying a terminal of congestion that has occurred in the network and suppressing traffic input to the network by the terminal that has received the notification. Note that the “terminal” here refers to a device that terminates the ABR service.

First, as a method of this flow control, an ATM is used.
Forum Document af-tm-0056.000 `` ATM Forum Traffic
Management Specification Version 4.0 ”EFCI (Explicit Forward Congestion In)
A method for controlling the flow of dication) marking will be described.

[0004] A transmitting terminal that transmits information to a receiving terminal using the ABR service category is required to transmit a resource management cell (hereinafter referred to as an "RM cell") every time a predetermined number of data cells are transmitted. Have been. This RM cell is delivered to the receiving terminal, and the receiving terminal
When an RM cell is received, it is defined that the RM is sent back to the transmitting terminal. The RM cell delivered from the transmitting terminal to the receiving terminal is called a forward RM cell.
The M cell is called a backward RM cell.

[0005] The transmitting terminal sets the value of the EFCI field to "0" when transmitting a data cell, and sets the CI (Congestion Index) when transmitting a forward RM cell.
cation) field value is set to “0”. In addition, the transmitting terminal sets the input permission rate (“ACR (Allowed Cell Rate)
) ") And always transmit cells at a rate less than or equal to the ACR. When the transmitting terminal starts cell transmission, the ACR is set to a value called ICR (Initial Cell Rate).
Each time a cell is received, the value of the ACR is updated according to the following relational expression according to the value of the CI field of the subsequent RM cell. When CI bit = 0 ACR = min {ACR + PCR × RIF, PCR} (101) When CI bit = 1 ACR = max {ACR−ACR × RDF, MCR} (102) where RIF (Rate Increase Factor) ), RDF (Rate
Decrease Factor), PCR (Peak Cell Rate), MCR (M
inimum Cell Rate) is a parameter to be determined when setting up a connection using the ABR service.
These parameters are defined in the R service (hereinafter, these parameters are referred to as “ABR parameters”).
Further, max {A, B} indicates the larger value of the values of A and B, and min {A, B} indicates the smaller value of the values of A and B.

[0006] As described above, the receiving terminal returns the RM cell arriving from the ATM communication network to the transmitting terminal as a backward RM cell. When receiving the data cell from the ATM communication network, the receiving terminal stores the value of the EFCI field of the data cell as the EFCI value. And the rear RM
If the EFCI value is “1” when transmitting the cell to the transmitting terminal, the value of the CI field of the subsequent RM cell is set to “1”.
And then send the backward RM cell, then the EFC
Set the I value to “0”.

[0007] If congestion is detected or expected in the network, the communication element of the network can set the EFCI field of the data cell to "1" (EFCI marking). When congestion is detected in the network and the EFCI field of the data cell is set to "1", the value of the CI field of the backward RM cell is set to "1" when the receiving terminal transmits the backward RM cell to the transmitting terminal. When the transmitting terminal receives the backward RM cell, the value of the ACR of the transmitting terminal decreases according to the above equation (102). As a result, the cell transmission rate to the network is reduced, and congestion is eliminated. Also, when congestion is not detected or expected in the network, the value of the CI field of the backward RM cell is "0" when the transmitting terminal receives the backward RM cell.
01). As a result, the cell transmission speed to the network increases, and the transmission band of the network can be used effectively. Here, the transmission band means the transmission speed of the communication path.

[0008] As an example of such a flow control method of EFCI marking, ATM Forum Document ATM95-1019
`` A Simulation Study of ABR Robustness under Binar
y Switch Modes ”(hereinafter referred to as“ conventional example ”). In this conventional flow control method, when the number of cells in an output buffer of a communication element, that is, a queue length is larger than a predetermined congestion determination threshold, the EFCI bit of a data cell output from an output buffer as a queue is determined. Is set to "1", and when the queue length is smaller than the congestion determination threshold value, the EFCI bit of the data cell output from the queue is set to "0". Hereinafter, the configuration and operation of a communication element that executes the conventional flow control method will be described in detail.

FIG. 20 is a block diagram showing an example of the configuration of an ATM communication network including communication elements for executing the above-described conventional flow control method. This communication network includes terminals 2020, 2
030, 2040 and communication elements 2000, 2010. The communication element 2000 includes a queue 2001,
Parameter observation unit 2002 and congestion threshold value calculation unit 20
03, a congestion determination unit 2004, and an EFCI bit setting unit 2005. Communication element 2010 and communication element 200
0 is connected by a communication path, and terminals 2020,
2030 and 2040 are connected to the communication element 2000 via communication paths. In this example, the terminal 2020,
Information is transferred in the form of a cell from the transmitting terminal accommodated in each of 2030 and 2040 to the receiving terminal in the direction of the communication element 2010 through the communication element 2000. These cells are multiplexed in the queue 2001 of the communication element 2000 and output to the communication element 2010. Although only one configuration for multiplexing is shown in this example, a similar configuration is required for each part where cells are multiplexed and congestion occurs.

Next, the operation of each part of the communication element 2000 will be described. When a cell is input from a communication channel, the queue 2001 stores the cell at the end of the queue. Also, at a predetermined time interval, the first cell among the stored cells is output to the EFCI bit setting unit 2005. The queue 2001 counts the number of cells stored in the queue immediately after a cell is input from a communication path or immediately after a cell is output to the EFCI bit setting unit 2005, and uses the value as a queue length to determine congestion. Output to the section 2004.

The parameter observing section 2002 analyzes the signaling cell when setting up a connection, thereby
It detects the values of parameters such as CR, MCR, RIF, RDF, and FRTT, and outputs the values of those parameters and the connection number of the set connection to the congestion threshold value calculation unit 2003. PCR, MCR, RIF, R
As described above, the DF is set to A when the transmitting terminal receives the backward RM.
A parameter used when updating the CR
T is a parameter indicating the time required from when the transmitting terminal transmits an RM cell to when the same cell is looped back at the receiving terminal and returned to the transmitting terminal again. It is stipulated that the values of these parameters are notified to each communication element using a signaling cell when setting up a connection.

[0012] The congestion threshold value calculation unit 2003 stores a connection number and a parameter value for each connection. Also, when the connection number and the parameter value are input from the parameter observation unit 2002, the congestion threshold value calculation unit 2003 newly stores those values. Then, based on the stored parameter values, the congestion threshold value calculation unit 2003 sets a common one for all connections.
The congestion determination threshold is calculated, and the congestion determination threshold is output to the congestion determination unit 2004.

The congestion judging section 2004 stores a queue length, a congestion judgment threshold value, and a value of a congestion state storage flag. Also, each time a new queue length or congestion determination threshold is input, the congestion determination unit 2004 updates the stored values to a new value, and compares the updated congestion determination threshold and queue length with each other. Compare. Based on the result of the comparison, when the congestion determination threshold is larger than the queue length, the congestion determination unit 2004 sets the congestion state storage bit corresponding to the connection number to “0”, and conversely, If it is larger, the congestion state storage bit is set to "1".

When a data cell is input, EFCI bit setting section 2005 outputs a data cell reception signal to congestion determination section 2004. Upon receiving the data cell reception signal, congestion determination section 2004 outputs the value of the congestion state storage bit to EFCI bit setting section 2005. When the congestion state storage bit is input, the EFCI bit setting unit 2005 sets the EFCI of the data cell when the value is “1”.
When the bit is set to “1” and the value is “0”, the value of the EFCI bit of the data cell is not changed. Then, EFCI bit setting section 2005 outputs the data cell to communication element 2010.

[0015]

The problems in the above conventional example will be described in the following order. First, when multiplexing connections that generate bursty data,
The problem that the cell loss ratio in the switch increases (hereinafter referred to as “problem 1”) will be described. Next, a problem (hereinafter referred to as "problem 2") in which when the above-described conventional flow control method is applied to a communication network to which many communication elements are connected, an unfair bandwidth usage rate occurs between connections. .

<Problem 1> First, the problem that the cell loss ratio in a switch becomes large will be described, taking as an example the case where the conventional flow control method is applied to the communication network shown in FIG. Here, each transmitting terminal shown in FIG. 22 generates data having a large burst as described later.

The communication network shown in FIG.
4, receiving terminals RT1 to RT4, and communication elements Ca and Cb. The communication element Ca and the communication element Cb are connected by a communication path Le. Also, the transmitting terminals ST1 to ST1
ST4 is connected to communication element Ca via communication paths La to Ld, respectively, and receiving terminals RT1 to RT4 are connected to communication element Cb via communication paths Lf to Li, respectively. The transmitting terminals ST1 to ST4 connect to the connections C1 to C1, respectively.
The data cell is transmitted to the receiving terminals RT1 to RT4 via C4. The data cells flowing on the connections C1 to C4 are multiplexed in a queue in the communication element Ca, and then transmitted to the communication path Le. Also, each of the transmitting terminals ST1 to ST1
ST4 generates data at independent times, divides the data into cells, and inputs the cells to the communication network at a rate equal to the ACR. After transmitting all of the data, the transmitting terminals ST1 to ST4 do not transmit cells to the communication network until the next data is generated. Therefore, the input rate from the transmitting terminal to the communication network may suddenly increase from “0” to a large value. Data generated at such a timing that the input rate suddenly increases is referred to herein as "data having a large burst property". Note that the length of each communication path is all 100 km. For the sake of the following discussion, the transmission speed of the communication channel Le is represented by "BW".

FIG. 21 is a diagram showing the connection of each connection C1 to C4 in the buffer in the communication element Ca when the conventional EFCI marking flow control method is applied to the communication network in which cells are multiplexed as shown in FIG. 9 shows an example of a change in the input rate and an example of a change in the queue length in the buffer in the communication element Ca. However, the queue length considered here is the number of cells in the buffer provided at the output port corresponding to the communication path Le of the communication element Ca for multiplexing the cells on the connections C1 to C4 to the communication path Le and transmitting the multiplexed cell. Define. For the sake of simplicity, it is assumed that no buffer other than the above-mentioned buffer exists in the communication element Ca. That is, it is assumed that the communication element Ca is an output buffer type switch having one output port.

First, a change in the input rate of the connection C1 will be described. At time T0, transmission terminal ST
1 generates data. At this time, cell input is started at the ICR rate in accordance with the provisions of the ABR service. Further, in accordance with the provisions of the ABR service, the transmitting terminal ST1 transmits the forward RM cell at a fixed rate. These RM cells, after passing through the communication elements Ca and Cb, respectively,
It is looped back at the receiving terminal RT1 and returned to the transmitting terminal ST1. Here, these RM cells are transmitted from the transmitting terminal ST1.
The time at which the vehicle arrives at is T1. After time T1, every time the transmitting terminal ST1 receives the backward RM cell, the value of the ACR of the connection C1 is calculated according to the equation (10) according to the network congestion state.
1) or changes according to equation (102). And
When the data of the transmitting terminal ST1 is lost, the cell input rate becomes “0”. In this example, from time T1 to time T2
Until the time till, the CI bit of the RM cell becomes “0”
And the input rate is increasing. Further, during the time from time T2 to time T3, the CI bit of the RM cell is "1", and the input rate is decreasing. Also,
It is assumed that the data is lost at time T4 and the data is generated again at time T5. From time T4 to time T
A period during which the transmitting terminal does not perform cell input, such as 5, is defined as an “idle period”.

When data is generated at time T5, transmitting terminal ST1 resumes cell input. The cell input rate at time T5 is equal to the ACR at time T4. Therefore, if the value of ACR at time T4 is large,
At 5, the input rate at the communication element increases sharply, resulting in a rapid increase in queue length. Here, it is assumed that the length of the idle period from time T4 to time T5 is shorter than the timeout period defined by the ABR service.

Thereafter, the input rate of the transmitting terminal ST1 repeats a similar change. Also, transmitting terminals ST2, ST3, S
The change in the input rate of T4 is the same as the change in the input rate of the transmitting terminal ST1.

Next, the change in the queue length will be described.
In the period from time T0 to time T6, since the total value of the cell input rates from all the connections is smaller than the transmission speed BW of the communication channel Le, the cells are not queued in the buffer which is a queue, and the queue length is It is always "0". Next, during the period from time T6 to time T7, the sum of the input rates of all the connections is larger than BW, so that the queue length increases. Then, at time T8
In, since the queue length becomes larger than the congestion determination threshold, the EFCI bit of the data cell output from the queue is set from this time. However, at the time of congestion, there is a delay time until the transmitting terminal responds to the congestion notification information. During this time, every time the transmitting terminal receives the backward RM cell, the input rate increases according to the equation (101). In this example, the time at which the input rate of the connection C1 starts to decrease is defined as time T2. Time T7
From time to time T9, the queue length continues to decrease, and at time T10, the queue length becomes smaller than the congestion determination threshold. Then, the setting of the EFCI bit in the communication element ends. After a lapse of a certain delay time from the time T10, the input rate starts to increase. In this example, the time at which the input rate of the connection C1 starts increasing is defined as time T11. Thereafter, the queue length repeats a similar change.

The delay time described above is the delay time until the data cell containing the congestion notification information reaches the receiving terminal from the communication element, or the time until the RM cell in which the congestion notification information is written arrives at the receiving terminal. Or the time required for the RM cell in which the congestion notification information is written to arrive from the receiving terminal to the transmitting terminal.

Next, cell loss in the switch will be described. As described above, there is a delay time from the start of the congestion notification until the input rate decreases, and therefore, the queue length keeps increasing for a certain time. This increase is larger as the total input rate at that time is larger. In this example, the congestion notification is started at times T8, T13, T14, and T15, and in any case, the queue length continues to increase for a certain time, and the amount of increase in the queue length is the total input rate at that time. The larger is the larger. In particular, at time T16, since the connection C1 generates data and starts inputting by PCR, the total input rate increases and the amount of increase in the queue length increases. As a result, at time T17, the queue length becomes equal to the buffer capacity,
Cell loss occurs.

As described above, when the conventional flow control method is applied to the multiplexing of connections that generate data having a large burst property, the input rate sharply increases at the time of data generation, and as a result, the queue rate increases. The length increases rapidly and the possibility of cell loss increases.

<Problem 2> Next, taking a case where the conventional example is applied to a communication network as shown in FIG. 23 as an example, a description will be given of a problem that unfair bandwidth usage occurs between connections in the conventional example. .

The communication network shown in FIG. 23 includes transmitting terminals SU1 to SU
4, receiving terminals RU1 to RU4, and communication elements Da to Dd
And The communication element Da and the communication element Db are on the communication path Mb, the communication element Db and the communication element Dc are on the communication path Mc,
The communication element Dc and the communication element Dd are connected to each other via a communication path Md. The transmission terminal SU1 is a communication element Da on the communication path Ma, the transmission terminal SU2 is a communication element Da on the communication path Mf, and the transmission terminal SU3 is a communication element Db on the communication path Mh.
The transmitting terminal SU4 is the communication element Dc on the communication path Mj, the receiving terminal RU1 is the communication element Dd on the communication path Me, the receiving terminal RU2 is the communication element Db on the communication path Mg, and the receiving terminal RU3.
Is connected to the communication element Dc via the communication path Mi, and the receiving terminal RU4 is connected to the communication element Dd via the communication path Mk. The transmitting terminals SU1, SU2, SU3, and SU4 are respectively
The data cell is transmitted to the receiving terminals RU1, RU2, RU3, and RU4 via the connections C1, C2, C3, and C4. The data cells flowing on the connections C1 and C2 are multiplexed in the queue of the communication element Da and then both pass through the communication path Mb. The data cells flowing on the connections C1 and C3 are multiplexed in the queue of the communication element Db, and then transmitted together on the communication path Mc. Connection C1, C4
The data cells flowing thereover are multiplexed in the queue of the communication element Dc, and then transmitted together on the communication path Md. Here, it is assumed that the length of each communication path is 100 km. Further, it is assumed that the transmission speeds of all the communication paths are the same, and this transmission speed is represented by "BW".

FIG. 24 shows a change in input rate of each connection in a queue in a communication element when a conventional EFCI marking flow control method is applied to a communication network in which cells are multiplexed as shown in FIG. 5 shows an example and an example of a change in queue length in a multiplex buffer of each communication element. However, in FIG. 24, the queue length of the communication element Da means that the cells on the connections C1 and C2 are
b represents the number of cells in the output buffer of the communication element Da used for multiplexing to b. The queue lengths of other communication elements are defined similarly. The input rate of the connection C2, the input rate of the connection C3, the input rate of the connection C4, and the input rate of the connection C1 are respectively the value in the output buffer of the communication element Da, the value in the output buffer of the communication element Db, and the communication element Dc. In the output buffer of the communication element Da and the value in the output buffer of the communication element Da. Here, for the sake of simplicity, it is assumed that all communication elements are output buffer type switches. In the example, the connection C2 is at time T1, and the connection C3 is at time T2.
At the time T3, the connection C4
Starts cell input at time T0, and after this time, the maximum rate (AC
Assume that a cell is entered at R). Hereinafter, how the input rate and the queue length fluctuate in this example will be described in detail.

First, connection C1, connection C
The change in the input rate and the change in the queue length in the buffer of the communication element Da will be described. here,
The queue length of the buffer of the communication element Da is a cell inside the buffer provided at the output port of the communication element M with respect to the communication path Mb in order to multiplex the data on the connection C1 and the connection C2 to the communication path Mb and transmit the multiplexed data. Represents a number. However, for the sake of simplicity, it is assumed that all communication elements are output buffer type switches having buffers only at output ports.

At time T1, connection C2 is
The cell output is started at the ICR rate according to the ABR service specification. Further, in accordance with the provisions of the ABR service, the transmitting terminal SU2 transmits the forward RM cell at a fixed rate. After passing through the communication element Da and the communication element Db, these RM cells are looped back by the receiving terminal RU2 and returned to the transmitting terminal SU2 as a backward cell. Here, the time when these RM cells (rear RM cells) first arrive at the transmitting terminal SU2 is T4. In this example, during the time from time T4 to time T5, the CI bit of the rear RM cell arriving at the transmission terminal SU2 is “0”, and the transmission terminal SU2 receives the expression ( ACR is increased according to 101).

During this time, the queue length of the communication element Da changes as follows. During the time from time T0 to time T6, the input rate from the connection C2 is smaller than the output rate of the queue, that is, the transmission speed BW of the communication channel, so that the queue length is always “0”. Also, at time T6
After that, the input rate from the connection C2 becomes higher than the output rate from the queue, that is, the transmission speed BW of the communication path, so that the queue length increases. Then, at time T7, since the queue length becomes larger than the congestion determination threshold, the EFCI bit of the data cell output from the queue is set from this time T7. However, at the time of congestion, there is a delay time until the transmitting terminal responds to the congestion notification information. During this time, every time the transmitting terminal receives the backward RM cell, the input rate increases according to the equation (101). Here, the delay time described above is the delay time until the data cell including the congestion notification information arrives at the receiving terminal from the communication element, and the RM cell for transferring the congestion notification information to the transmitting terminal is the receiving terminal. This occurs due to the time until the RM cell in which the congestion notification information is written arrives from the receiving terminal to the transmitting terminal.

Here, after the delay time, the time at which the transmitting terminal SU2 reacts to the congestion notification and the input rate from the transmitting terminal SU2 starts to decrease is defined as time T8, and the queue length becomes the congestion determination threshold value. Time T
9 is defined. Also, a time at which the input rate of the connection C2 becomes smaller than BW and the queue length starts to decrease as a result is defined as time T10.

At time T9, the communication element Da becomes EFC
Finish setting the I bit. When the congestion notification in the communication element Da ends, the input rate of the connection C2 starts increasing at time T11 after a certain delay time has elapsed.

When the input rate of the connection C2 starts to increase, thereafter, the input rate of the connection C2 and the queue length of the communication element Da repeat the same change as described above.

Next, changes in the input rates of the connections C3 and C4 and changes in the queue length in the buffers of the communication elements Db and Dc will be described. Connection C
3 and C4 start inputting cells at times T2 and T3, respectively. Thereafter, the input rates of the connections C3 and C4 and the queue lengths of the communication elements Db and Dc change in the same manner as the input rate of the connection C2 and the queue length of the communication element Da, respectively.

Finally, a change in the input rate of the connection C1 will be described. The connection C1 starts cell input at time T0. However, after time T0, the queue length of any of the communication elements Da, Db, and Dc is always larger than the congestion determination threshold value.
Congestion notification is always performed. Therefore, the connection C1
Is always kept at ICR after time T0. Here, it was assumed that ICR = MCR.

By the way, the total number of cells input to the communication network from each of the connections C1, C2, C3, C4 in the time up to an arbitrary time t is shown in FIG. Is the area surrounded by the curve representing the input rate, the time axis, and the straight line representing time = t. As can be seen from FIG.
Obviously, the number of input cells of the connection C1 is much smaller than the number of cells input from the connections C2, C3, and C4, indicating that there is an unfair average input rate among the connections.

The reason for this is that the congestion notification is also performed in connection C1 even when congestion occurs in any of the communication elements Da to Dd.
This is because congestion notification is more likely to be performed as compared with C2, C3, and C4.

As can be seen from this example, when the conventional example is applied to a communication network in which many communication elements are connected, the congestion of a connection passing through many communication elements is higher than that of a connection passing only a small number of communication elements. The possibility of notification is high, and the average input rate is a low value. For this reason, unfairness occurs in the usage rate of the output band of the communication element between the connections having different numbers of communication elements passing therethrough.

The present invention has been made in order to solve the above problems 1 and 2, and in an ATM communication network, even when multiplexing connections that generate data having a large burst property, a buffer in a communication element is used. An object of the present invention is to provide a flow control method and a communication element for executing the flow control method, which can reduce cell loss and prevent unfairness in bandwidth usage between connections having different numbers of communication elements passing therethrough. .

[0041]

SUMMARY OF THE INVENTION A first aspect of the present invention is an ATM communication network that accommodates one or more connections for transferring information in the form of fixed length cells using an ABR service category. When information is transmitted between a transmitting terminal and a receiving terminal by the ATM communication network, a cell input to the ATM communication network from the transmitting terminal is received, and a predetermined A communication element for transmitting the cell to the receiving terminal after performing the processing, a queue in which cells transmitted in each of the connections are multiplexed and temporarily stored, and a queue for each of the connections. A congestion prediction unit that predicts whether or not congestion occurs in the queue based on an ACR value that is an input permission rate; Congestion notification means for issuing, to the transmitting terminal, an instruction to decrease the ACR held in the transmitting terminal or an instruction to prohibit an increase in the ACR when occurrence of congestion is predicted. It is characterized by.

According to the first aspect, occurrence of congestion is predicted based on the ACR value for each connection,
Since the rate control is performed based on the prediction result, it is possible to reduce the possibility of cell discarding even when the connection rate of a connection that is not currently performing cell input rapidly increases to the ACR value.

According to a second aspect of the present invention, in the first aspect, the congestion predicting means is configured to determine an ACR value for each of the connections based on information included in a cell transmitted on each of the connections and arriving at the queue. ACR calculating means for calculating an ACR value, a total value calculating means for calculating an ACR total value defined as an added value of the ACR values for all of the connections, and a method wherein the ACR total value is determined in advance. And a comparing means for comparing the congestion prediction threshold value calculated by the above-mentioned method. Based on the comparison result by the comparing means, when the ACR total value is larger than the congestion prediction threshold value, congestion occurs in the queue. Then, it is characterized by predicting.

According to the second aspect, the occurrence of congestion is predicted based on the total value of ACR values for each connection, and rate control is performed based on the prediction result. Connection is AC
Even when the input rate is rapidly increased to the value of R, the possibility of cell discarding can be reduced.

[0045] In a third aspect based on the first aspect, the congestion predicting means is arranged so that the congestion notifying means transmits the ACR to the transmitting terminal corresponding to one of the connections.
FRTT calculation means for calculating a rate control delay time, which is a delay time from issuing an instruction to reduce the input rate of cells to the queue until the input rate of cells decreases in response to the instruction, for all of the connections, ACR calculation means for calculating an ACR value which is an ACR value for each of the connections based on information contained in cells transmitted to each of the connections and arriving at the queue, and the ACR value and the rate control delay time Prediction value calculation means for calculating a total maximum input cell number prediction value defined as an addition value obtained by adding the product of all of the connections, and a predetermined method with the total maximum input cell number prediction value Comparing means for comparing the calculated congestion threshold value with the calculated congestion prediction threshold value. , Wherein the total maximum input cell number expected value is predicted that the congestion prediction threshold congestion in the queue is greater than occurs.

According to the third aspect, the maximum value of the number of input cells when all connections input at a rate equal to the ACR is predicted based on the ACR value and the FRTT value for each connection, Since rate control is performed based on the prediction result, the possibility of cell discarding can be reduced even when a connection that is not currently performing cell input rapidly increases the input rate to the ACR value.

The fourth invention is used in an ATM communication network accommodating one or a plurality of connections for transferring information in a fixed-length cell using an ABR service category, and transmitted by the ATM communication network. When information is transmitted between a terminal and a receiving terminal, a cell input to the ATM communication network from the transmitting terminal is received, and a predetermined process is performed on the received cell. A communication element for transmitting the cells, and a queue in which cells transmitted in each of the connections are multiplexed and temporarily stored, and a congestion determination for determining whether or not congestion occurs in the queue. Means and a number of cells from the transmitting terminal corresponding to each of the connections based on the number of cells transmitted on each of the connections and arriving at the queue. Input rate calculating means for calculating an input rate of each of the connections, and for each of the connections, determine whether an input rate of a cell from the transmitting terminal is smaller than an input rate threshold determined by a predetermined method. The input rate determining means to be determined, and when the congestion is determined to occur by the congestion determining means, the connection is determined by the input rate determining means that the input rate of the cell is determined to be smaller than the input rate threshold value A communication element comprising: a congestion notification unit that issues an instruction to reduce the ACR for the connection or an instruction to prohibit an increase in the ACR for the connection to the corresponding transmitting terminal.

According to the fourth aspect of the present invention, when it is determined that congestion occurs, the ACR value is instructed to decrease for the connection determined to have the cell input rate smaller than the input rate threshold. Therefore, the difference between the cell input rate and the value of ACR, which is the input permission rate, becomes small.
As a result, even when connections that generate data having a large burst property are multiplexed, the possibility of cell loss due to a sudden increase in the input rate is reduced.

In a fifth aspect based on the fourth aspect, an ACR value which is an ACR value for each of the connections is calculated based on information contained in a cell transmitted on each of the connections and arriving at the queue. The input rate determining means calculates a value obtained by subtracting a preset constant from the ACR value as the input rate threshold value.

According to the fifth aspect, when it is determined that congestion occurs, the cell input rate is smaller than the cell input rate threshold which is a value obtained by subtracting a preset constant from the ACR value. An instruction to reduce the ACR value is issued for the connection determined to be. As a result, the difference between the cell input rate and the value of the ACR, which is the input permission rate, becomes small, and even when connections that generate data having a large burst property are multiplexed, cell loss due to a rapid increase in the input rate is reduced. The likelihood of occurrence is reduced.

In a sixth aspect based on either the fourth or fifth aspect, the congestion determining means includes a congestion detecting means for detecting congestion in the queue and an ACR which is an input permission rate for each of the connections. And congestion prediction means for predicting whether or not congestion will occur in the queue based on the value of the queue. In this case, the input rate determining means instructs the transmitting terminal corresponding to the connection that the input rate of the cell is determined to be smaller than the input rate threshold to reduce the ACR for the connection or the connection. And issuing an instruction to prohibit an increase in the ACR.

According to the sixth aspect of the present invention, when occurrence of congestion is predicted even when congestion is not detected, the cell input rate is determined to be smaller than the input rate threshold value. An instruction to reduce the value of ACR is issued. As a result, the difference between the cell input rate and the value of the ACR, which is the input permission rate, becomes small. The likelihood of occurrence is reduced.

The seventh invention is used in an ATM communication network accommodating one or a plurality of connections for transferring information in a fixed-length cell using an ABR service category, and transmitted by the ATM communication network. When information is transmitted between a terminal and a receiving terminal, a cell input to the ATM communication network from the transmitting terminal is received, and a predetermined process is performed on the received cell. A communication element for transmitting the cells, and a queue in which cells transmitted in each of the connections are multiplexed and temporarily stored, and a congestion determination for determining whether or not congestion occurs in the queue. Means and an ACR value for each of said connections based on information contained in cells transmitted on each of said connections and arriving at said queue. ACR calculating means for calculating an ACR value, a fair allocation calculating means for calculating a fairly allocated bandwidth value according to a predetermined method based on the output bandwidth of the queue, and comparing the ACR value with the fairly allocated bandwidth value. Comparing means, and when it is determined that the congestion occurs by the congestion determining means, the ACR value based on the comparison result by the comparing means the transmission terminal corresponding to the connection is larger than the fairly allocated bandwidth value Congestion notification means for issuing an instruction to decrease the ACR or an instruction to prohibit an increase in the ACR.

According to the seventh aspect, when it is determined that congestion occurs, congestion notification is performed for a connection having an ACR value larger than the fairly allocated bandwidth value. Also in a network, congestion notifications do not concentrate on connections passing through many communication elements. As a result, the unfairness between the connections regarding the usage rate of the transmission band is reduced.

In an eighth aspect based on the seventh aspect, the fair allocation calculating means obtains the number of active connections, which is the number of connections for inputting cells to the queue, and calculates all active connections using the ABR service. The fairly allocated bandwidth is calculated by dividing the ABR service transmission rate, which is the rate at which all cells of the connection are output from the queue, by the number of active connections.

In a ninth aspect based on the seventh aspect, the fair allocation calculation means obtains the number of ABR connections which is the number of connections using the ABR service among the connections set on the queue. A
The fairly allocated bandwidth value is calculated by dividing the ABR service transmission rate, which is the rate at which all cells of all connections using the BR service are output from the queue, by the number of ABR connections.

A tenth invention is used in an ATM communication network accommodating one or a plurality of connections for transferring information in the form of fixed-length cells using the ABR service category, and transmitted by the ATM communication network. When information is transmitted between a terminal and a receiving terminal, the ATM is transmitted from the transmitting terminal to the ATM.
A communication element for receiving a cell input to a communication network, performing a predetermined process on the received cell, and then transmitting the cell to the receiving terminal, wherein the cell is transmitted through each of the connections. Are multiplexed and temporarily stored, and a congestion determining means for determining whether or not congestion occurs in the queue, based on the number of cells transmitted to each of the connections and arriving at the queue. Input rate calculating means for calculating a cell input rate from the transmitting terminal corresponding to each of the connections, and fair allocation calculating means for calculating a fairly allocated bandwidth value by a predetermined method based on an output bandwidth of the queue. And the cell input rate from the transmitting terminal corresponding to each of the connections is equal to the fairly allocated bandwidth value. Input rate determining means for determining whether or not the cell input rate is greater than the fairly allocated bandwidth based on the determination result by the input rate determining means when the congestion determining means determines that the congestion occurs. Congestion notification means for issuing an instruction to decrease the ACR, which is an input permission rate for a connection larger than the value, or an instruction to prohibit an increase in the ACR for the connection to the transmitting terminal corresponding to the connection. It is characterized by.

According to the tenth aspect, when it is determined that congestion occurs, congestion notification is performed for a connection having a cell input rate greater than the fairly allocated bandwidth value. Even in a network, congestion notifications do not concentrate on connections passing through many communication elements. As a result, the unfairness between the connections regarding the usage rate of the transmission band is reduced.

According to an eleventh aspect, in the tenth aspect,
The fair allocation calculation means obtains the number of active connections, which is the number of connections that input cells to the queue, and indicates the rate at which all cells of all connections using the ABR service are output from the queue. The fairly allocated bandwidth value is calculated by dividing an ABR service transmission rate by the number of active connections.

According to a twelfth aspect, in the tenth aspect,
The fair allocation calculation means obtains the number of ABR connections which is the number of connections using the ABR service among the connections set on the queue, and all cells of all the connections using the ABR service are in the queue. The fairly allocated bandwidth value is calculated by dividing the ABR service transmission rate, which is the rate output from the ABR connection, by the number of ABR connections.

A thirteenth invention is used in an ATM communication network accommodating one or more connections for transferring information in the form of fixed-length cells using the ABR service category, and transmitted by the ATM communication network. When information is transmitted between a terminal and a receiving terminal, the ATM is transmitted from the transmitting terminal to the ATM.
A communication element for receiving a cell input to a communication network, performing a predetermined process on the received cell, and transmitting the cell toward the receiving terminal, wherein the cell is transmitted through each of the connections. Are temporarily multiplexed and temporarily stored, congestion determining means for determining whether or not congestion occurs in the queue, and information included in a cell transmitted to each of the connections and arriving at the queue. ACR calculation means for calculating an ACR value that is an ACR value for each of the connections based on
ACR for finding the maximum ACR value that is the maximum value of the R values
Maximum value calculation means; ACR comparison means for comparing the ACR value for each of the connections with an ACR threshold defined as a value obtained by subtracting a predetermined constant value from the ACR maximum value; When the determination means determines that the congestion occurs, the ACR
A congestion notification that issues an instruction to decrease the ACR or an instruction to prohibit an increase in the ACR to the transmitting terminal corresponding to the connection in which the ACR value is larger than the ACR threshold, based on a comparison result by the comparing means. Means.

According to the thirteenth aspect, when it is determined that congestion occurs, a connection having an ACR value larger than an ACR threshold value which is a value obtained by subtracting a predetermined constant value from the ACR maximum value is applied to a connection. A congestion notification is performed. As a result, the congestion notification can be performed only for the connection whose ACR value is close to the ACR maximum value. Therefore, even in a communication network in which many communication elements are connected, the congestion notification is performed for the connection passing through many communication elements. Don't concentrate. As a result, the unfairness between the connections regarding the usage rate of the transmission band is reduced.

A fourteenth invention is used in an ATM communication network accommodating one or a plurality of connections for transferring information in the form of fixed-length cells using the ABR service category, and transmitted by the ATM communication network. When information is transmitted between a terminal and a receiving terminal, the ATM is transmitted from the transmitting terminal to the ATM.
A communication element for receiving a cell input to a communication network, performing a predetermined process on the received cell, and transmitting the cell toward the receiving terminal, wherein the cell is transmitted through each of the connections. Are multiplexed and temporarily stored, a queue, and congestion determining means for determining whether or not congestion occurs in the queue, based on the number of cells transmitted to each of the connections and arriving at the queue. An input rate calculating means for calculating a cell input rate from the transmitting terminal corresponding to each of the connections; and an input rate maximum for obtaining an input rate maximum value which is a maximum value of the cell input rates for each of the connections. Value calculation means, the cell input rate for each of the connections, and the input rate maximum value Input rate comparing means for comparing an input rate threshold defined as a value reduced by a predetermined constant value, and when the congestion determining means determines that the congestion occurs, the input rate comparing means An instruction to decrease the ACR, which is an input permission rate for a connection in which the cell input rate value is greater than the input rate threshold, or an instruction to prohibit an increase in the ACR for the connection based on the comparison result according to the connection. And a congestion notification means for issuing to the transmitting terminal.

According to the fourteenth aspect, when it is determined that congestion occurs, a connection having a cell input rate higher than an input rate threshold value which is a value obtained by subtracting a predetermined constant value from an input rate maximum value. Is notified. As a result, the congestion notification can be performed only for the connection whose cell input rate is close to the maximum value of the input rate. Therefore, even in a communication network in which many communication elements are connected, congestion is not applied to the connection passing through many communication elements. Notifications do not concentrate. As a result, the unfairness between the connections regarding the usage rate of the transmission band is reduced.

A fifteenth invention is an ATM which accommodates one or more ABR service connections for transferring information in the form of fixed-length cells using ABR service categories.
Used in a communication network, when information is transmitted between a transmitting terminal and a receiving terminal by the ATM communication network, receiving a cell input to the ATM communication network from the transmitting terminal; A communication element for transmitting the cell to the receiving terminal after performing a predetermined process, and a queue in which cells transmitted in each of the ABR service connections are multiplexed and temporarily stored, A congestion determining means for determining whether or not congestion occurs in the queue; and an ACR for each of the ABR service connections, based on information contained in cells transmitted to each of the ABR service connections and arriving at the queue. ACR to calculate value Vacr
A calculating means, and a level threshold T which is an n constant set in advance so as to satisfy a relationship of T (i1) <T (i2) with respect to integers i1 and i2 satisfying i1 <i2.
Based on (0), T (1),..., T (n−1), 0 ≦ i
For an integer i of ≦ n−1, the ACR value of the connection of the ABR service connection in which the ACR value Vacr is larger than the level threshold value T (i) becomes the level threshold value T (i). Virtual ACR total value calculating means for calculating the total value of the ACR values of the ABR service connection assuming that they are equal as a virtual ACR total value TACR (i), and TACR for a predetermined input rate target value Tg_Rin If (0)> Tg_Rin, select all the ABR service connections, and TACR (j)> Tg_Rin ≧ TACR (j−1)
If there exists an integer j satisfying 1 ≦ j ≦ n−1, a level threshold T () corresponding to an integer smaller by 1 than the integer j satisfying TACR (j)> Tg_Rin ≧ TACR (j−1) A connection having the ACR value Vacr greater than j-1) is selected from the ABR service connections, and an integer j satisfying TACR (j)> Tg_Rin
If there is no congestion, the connection selection means for selecting from among the ABR service connections a connection in which the ACR value Vacr is greater than the level threshold value T (n-1), and the congestion determination means generates the congestion. When it is determined that the connection is selected by the connection selecting unit, the transmitting terminal issues an instruction to decrease the ACR for the selected connection or an instruction to prohibit an increase in the ACR for the connection. And congestion notification means.

According to the fifteenth aspect, when it is determined that congestion occurs, the virtual ACR total value TACR
An instruction to decrease the ACR is issued as a congestion notification to the connection selected based on the comparison between (i) and the input rate target value Tg_Rin. Here, the connections for which the congestion notification is performed are selected such that the total value of the ACR of each connection becomes close to the input rate target value Tg_Rin when the congestion notification is performed for those connections. Therefore, even in a communication network to which many communication elements are connected, congestion notification is not concentrated on connections passing through many communication elements, so that unfairness in connection of transmission band usage between connections is reduced. further,
At the time of the congestion notification, the sum of the ACRs is equal to the input rate target value Tg.
_Rin quickly converges, so the input rate target value Tg_Rin
Is set to a value close to the transmission speed of the queue, the possibility of buffer overflow in the queue can be reduced.
In addition, since the ACR total value quickly converges to the input rate target value Tg_Rin, the input rate does not decrease to an extremely small value due to excessive congestion notification, so that the transmission band can be effectively used.

According to a sixteenth aspect, in the fifteenth aspect,
The virtual ACR total value calculating means calculates 0 ≦ i based on the level thresholds T (0), T (1),..., T (n−1).
A variable C (i) defined for an integer i satisfying ≤n, and defined as the number of connections satisfying the relationship Vacr≤T (0) among the ABR service connections when i = 0, A when 1 ≦ i ≦ n−1
T (i-1) <Vac among BR service connections
Defined as the number of connections satisfying the relationship r ≦ T (i), and defined as the number of connections that satisfy the relationship Vacr> T (n−1) among the ABR service connections when i = n. A first calculating means for calculating a variable C (i), and a total number of levels N (j) defined for an integer j such that 0 ≦ j ≦ n,
Level total number N defined as an addition value obtained by adding (i) to all integers i satisfying j ≦ i ≦ n
A second calculating means for calculating (j), and a threshold calculation parameter CT defined for an integer j such that 0 ≦ j ≦ n−1
h (j), and when i = 0, T (0) × N (0)
When 1 ≦ i ≦ n−1, ΔT (i) −T
(I-1) a threshold calculation parameter C defined as an addition value obtained by adding the value V (i) calculated by｝ × N (i) to all integers i satisfying 0 ≦ i ≦ j
Third calculating means for calculating Th (j) as the virtual ACR total value TACR (j), wherein the connection selecting means is configured to define the integer j defined as 0 ≦ j ≦ n−1. An ACR threshold value defined based on the threshold value calculation parameter CTh (j), wherein CTh (0)> Tg_Rin with respect to a preset input rate target value Tg_Rin.
Is defined as “0”, and CTh (j)>
When there is an integer j satisfying 1 ≦ j ≦ n−1 that satisfies Tg_Rin, a level threshold T (jt−j) corresponding to an integer smaller by 1 than the minimum value jt of the integer j satisfying CTh (j)> Tg_Rin. 1) and CTh (j)> Tg
T (n-1) if there is no integer j satisfying _Rin
ACR threshold value calculating means for calculating an ACR threshold value defined as: and ACR comparing means for comparing the ACR value Vacr and the ACR threshold value for each of the ABR service connections;
Based on the comparison result by the R comparing means, the value of the ACR V
acr is selected from the ABR service connections from among the ABR service connections, and the congestion notification means selects the connection by the connection selection means when the congestion determination means determines that the congestion occurs. To the transmitting terminal corresponding to the selected connection, the AC for the selected connection
Congestion notification means for issuing an instruction to decrease R or an instruction to prohibit an increase in the ACR for the connection.

A seventeenth invention is directed to an ATM which accommodates one or a plurality of ABR service connections for transferring information in the form of fixed-length cells using an ABR service category.
Used in a communication network, when information is transmitted between a transmitting terminal and a receiving terminal by the ATM communication network, receiving a cell input to the ATM communication network from the transmitting terminal; A communication element for transmitting the cell to the receiving terminal after performing a predetermined process, and a queue in which cells transmitted in each of the ABR service connections are multiplexed and temporarily stored, Congestion determination means for determining whether or not congestion occurs in the queue; and, based on the number of cells transmitted to each of the ABR service connections and arriving at the queue, from the transmitting terminal corresponding to each of the connections. Input rate calculation means for calculating the input rate Rcin of the cell of i, and integers i1 and i2 satisfying i1 <i2
, A threshold value T, which is an n constant set in advance to satisfy the relationship of T (i1) <T (i2).
Based on (0), T (1),..., T (n−1), 0 ≦ i
For an integer i ≦ n−1, the input rate of the cell for the connection of the ABR service connection in which the input rate Rcin is greater than the level threshold T (i) is equal to the level threshold T (i). The sum of the input rates of the cells for the ABR service connection, assuming that they are equal, is the virtual input rate total value TRc
a virtual input rate total value calculating means for calculating as in (i), and the aforementioned A when TRcin (0)> Tg_Rin with respect to a preset input rate target value Tg_Rin.
Select all BR service connections, TRcin
(J)> Tg_Rin ≧ TRcin (j−1) 1 ≦
TRcin when there is an integer j satisfying j ≦ n-1
(J)> Tg_Rin ≧ TRcin (j−1) A level threshold value T corresponding to an integer smaller than 1 by an integer j that satisfies TRcin (j−1).
A connection having the input rate Rcin higher than (j-1) is selected from the ABR service connections, and if there is no integer j satisfying TRcin (j)> Tg_Rin, the level threshold T (n-1) ), The connection having the input rate Rcin higher than that of the AB
Connection selection means for selecting from among R service connections, and when the congestion determination means determines that the congestion occurs, the transmission terminal corresponding to the connection selected by the connection selection means is selected. Congestion notification means for issuing an instruction to decrease the ACR which is an input permission rate for the connection or an instruction to prohibit an increase in the ACR for the connection.

According to the seventeenth aspect, when it is determined that congestion occurs, the virtual input rate total value TRci
n (i) and the input rate target value Tg_Rin, the connection selected based on the ACR
Is issued. Here, the connections for which the congestion notification is performed are selected such that the total value of the cell input rates of the respective connections becomes close to the input rate target value Tg_Rin when the congestion notification is performed for those connections. Therefore, even in a communication network to which many communication elements are connected, congestion notification is not concentrated on connections passing through many communication elements, so that unfairness in connection of transmission band usage between connections is reduced. Furthermore, at the time of the congestion notification, the sum of the input rates quickly converges to the input rate target value Tg_Rin. Therefore, if the input rate target value Tg_Rin is set to a value close to the transmission speed of the queue, there is a possibility that the buffer overflows in the queue. Can be smaller. In addition, since the input rate total value quickly converges to the input rate target value Tg_Rin, the input rate does not decrease to an extremely small value due to excessive congestion notification, so that the transmission band can be effectively used.

According to an eighteenth aspect, in the seventeenth aspect,
The virtual input total value calculating means may calculate the level threshold T
0 ≦ i ≦ based on (0), T (1),..., T (n−1)
a variable C (i) defined for an integer i of n, defined as the number of connections that satisfy the relationship of Rcin ≦ T (0) among the ABR service connections when i = 0, A when ≤i≤n-1
T (i-1) <Rci of BR service connections
Defined as the number of connections satisfying the relationship n ≦ T (i), and defined as the number of connections satisfying the relationship Rcin> T (n−1) among the ABR service connections when i = n. A first calculating means for calculating a variable C (i), and a total number of levels N (j) defined for an integer j such that 0 ≦ j ≦ n,
Level total number N defined as an addition value obtained by adding (i) to all integers i satisfying j ≦ i ≦ n
A second calculating means for calculating (j), and a threshold calculation parameter CT defined for an integer j such that 0 ≦ j ≦ n−1
h (j), and when i = 0, T (0) × N (0)
When 1 ≦ i ≦ n−1, ΔT (i) −T
(I-1) a threshold calculation parameter C defined as an addition value obtained by adding the value V (i) calculated by｝ × N (i) to all integers i satisfying 0 ≦ i ≦ j
Th (j) is calculated as the virtual input rate total value TRcin.
(J) calculating the threshold value calculation parameter CTh (j) defined for an integer j satisfying 0 ≦ j ≦ n−1.
Is an input rate threshold value defined on the basis of CTh with respect to a preset input rate target value Tg_Rin.
If (0)> Tg_Rin, it is defined as “0”, and if there is an integer j satisfying 1 ≦ j ≦ n−1 that satisfies CTh (j)> Tg_Rin, an integer satisfying CTh (j)> Tg_Rin defined as a level threshold T (jt-1) corresponding to an integer one less than the minimum jt of j,
Input rate threshold value calculating means for calculating an input rate threshold value defined as T (n-1) when there is no integer j satisfying CTh (j)>Tg_Rin;
Input rate comparing means for comparing the input rate Rcin and the input rate threshold value for each of the R service connections, and based on a comparison result by the input rate comparing means, the input rate Rcin is set to the input rate threshold. A connection larger than the value
BR service connection, the congestion notifying unit, when the congestion determining unit determines that the congestion occurs, the transmission terminal corresponding to the connection selected by the connection selecting unit, the selection Instruction to reduce the ACR for the connection or the ACR for the connection
Congestion notification means for issuing an instruction to prohibit the increase in

According to a nineteenth aspect, information is transmitted between a transmitting terminal and a receiving terminal by an ATM communication network accommodating one or a plurality of connections for transferring information in a fixed-length cell using an ABR service category. When transmitted, the A
A flow control method performed between a communication element included in a TM communication network and said transmitting terminal and said receiving terminal, wherein cells transmitted in each of said connections are multiplexed and temporarily stored. Whether or not congestion occurs in the queue, a congestion prediction step to predict based on the value of the ACR which is an input permission rate for each of the connections, and when the occurrence of the congestion is predicted in the congestion prediction step, A congestion notification step of issuing from the communication element including the queue to the transmitting terminal an instruction to decrease the ACR held in the transmitting terminal or an instruction to prohibit an increase in the ACR. And

A twentieth aspect of the present invention relates to a method for transmitting information between a transmitting terminal and a receiving terminal through an ATM communication network accommodating one or a plurality of connections for transferring information in a fixed-length cell using an ABR service category. When transmitted, the A
A method of flow control performed between a communication element included in a TM communication network and said transmitting terminal and said receiving terminal, wherein cells transmitted in each of said connections are multiplexed and temporarily stored. A congestion determining step of determining whether or not congestion occurs in a queue; and a cell input from the transmitting terminal corresponding to each of the connections based on the number of cells transmitted in each of the connections and arriving at the queue. An input rate calculating step of calculating a rate, and for each of the connections, determining whether the cell input rate from the transmitting terminal is smaller than an input rate threshold determined by a predetermined method. Input rate determination step, and when it is determined that the congestion occurs in the congestion determination step, In the input rate determination step, the transmitting terminal corresponding to the connection whose cell input rate is determined to be smaller than the input rate threshold value is instructed to decrease the ACR for the connection or increase the ACR for the connection. A congestion notification step of issuing a prohibition instruction.

According to a twenty-first aspect, information is transmitted between a transmitting terminal and a receiving terminal by an ATM communication network accommodating one or a plurality of connections for transferring information in the form of fixed-length cells using an ABR service category. When transmitted, the A
A flow control method performed between a communication element included in a TM communication network and said transmitting terminal and said receiving terminal, wherein cells transmitted in each of said connections are multiplexed and temporarily stored. A congestion determining step of determining whether or not congestion occurs in the queue; and an ACR value which is an ACR value for each of the connections based on information contained in cells transmitted to each of the connections and arriving at the queue. AC to calculate
An R calculation step, a fair allocation calculation step of calculating a fairly allocated bandwidth value by a predetermined method based on the output bandwidth of the queue, a comparing step of comparing the ACR value with the fairly allocated bandwidth value, When it is determined in the congestion determination step that the congestion occurs, the ACR is reduced for the transmitting terminal corresponding to the connection in which the ACR value is larger than the fairly allocated bandwidth value based on the comparison result in the comparison step. A congestion notification step of issuing an instruction or an instruction to prohibit an increase in the ACR.

According to a twenty-second invention, information is transmitted between a transmitting terminal and a receiving terminal by an ATM communication network accommodating one or a plurality of connections for transferring information in a fixed-length cell using an ABR service category. When transmitted, the A
A flow control method performed between a communication element included in a TM communication network and said transmitting terminal and said receiving terminal, wherein cells transmitted in each of said connections are multiplexed and temporarily stored. A congestion determining step of determining whether or not congestion occurs in a queue; and a cell input from the transmitting terminal corresponding to each of the connections based on the number of cells transmitted in each of the connections and arriving at the queue. An input rate calculating step of calculating a rate, a fair allocation calculating step of calculating a fairly allocated bandwidth value by a predetermined method based on an output bandwidth of the queue, and the fair allocation calculating step of calculating a fairly allocated bandwidth value from the transmitting terminal corresponding to each of the connections. An input rate determination for determining whether a cell input rate is greater than the fairly allocated bandwidth value. A step, when the congestion is determined to occur in said congestion determining step,
Based on the determination result in the input rate determination step, the cell input rate is an input permission rate A for a connection larger than the fairly allocated bandwidth value.
Indication to decrease CR or A for the connection
A congestion notification step of issuing an instruction to prohibit an increase in CR to the transmission terminal corresponding to the connection;
It is characterized by having.

According to a twenty-third aspect, information is transmitted between a transmitting terminal and a receiving terminal by an ATM communication network accommodating one or a plurality of connections for transferring information in a fixed-length cell using an ABR service category. When transmitted, the A
A flow control method performed between a communication element included in a TM communication network and said transmitting terminal and said receiving terminal, wherein cells transmitted in each of said connections are multiplexed and temporarily stored. A congestion determining step of determining whether or not congestion occurs in the queue; and an ACR value which is an ACR value for each of the connections based on information contained in cells transmitted to each of the connections and arriving at the queue. AC to calculate
R calculation step; ACR maximum value calculation step for obtaining an ACR maximum value that is the maximum value of the ACR values for each of the connections; and ACR maximum value for each of the connections and the ACR maximum value determined in advance from the ACR maximum value. An ACR comparison step of comparing an ACR threshold defined as a value reduced by the constant value obtained by the above, and when it is determined that the congestion occurs in the congestion determination step, based on a comparison result in the ACR comparison step, A congestion notification step of issuing an instruction to decrease the ACR or an instruction to prohibit an increase in the ACR to the transmitting terminal corresponding to the connection in which the ACR value is larger than the ACR threshold value. And

According to a twenty-fourth aspect, information is transmitted between a transmitting terminal and a receiving terminal by an ATM communication network accommodating one or more connections for transferring information in a fixed-length cell using an ABR service category. When transmitted, the A
A method of flow control performed between a communication element included in a TM communication network and said transmitting terminal and said receiving terminal, wherein cells transmitted in each of said connections are multiplexed and temporarily stored. A congestion determining step of determining whether or not congestion occurs in a queue; and a cell input from the transmitting terminal corresponding to each of the connections based on the number of cells transmitted in each of the connections and arriving at the queue. An input rate calculation step of calculating a rate, and an input rate maximum value calculation step of obtaining an input rate maximum value that is a maximum value of the cell input rates for each of the connections.
An input rate comparison step of comparing the cell input rate for each of the connections and an input rate threshold defined as a value obtained by subtracting a predetermined constant value from the input rate maximum value, and the congestion determination step In the case where it is determined that the congestion occurs,
An AC that is an input permission rate for a connection in which the input rate value is larger than the input rate threshold value, based on the comparison result in the input rate comparison step.
Indication to decrease R or AC for the connection
A congestion notification step of issuing an instruction to prohibit an increase in R to the transmitting terminal corresponding to the connection.

According to a twenty-fifth aspect, information is transmitted between a transmitting terminal and a receiving terminal by an ATM communication network accommodating one or a plurality of connections for transferring information in the form of fixed-length cells using an ABR service category. When transmitted, the A
A method of flow control performed between a communication element included in a TM communication network and said transmitting terminal and said receiving terminal, wherein cells transmitted in each of said connections are multiplexed and temporarily stored. A congestion determining step of determining whether or not congestion occurs in the queue;
R based on information contained in cells transmitted on each of the R service connections and arriving at the queue.
An ACR calculation step of calculating an ACR value Vacr for each of the R service connections; i1 <i2
T (i1) <T (i for integers i1 and i2
2) Level thresholds T (0), T (1),..., T, which are n constants set in advance to satisfy the relationship
Based on (n-1), for the integer i satisfying 0 ≦ i ≦ n−1, the ACR of the ABR service connection
The value of ACR for a connection whose value Vacr is greater than the level threshold value T (i) is equal to the level threshold value T (i).
The total value of the ACR values of the ABR service connection assuming that (i) is equal to the virtual ACR total value TA
A step of calculating a virtual ACR total value calculated as CR (i); and, if TACR (0)> Tg_Rin with respect to a preset input rate target value Tg_Rin, AB
Select all R service connections and TACR (j)
> Tg_Rin ≧ TACR (j−1) 1 ≦ j ≦ n−
If there is an integer j equal to 1, TACR (j)> Tg
A connection in which the ACR value Vacr is larger than a level threshold T (j-1) corresponding to an integer smaller by 1 than an integer j satisfying _Rin≥TACR (j-1) from the ABR service connection And TACR
(J)> When there is no integer j satisfying Tg_Rin, the value of the ACR Va is larger than the level threshold T (n-1).
a connection selecting step of selecting a connection having a large cr from the ABR service connections;
When it is determined in the congestion determination step that the congestion occurs, an instruction to reduce the ACR for the selected connection to the transmitting terminal corresponding to the connection selected in the connection selection step or an ACR for the connection A congestion notification step of issuing an instruction to prohibit an increase in

According to a twenty-sixth aspect, information is transmitted between a transmitting terminal and a receiving terminal by an ATM communication network accommodating one or a plurality of connections for transferring information in a fixed-length cell using an ABR service category. When transmitted, the A
A method of flow control performed between a communication element included in a TM communication network and said transmitting terminal and said receiving terminal, wherein cells transmitted in each of said connections are multiplexed and temporarily stored. A congestion determining step of determining whether or not congestion occurs in the queue;
An input rate calculating step of calculating an input rate Rcin of a cell from the transmitting terminal corresponding to each of the connections based on a number of cells transmitted to each of the R service connections and arriving at the queue; i1
T (i1) <T for integers i1 and i2 <i2
(I2) level thresholds T (0), T (1),..., Which are n constants set in advance to satisfy the relationship
Based on T (n-1), for an integer i such that 0 ≦ i ≦ n−1, cell input to a connection of the ABR service connections in which the input rate Rcin is greater than a level threshold T (i) A virtual input rate total value calculating step of calculating a total input rate of cells for the ABR service connection as a virtual input rate total value TRcin (i), assuming that the rate is equal to the level threshold value T (i); And TRcin (0) with respect to a preset input rate target value Tg_Rin.
> Tg_Rin, select all the ABR service connections, and TRcin (j)> Tg_Rin ≧ TR
When there is an integer j satisfying 1 ≦ j ≦ n−1 that satisfies cin (j−1), TRcin (j)> Tg_Rin ≧ TRc
A connection in which the input rate Rcin is higher than a level threshold T (j-1) corresponding to an integer smaller by 1 than an integer j that satisfies in (j-1) is selected from the ABR service connections, and TRcin (J)>
If there is no integer j that satisfies Tg_Rin, in the connection selecting step of selecting from the ABR service connections a connection in which the input rate Rcin is greater than the level threshold T (n-1), and in the congestion determining step If it is determined that the congestion occurs, the transmission terminal corresponding to the connection selected in the connection selection step is provided with an input permission rate A for the selected connection.
Indication to decrease CR or A for the connection
A congestion notification step of issuing an instruction to prohibit an increase in CR.

[0079]

Embodiments of the present invention will be described below with reference to the accompanying drawings. First Embodiment First, a flow control method according to a first embodiment of the present invention will be described. FIG. 1 shows an AT including a communication element for executing a flow control method according to the present embodiment.
FIG. 2 is a block diagram illustrating a configuration of an M communication network. The communication network comprises terminals 120, 130, 140 and communication elements 100,
110. The communication element 100 includes a queue 10
1, the parameter observation unit 102, and the queue length observation unit 10
3, a congestion determination unit 104, an FRTT calculation unit 105,
A CCR observation unit 106, a timeout detection unit 107,
An ACR calculation unit 108, an ACR total value calculation unit 109,
It includes an ACR total value threshold value calculation unit 111, a congestion occurrence prediction unit 112, and an EFCI bit setting unit 113. The communication element 110 and the communication element 100 are connected by a communication path, and the terminals 120, 130, and 140 respectively
It is connected to the communication element 100 via a communication path. In this example, the communication element 11 is transmitted from the transmission terminal accommodated in each of the terminals 120, 130, and 140 through the communication element 100.
The information is transferred in the form of a cell to the receiving terminal in the 0 direction. These cells are multiplexed in the queue 101 of the communication element 100 and output to the communication element 110. In addition,
In this example, only one configuration for multiplexing is shown, but a similar configuration is required for each portion where cells are multiplexed and congestion occurs.

Next, the operation of each part of the communication element 100 will be described. When a cell is input from a communication channel, the queue 101 stores the cell at the end of the queue. In addition, at a predetermined time interval, the first cell among the stored cells is output to EFCI bit setting section 113. Also, the queue 101 outputs a queue length increase signal to the queue length observation unit 103 immediately after a cell is input from the communication channel. Immediately after outputting the cell to the EFCI bit setting unit 113, the queue 101 outputs a queue length decrease signal to the queue length observation unit 103.

The queue length observation unit 103 calculates the queue length L_que
Manage. That is, when the queue length observation unit 103 receives the queue length increase signal from the queue 101, the queue length L_q
ue is increased by 1 and the queue length decrease signal is sent to the queue 101.
, The queue length L_que is decreased by one, and the queue length L_que is increased or decreased by one, and then the value of the queue length L_que is output to the congestion determination unit 104 and the congestion prediction threshold calculation unit 111. However, when the operation of the communication element 100 starts, the queue length L_que is set to “0”. When the queue length L_que is equal to the buffer capacity S_buf, which is the maximum number of cells that can be stored in the queue 101, the value of the queue length L_que does not increase even if a queue length increase signal is received.

When a cell arrives at queue 101, FRTT calculating section 105 determines the VPI field and VCI of the cell.
Determine the type of cell from the contents of the field. And
If the cell arriving at the queue 101 is a signaling cell used for setting up an ABR service connection,
From the content of the signaling cell, the FR of the connection
Calculate the value of TT (Fixed Round-Trip Time) and connection number CN, and use them for ACR total value threshold value calculation unit 1
11 is output.

Here, FRTT is the delay time from when the communication element issues an instruction to increase or decrease the input rate to the ABR service connection, until the input rate at the communication element changes in response to the instruction. Is a parameter indicating the value. In addition, when a connection is established, a signaling cell is reciprocated between a transmitting terminal and a receiving terminal, and a communication element passing therethrough and a delay time in a transmission path are sequentially added to obtain a value of the FRTT. Stipulated in

The congestion judging section 104 includes the queue length calculating section 10
When the queue length L_que is received from No. 3, the value is compared with a preset congestion determination threshold value. Based on the result of the comparison, the congestion determination unit 104 sends the congestion determination signal to the EFCI bit setting unit 1 if the queue length L_que is larger.
13, and outputs a non-congestion determination signal to the EFCI bit setting unit 113 when the congestion determination threshold is larger.

When a cell arrives at queue 101, CCR observation section 106 determines the type of the cell by observing the contents of the PTI field of the cell. If the cell that has arrived at the queue is an RM cell, the CC
The R observation unit 106 observes the CCR value written in the CCR field (Current Cell Rate field) of the received RM cell, and observes the contents of the VCI field and the VPI field of the received RM cell to thereby check the RM cell. Is calculated. Then, the CCR value and the connection number CN are stored in A
Output to CR calculating section 108. At the same time, CCR observation section 106 outputs connection number CN of the received RM cell to timeout detection section 107.
However, in the ABR service, when the transmitting terminal transmits an RM cell, the value of the ACR at that time is set to the CRM of the RM cell.
It is stipulated that writing is performed in the CR field.

The parameter observing section 102 has a queue 101
The cell type is determined by observing the value of the PTI field of the cell when the cell arrives at. If the cell arriving at the queue 101 is a signaling cell used for setting up an ABR service connection, the parameter observing section 102 analyzes the contents of the cell to obtain ICR and ACR control parameters for the ABR service. ADTF (ACR Decrease Time Fac
tor) and the connection number CN are detected. And
The ICR value and the connection number CN are calculated by the ACR calculation unit 10.
8, the ADTF value and the connection number C
N is output to the timeout detection unit 107.

Upon receiving the connection number CN and the value of ADTF from the parameter observing section 102, the timeout detecting section 107 stores the received ADTF value in association with the received connection number CN. Further, the timeout detection unit 107 has a timer for each ABR service connection. Upon receiving the connection number CN from the CCR observation unit 106, the timeout detection unit 107 initializes the timer value of the corresponding timer to “0”. Start the timer and measure the time elapsed since that time. Then, when the timer value becomes equal to the value of ADTF of the connection, the connection number CN is output to ACR calculating section 108.

The ACR calculator 108 calculates the connection number C of each connection using the ABR service.
The ACR value and the ICR value are managed corresponding to N. A
Upon receiving the values of the connection number CN and the ICR from the parameter observation unit 102, the CR calculation unit 108 newly secures a storage area for managing the ICR and the ACR corresponding to the received connection number CN, and The value of the ACR is set to the value of the received ICR. Then, ACR calculating section 108 outputs the received connection number CN and the corresponding ACR value (equal to the received ICR) to ACR total value calculating section 109.

Further, upon receiving the connection number CN and the CCR value from the CCR observation section 106, the ACR calculation section 108 receives the AC number corresponding to the received connection number CN.
Update the R value to the received CCR value, and then
The value and the connection number CN are calculated by the ACR total value calculation unit 109.
Output to Further, upon receiving the connection number CN from the timeout detection unit 107, the ACR calculation unit 108 updates the ACR value corresponding to the received connection number CN with the ICR value of the connection,
After that, the ACR value and the connection number CN are output to the ACR total value calculation unit 109.

The ACR total value calculation unit 109 calculates the ACR total value for each connection using the ABR service.
Manage values. The ACR total value calculation unit 109 calculates
When the ACR value and the connection number CN are received from the R calculation unit 108, the managed ACR value is updated to the received value. Thereafter, the ACR total value calculation unit 109 calculates the total ACR value for each connection to obtain the ACR total value TACR, and obtains the ACR total value TAC.
R is output to the congestion occurrence prediction unit 112.

The ACR total threshold calculator 111 calculates a buffer capacity S_buf, which is the maximum number of cells that can be stored in the queue 101, and a queue output rate Ro defined as a reciprocal of a time interval at which the queue 101 outputs cells.
ut, and the FRTT value of each connection and the average value thereof, ie, the average value of the FRTT Av_FRTT, and
Queue length L, which is the number of cells stored in the queue 101
Stores the value of _que. Upon receiving the connection number CN and the value of the FRTT from the FRTT calculation unit 105, the ACR total value threshold value calculation unit 111 newly stores the value of the FRTT of the connection with the received connection number CN. After that, the average value of the FRTT of all the connections is calculated, and the calculated value is newly added to the average value of the FRTT Av_FRTT.
And the AC defined by the following relational expression (12):
Calculate the R total value threshold Th_TACR, and finally calculate the ACR
The total value threshold Th_TACR is output to the congestion occurrence prediction unit 112. Th_TACR = (S_buf−L_que) / Av_FRTT + Rout (12) Here, S_buf represents a buffer capacity, L_que represents a queue length, and Rout represents an output rate of the queue 101.

ACR total value threshold value calculating section 111
Receives the queue length L_que from the queue length observation unit 103, updates the stored value of the queue length L_que to the received value, and then calculates the ACR total value threshold Th_TACR according to the relational expression (12). , And outputs the calculated ACR total threshold value Th_TACR to the congestion occurrence prediction unit 112.

The congestion occurrence prediction unit 112 stores the ACR total value threshold Th_TACR and the ACR total value TACR. Upon receiving the ACR total threshold Th_TACR from the ACR total threshold calculator 111, the congestion occurrence prediction unit 112 updates the stored ACR total threshold Th_TACR to the received value, and updates the ACR total Value threshold Th_TACR
And the ACR total value TACR. Based on the comparison result, the congestion occurrence prediction unit 112 calculates the ACR total value TAC
If R is larger, a congestion prediction signal is output to EFCI bit setting section 113. Conversely, if ACR total value threshold Th_TACR is larger, a non-congestion prediction signal is output to EFCI bit setting section 113. 113 is output. on the other hand,
Upon receiving the ACR total value TACR from the ACR total value calculation unit 109, the congestion occurrence prediction unit 112 updates the stored ACR total value TACR to the received value,
The total value threshold Th_TACR is compared with the ACR total value TACR. Based on the comparison result, the congestion occurrence prediction unit 112
Outputs a congestion prediction signal to the EFCI bit setting unit 113 when the ACR total value TACR is larger, and outputs the congestion prediction signal when the ACR total value threshold Th_TACR is larger.
A non-congestion prediction signal is output to EFCI bit setting section 113.

The congestion occurrence prediction unit 112 predicts the occurrence of congestion when the total ACR value TACR is larger than the total ACR threshold value Th_TACR. ｛TACR-R
out｝ × Av_FRTT> S_buf−L_que The left side of the above relational expression indicates the amount of increase in the queue length when the input rate becomes equal to the total ACR value TACR. Therefore, it is understood that the occurrence of congestion is predicted if there is a possibility of buffer overflow when the input rate becomes equal to the ACR total value TACR.

The EFCI bit setting section 113 manages a congestion determination flag Fcg and a congestion prediction flag Fp_cg. The congestion determination flag Fcg is a flag indicating whether or not congestion has been detected in the queue 101, and Fcg = "1" means that congestion has been detected (the same applies to the following embodiments). The congestion prediction flag Fp_cg is
01 is a flag indicating whether or not congestion is predicted to occur. Fp_cg = "1" means that congestion is predicted to occur (the same applies to the following embodiments). The EFCI bit setting unit 113 sets the congestion determination unit 10
When the congestion judgment signal is received from the congestion judgment unit 104, the congestion judgment flag Fcg is set to "1".
When receiving the congestion prediction signal from the congestion occurrence prediction unit 112, the EFCI bit setting unit 113 sets the congestion prediction flag F
When p_cg is set to “1” and a non-congestion prediction signal is received from the congestion occurrence prediction unit 112, the congestion prediction flag Fp_cg is set to “0”.
Set to. Further, the EFCI bit setting unit 113
When a data cell is received from the queue 101, if the value of the congestion determination flag Fcg or the congestion prediction flag Fp_cg is "1", the EFCI bit of the data cell is set to "1", and the congestion determination flag Fcg and the congestion prediction flag are set. When the values of Fp_cg are both “0”, the value of the EFCI bit of the data cell is not changed. After that, the EFCI bit setting unit 113 outputs the data cell to the communication element 110. However, the values of the congestion determination flag Fcg and the congestion prediction flag Fp_cg managed by the EFCI bit setting unit 113 are:
When the operation of the communication element 100 is started, both are set to “0”.

In the flow control method according to the present embodiment, the congestion prediction flag Fp_cg is introduced as described above, and the EFCI bit in the data cell is set based on the congestion prediction flag Fp_cg in addition to the congestion determination flag F_cg.
In this point, the present embodiment is different from the conventional flow control method. Therefore, in the following, this congestion prediction flag F
The setting operation of p_cg will be described.

FIG. 2 is a flowchart showing a procedure for setting the congestion prediction flag Fp_cg in the communication element 100 (hereinafter referred to as “congestion prediction flag setting procedure”). In this flowchart, ACR [CN] represents the value of the ACR for the connection with the connection number CN, the timer value [CN] represents the timer value of the timer corresponding to the connection with the connection number CN,
ICR [CN] represents the value of ICR for the connection with connection number CN, and ADTF [CN] represents the value of ADTF for the connection with connection number CN.

As shown in FIG. 2, this congestion prediction flag setting procedure is started when any of the following events i) to iii) occurs. i) Arrival of a cell to the queue 101 (hereinafter referred to as “cell arrival”) ii) Output of a cell from the queue 101 (hereinafter “cell output”)
Iii) The timer value of the timer corresponding to one of the connections is equal to the ADTF value of the connection (hereinafter referred to as "timeout").

First, a case where the procedure for setting a congestion prediction flag is activated by cell arrival will be described. Queue 10
1 (step S100), the queue 1
01, a queue length increase signal is output, and the queue length observation unit 103 that has received the queue length increase signal increases the queue length L_que by 1 (step S102). Note that, as described above, the queue length L_que is
It is set to “0” when the operation of “0” starts.

After that, the type of the cell arriving at the queue 101 is determined by the FRTT calculation unit 105 and the parameter observation unit 1.
02 and the CCR observation unit 106 are determined (step S104). As a result, the cell becomes A
If the cell is a signaling cell for setting a BR service connection, the following processing is performed. That is,
FRTT value of the connection and connection number C
N is calculated by the FRTT calculation unit 105 (step S106). Also, the ICR value of the connection and the connection number CN are detected from the cell in the parameter observation unit 102 (step S108).
Using the value of this ICR and the connection number CN,
The R calculation unit 108 sets the ACR value of the connection to the ICR value (step S10).
8). This ACR value and connection number CN are ACR
It is output to total value calculation section 109.

When the values of the connection number CN and the FRTT are calculated by the FRTT calculating section 105, the FRTT is calculated.
Using the value of T, the ACR total threshold calculating unit 111 calculates the average value Av_FRTT of the FRTTs of all the connections (step S110).

When the ACR value and the connection number CN are output from the ACR calculation unit 108, the ACR total value calculation unit 109 calculates the sum of the ACR values for each connection by using the ACR value.
An R total value TACR is obtained (step S152).

When the FRTT value is output together with the connection number CN from the FRTT calculating section 105, or the queue length L_que is output from the queue length observing section 103, the ACR total value is calculated using the equation (12). In the threshold value calculation unit 111, the ACR total value threshold value Th_TACR
Is calculated (step S154).

The above ACR total value TACR and the above AC
The R total value threshold Th_TACR is the congestion occurrence prediction unit 112
Are compared (step S156). According to the comparison result, the congestion prediction flag Fp_cg is set in the EFCI bit setting unit 113. That is, when the ACR total value TACR is smaller than the ACR total value threshold value Th_TACR, the congestion prediction flag Fp_cg is set to “0” (step S158), and the ACR total value TACR becomes
If it is larger than the total value threshold Th_TACR, the congestion prediction flag Fp_cg is set to "1" (step S16).
0). By the way, when the ACR total value TACR is larger than the ACR total value threshold Th_TACR, as described above, {TACR-Rout} × Av_FRTT> S_buf-L_que, so that the input rate is equal to the ACR total value TACR. When this happens, the buffer may overflow. Therefore, if the congestion prediction flag Fp_cg is "1", it can be determined that there is a possibility of cell discarding when cells are input at a rate equal to ACR in all connections.

When the congestion prediction flag Fp_cg is set in this way, the congestion prediction flag setting procedure ends.

The type of the cell arriving at the queue 101 is determined by the CCR observation unit 106 (step S10).
4, S122), as a result, if the cell is an RM cell, CCR observing section 106 obtains a CCR value from the RM cell and calculates a connection number CN corresponding to the RM cell (step S122). S124).
This connection number CN is used as the timeout detection unit 107
Is output to The CCR value and the connection number CN are output to the ACR calculation unit 108, and the ACR calculation unit 1
At 07, the value of the ACR of the connection is
The value is updated to the CR value (step S126). This ACR
Is output to the ACR total value calculation unit 109 together with the connection number CN.

When the connection number CN is output to the timeout detection unit 107, the timer starts after the timer value of the timer corresponding to the connection number CN is initialized to “0” (step S1).
28).

The ACR value and the connection number CN
Is output to the ACR total value calculation unit 109, the ACR total value calculation unit 109 calculates the total of ACR values for each connection using the ACR value, and thereby obtains the ACR total value TACR (step S1
52).

Thereafter, the same processing as when the cell arriving at the queue 101 is a signaling cell (steps S154 to S160) is performed, and the ACR total values TACR and ACR are obtained.
The congestion prediction flag Fp_cg is set according to the result of comparison with the CR total value threshold Th_ACR, and the congestion prediction flag setting procedure ends.

As a result of the determination in step S122,
If the cell arriving at the queue 101 is not an RM cell, that is, if a data cell has arrived at the queue 101, the process proceeds to step S154, and the ACR total threshold calculator Th_TACR calculates the ACR total threshold Th_TACR. Is done. Thereafter, by the same processing as when the cell arriving at the queue 101 is a signaling cell or an RM cell (steps S156 to S160), the AC
The congestion prediction flag Fp_cg is set according to the comparison result between the R total value TACR and the ACR total value threshold Th_ACR, and the congestion prediction flag setting procedure ends.

Next, a case where the congestion prediction flag setting procedure is started due to a timeout will be described. In the aforementioned step S128, after the timer corresponding to a certain connection is initialized with its timer value set to "0" and started, if the elapsed time from the start time, that is, the timer value becomes equal to the value of ADTF of the connection. (S130), the connection number CN of the connection is output from the timeout detection unit 107 to the ACR calculation unit 108. If this connection number CN is AC
When received by the R calculation unit 108, the ACR value corresponding to the connection number CN is set to the value of the ICR of the connection (step S132). This A
The value of CR is output to ACR total value calculation section 109 together with the connection number CN.

The ACR value and the connection number CN
Is output to the ACR total value calculation unit 109, the ACR total value calculation unit 109 calculates the total of ACR values for each connection using the ACR value, and thereby obtains the ACR total value TACR (step S1
52).

Thereafter, the same processing as when the congestion prediction flag setting procedure is started by the arrival of the cell (steps S154 to S160), the ACR total value TACR and the ACR
The congestion prediction flag Fp_cg is set according to the comparison result with the total value threshold Th_ACR, and the congestion prediction flag setting procedure ends.

Next, a case where the congestion prediction flag setting procedure is activated by cell output will be described. When a cell is output from the queue 101 to the ECFI bit setting unit 113 (step S140), a queue length reduction signal is output from the queue 101, and the queue length observation unit 103 that has received the queue length reduction signal changes the queue length L_que. Decrease by 1 (step S142).

Thereafter, using the queue length L_que, AC
The ACR total value threshold Th_TACR is calculated by the R total value threshold calculator 111 (step S154).

Thereafter, the same processing as when the congestion prediction flag setting procedure is started by the arrival of the cell (steps S156 to S160), the ACR total value TACR and the ACR
The congestion prediction flag Fp_cg is set according to the comparison result with the total value threshold Th_ACR, and the congestion prediction flag setting procedure ends.

The EFCI bit setting unit 113 sets the congestion prediction flag Fc_cg based on the congestion determination signal from the congestion determination unit 104 in addition to the setting of the congestion prediction flag Fp_cg based on the congestion prediction flag setting procedure described above. I do. When the EFCI bit setting unit 113 receives the data cell from the queue 101 as described above, the EFCI bit of the data cell is set to “1” when the value of the congestion determination flag Fcg or the congestion prediction flag Fp_cg is “1”. When the value is set to “1” and the values of the congestion determination flag Fcg and the congestion prediction flag Fp_cg are both “0”, the value of the EFCI bit of the data cell is not changed. Then, the EFCI bit setting unit 1
13 outputs the data cell to the communication element 110. Such setting of the EFCI bit instructs the transmitting terminal to increase or decrease the ACR value.

As described above, in the present embodiment, when the congestion prediction flag Fp_cg is “1”, the EFC of the data cell is independent of the value of the congestion determination flag Fcg.
Setting the I bit to “1” instructs the transmitting terminal to reduce the ACR value. That is, according to the present embodiment, by calculating the ACR value of each connection, the total value of the input rates when all the connections input at a rate equal to the ACR is calculated as the ACR total value TACR, If it is determined that cell discarding may occur when cell input is performed at the input rate, the input rate of each connection decreases. As a result, even when a connection that is not currently performing cell input rapidly increases the input rate to the value of ACR, the possibility of cell discarding is reduced. Therefore, according to the present embodiment, even when the present invention is applied to multiplexing of connections that generate data having a large burst property, the possibility of cell loss can be reduced.

In the above embodiment, when the congestion determination flag Fcg is “0” and the congestion prediction flag Fp_cg is “1”, the EFCI bit of the data cell is set to “1” so that ACR reduction is instructed. Alternatively, when the congestion determination flag Fcg is “0” and the congestion prediction flag Fp_cg is “1”, the RM cell May be instructed to the transmitting terminal by setting the NI bit of "1" to "1".

<Second Embodiment> Next, a flow control method according to a second embodiment of the present invention will be described. FIG.
FIG. 1 is a block diagram illustrating a configuration of an ATM communication network including a communication element that executes a flow control method according to an embodiment.
This communication network includes terminals 220, 230, 240 and communication elements 200, 210. The communication element 200
Queue 201, parameter observing section 202, queue length observing section 203, congestion determining section 204, FRTT calculating section 205, CCR observing section 206, timeout detecting section 207, ACR calculating section 208, maximum input cell It includes a number prediction unit 209, a congestion prediction threshold calculation unit 211, a congestion occurrence prediction unit 212, and an EFCI bit setting unit 213. The communication element 210 and the communication element 200 are connected by a communication path, and the terminals 220, 230, and 240 are respectively connected to the communication element 200 by a communication path. In this example, information is transferred in the form of a cell from a transmitting terminal accommodated in each of the terminals 220, 230, 240 to a receiving terminal in the direction of the communication element 210 through the communication element 200. Each of these cells is stored in the queue 201 of the communication element 200.
And output to the communication element 210. Although only one configuration for multiplexing is shown in this example, a similar configuration is required for each part where cells are multiplexed and congestion occurs.

Next, the operation of each part of the communication element 200 will be described. When a cell is input from a communication channel, the queue 201
Save the cell at the end of the queue. Also, at a predetermined time interval, the first cell among the stored cells is output to the EFCI bit setting unit 213. Also, the queue 201 outputs a queue length increase signal to the queue length observation unit 203 immediately after a cell is input from the communication channel. The queue 201 outputs a queue length decrease signal to the queue length observation unit 203 immediately after outputting the cell to the EFCI bit setting unit 213.

The queue length observation unit 203 calculates the queue length L_que
Manage. That is, when the queue length observation unit 203 receives the queue length increase signal from the queue 201, the queue length L_q
ue is increased by 1 and the queue length decrease signal is sent to the queue 201.
, The queue length L_que is decreased by one, and the queue length L_que is increased or decreased by one. However, when the operation of the communication element 200 is started, the queue length L_que is set to “0”. When the queue length L_que is equal to the buffer capacity S_buf, which is the maximum number of cells that can be stored in the queue 201, the value of the queue length L_que does not increase even if the queue length increase signal is received.

When a cell arrives at the queue 201, the FRTT calculating section 205 determines the VPI field of the cell and the VCI
Determine the type of cell from the contents of the field. And
If the cell arriving at the queue 201 is a signaling cell used for setting up an ABR service connection,
From the content of the signaling cell, the FR of the connection
Calculate the value of TT and the connection number CN, and use them as the congestion prediction threshold value calculation unit 211 and the maximum input cell number prediction unit 2
09 is output.

[0124] Here, the FRTT is the delay time from when the communication element issues an instruction to increase or decrease the input rate to the ABR service connection, until the input rate at the communication element changes in response to the instruction. Is a parameter indicating the value. Also, when a connection is set up, a signaling cell is reciprocated between a transmitting terminal and a receiving terminal, and a communication element passing therethrough and a delay time in a transmission path are sequentially added to obtain a value of FRTT. Stipulated in

The congestion judging section 204 is composed of the queue length calculating section 20
When the queue length L_que is received from No. 3, the value is compared with a preset congestion determination threshold value. Based on the result of the comparison, the congestion determination unit 204 transmits the congestion determination signal to the EFCI bit setting unit 2 when the queue length L_que is larger.
13 and outputs a non-congestion determination signal to the EFCI bit setting unit 213 when the congestion determination threshold is larger.

When a cell arrives at the queue 201, the CCR observation unit 206 determines the type of the cell by observing the contents of the PTI field of the cell. If the cell that has arrived at the queue is an RM cell, the CC
The R observation unit 206 observes the CCR value written in the CCR field (Current Cell Rate field) of the received RM cell, and observes the contents of the VCI field and the VPI field of the received RM cell, thereby obtaining the RM cell. Is calculated for the connection number CN. Then, it outputs the CCR value and connection number CN to ACR calculation section 208. At the same time, the CCR observation unit 206 outputs the connection number CN of the received RM cell to the timeout detection unit 207. However, in the ABR service, the transmitting terminal is RM
When transmitting a cell, it is specified that the value of the ACR at that time be written in the CCR field of the RM cell.

The parameter observing unit 202
The cell type is determined by observing the value of the PTI field of the cell when the cell arrives at. If the cell arriving at the queue 201 is a signaling cell used for setting up an ABR service connection, the parameter observing unit 202 analyzes the contents of the cell to obtain ICR and ACR service control parameters. The value of ADTF and the connection number CN are detected. Then, it outputs the value of ICR and connection number CN to ACR calculating section 208, and outputs
And the connection number CN to the timeout detection unit 20
7 is output.

Upon receiving the connection number CN and the value of ADTF from the parameter observing section 202, the timeout detecting section 207 stores the received value of ADTF in association with the received connection number CN. Further, the timeout detection unit 207 has a timer for each ABR service connection, and upon receiving the connection number CN from the CCR observation unit 206, initializes the timer value of the corresponding timer to “0”, Start the timer and measure the time elapsed since that time. Then, when the timer value becomes equal to the value of ADTF of the connection, the connection number CN is output to the ACR calculation section 208.

[0129] The ACR calculator 208 calculates the connection number C of each connection using the ABR service.
The ACR value and the ICR value are managed corresponding to N. A
Upon receiving the values of the connection number CN and the ICR from the parameter observing unit 202, the CR calculation unit 208 newly secures a storage area for managing the ICR and the ACR corresponding to the received connection number CN, and The value of the ACR is set to the value of the received ICR. Then, for the maximum input cell number prediction unit 209, the received connection number CN and the corresponding ACR
Output value (equal to received ICR).

When the ACR calculation section 208 receives the connection number CN and the CCR value from the CCR observation section 206, the ACR calculation section 208 receives the AC number corresponding to the received connection number CN.
Update the R value to the received CCR value, and then
The value and the connection number CN are entered into the maximum input cell number prediction unit 20.
9 is output. Further, the ACR calculation unit 208
When the connection number CN is received from the timeout detection unit 207, the ACR value corresponding to the received connection number CN is updated to the value of the ICR of the connection, and then the ACR value and the connection number CN are set to the maximum input cell number prediction unit 209. Output to

The maximum input cell number prediction unit 209 calculates the FRTT
When receiving the connection number CN and the value of the FRTT from the calculation unit 205, it stores the received value of the FRTT in association with the received connection number CN. The maximum input cell number prediction unit 209 manages a maximum input cell number prediction value for each connection using the ABR service. The maximum input cell number prediction unit 209 calculates AC
When the ACR value and the connection number CN are received from the R calculation unit 208, the maximum input cell is calculated by calculating the product of the received ACR value and the value of the FRTT corresponding to the received connection number CN, that is, by the following equation. The number prediction value Np_maxin is calculated. Np_maxin = ACR ×
FRTT and this maximum input cell number predicted value Np_maxin
Is stored in association with the connection number CN. After that, by calculating the total of the maximum input cell number prediction values Np_maxin for each connection, that is, by the following equation, the total maximum input cell number prediction value TNp_maxin is obtained, and the value is output to the congestion occurrence prediction unit 212. I do. TNp_maxin = ΣNp_maxin However, “Σ” in the above equation means that the sum of the following items for all connections is calculated.

The congestion prediction threshold value calculation unit 211 calculates the buffer capacity S_buf, which is the maximum number of cells that can be accumulated in the queue 201, and the queue output rate Rout defined as the reciprocal of the time interval at which the queue 201 outputs cells.
, And the FRTT value of each connection and the average value thereof, ie, the FRTT average value Av_FRTT, and the queue length L_queue, which is the number of cells accumulated in the queue 201.
Is stored. Congestion prediction threshold calculator 211
Receives the connection number CN and the value of the FRTT from the FRTT calculating unit 205, and newly stores the value of the FRTT of the received connection. After that, the average value of the FRTT of all the connections is calculated, the value is newly stored as the average value of the FRTT Av_FRTT, and the congestion prediction threshold value PTh_cg defined by the following relational expression (13) is calculated. The congestion prediction threshold value PTh_cg is output to the congestion occurrence prediction unit 212. PTh_cg = Rout × Av_FRTT + S_buf−L_que (13) Here, S_buf represents a buffer capacity, L_que represents a queue length, and Rout represents an output rate of the queue 101.

Also, the congestion prediction threshold value calculation unit 211
Upon receiving the queue length L_que from the queue length observation unit 203, the stored queue length L_que is updated to the received value, and then the congestion prediction threshold value PTh_cg is calculated and calculated according to the relational expression (13). Congestion prediction threshold value PTh_
cg is output to the congestion occurrence prediction unit 212.

The congestion occurrence prediction unit 212 stores a congestion prediction threshold value PTh_cg and a total maximum input cell number prediction value TNp_maxin. Upon receiving the congestion prediction threshold value PTh_cg from the congestion prediction threshold value calculation unit 211, the congestion occurrence prediction unit 212 updates the stored congestion prediction threshold value PTh_cg to the received value, and sets the congestion prediction threshold value PTh_cg. And the total maximum input cell number prediction value TNp_maxin. Based on the comparison result, the congestion occurrence prediction unit 212 outputs a congestion prediction signal to the EFCI bit setting unit 213 when the total maximum input cell number prediction value TNp_maxin is larger,
When the congestion prediction threshold value PTh_cg is larger, a non-congestion prediction signal is output to the EFCI bit setting unit 213. On the other hand, the congestion occurrence prediction unit 212 obtains the total maximum input cell number prediction value TNp_maxin from the maximum input cell number prediction unit 209.
Is received, the stored total maximum input cell number prediction value TNp_maxin is updated to the received value, and the congestion prediction threshold value PTh_cg is compared with the total maximum input cell number prediction value TNp_maxin. Based on the comparison result, the congestion occurrence prediction unit 1
12, when the total maximum input cell number prediction value TNp_maxin is larger, the congestion prediction signal
3 and the congestion prediction threshold value PTh_cg is larger, the non-congestion prediction signal is output to the EFCI bit setting unit 21.
3 is output.

Here, when the occurrence of congestion is predicted by the congestion occurrence prediction section 212, the total maximum input cell number prediction value TNp_maxin is larger than the congestion prediction threshold value PTh_cg. It looks like this: TNp_maxin−Rout × Av_FRTT> S_buf−L_que The left side of the above relational expression is the total maximum input cell number prediction value TNp
Indicates the increase in queue length when there are cell inputs equal to _maxin. Therefore, the total maximum input cell number prediction value T
It can be seen that if there is a possibility of buffer overflow when there are cell inputs equal to Np_maxin, occurrence of congestion is predicted.

The EFCI bit setting section 213 manages a congestion determination flag Fcg and a congestion prediction flag Fp_cg. Then, the EFCI bit setting unit 213 determines whether the congestion determination unit 20
When the congestion judgment signal is received from the congestion judgment unit 204, the congestion judgment flag Fcg is set to "0".
When receiving the congestion prediction signal from the congestion occurrence prediction unit 212, the EFCI bit setting unit 213 sets the congestion prediction flag F
When p_cg is set to “1” and a non-congestion prediction signal is received from the congestion occurrence prediction unit 212, the congestion prediction flag Fp_cg is set to “0”.
Set to. Further, the EFCI bit setting unit 213
When a data cell is received from the queue 201, if the value of the congestion determination flag Fcg or the congestion prediction flag Fp_cg is “1”, the EFCI bit of the data cell is set to “1”, and the congestion determination flag Fcg and the congestion prediction flag are set. When the values of Fp_cg are both “0”, the value of the EFCI bit of the data cell is not changed. After that, the EFCI bit setting unit 213 outputs the data cell to the communication element 210. However, the values of the congestion determination flag Fcg and the congestion prediction flag Fp_cg managed by the EFCI bit setting unit 213 are as follows:
When the operation of the communication element 200 is started, both are set to “0”.

In the flow control method according to the present embodiment, the congestion prediction flag Fp_cg is introduced as described above, and the EFCI bit in the data cell is set based on the congestion prediction flag Fp_cg in addition to the congestion determination flag F_cg.
In this point, the present embodiment is different from the conventional flow control method. Therefore, in the following, this congestion prediction flag F
The setting operation of p_cg will be described.

FIG. 4 is a flowchart showing the procedure of setting the congestion prediction flag Fp_cg in the communication element 200 (congestion prediction flag setting procedure). In this flowchart, ACR [CN] is the connection number C
NCR represents the value of ACR for the connection of N, timer value [CN] represents the timer value of the timer corresponding to the connection of connection number CN, ICR [CN] represents the value of ICR for the connection of connection number CN, and ADTF [ CN] represents the value of ADTF for the connection with connection number CN, and Np_maxin
[CN] represents the predicted value of the maximum number of input cells for the connection with the connection number CN.

In the congestion prediction flag setting procedure in the present embodiment shown in FIG. 4, steps S152 to S152 in the congestion prediction flag setting procedure in the first embodiment shown in FIG.
Step S160 is replaced with steps S250 to S260. Other steps S100 to S132, S140, and S in the congestion prediction flag setting procedure in the present embodiment.
142 is the same as the step in the congestion prediction flag setting procedure in the first embodiment, and the corresponding step is assigned the same step number. Hereinafter, the procedure for setting the congestion prediction flag in the present embodiment will be described focusing on the processing in steps S250 to S260.

The procedure for setting the congestion prediction flag in this embodiment is also started by any of the cell arrival (step S100), cell output (step S140), and timeout (step S130). In the congestion prediction flag setting procedure according to the first embodiment, when the congestion prediction flag setting procedure is started due to cell arrival or timeout, in step S152, the ACR total value is calculated. On the other hand, in this embodiment, in this case, AC
Instead of calculating the R total value, the maximum input cell number prediction value Np
_maxin is calculated by the maximum input cell number prediction unit 209 (step S250). This maximum input cell number predicted value N
p_maxin is the ACR output from the ACR calculation unit 208
Based on the value and the connection number CN, it is calculated by the following equation using the FRTT value corresponding to the connection number CN. Np_maxin = ACR × FRTT Thereafter, the maximum input cell number prediction unit 209 calculates the sum of the maximum input cell number prediction value Np_maxin for each connection, thereby obtaining the total maximum input cell number prediction value TNp_max.
in is calculated. This total maximum input cell number prediction value TNp
_maxin is output to the congestion occurrence prediction unit 212.

Next, the FRTT value is output together with the connection number CN from the FRTT calculating section 205, or
When the queue length L_que is output from the queue length observation unit 203, the connection number CN, the value of FRTT,
On the basis of the queue length L_que, the congestion prediction threshold PT
h_cg is calculated (S254). The queue length L_que is output from the queue length observing unit 203 when the congestion prediction flag setting procedure is activated by cell arrival or cell output. Is output.

The above total maximum input cell number prediction value TNp_m
axin is compared with the congestion prediction threshold value PTh_cg in the congestion occurrence prediction unit 212 (step S25).
6). According to the comparison result, the congestion prediction flag Fp_cg is set in the EFCI bit setting unit 113. That is, when the total maximum input cell number prediction value TNp_maxin is smaller than the congestion prediction threshold value PTh_cg, the congestion prediction flag Fp_cg is set to “0” (step S258),
If the total maximum input cell number prediction value TNp_maxin is larger than the congestion prediction threshold value PTh_cg, the congestion prediction flag F
p_cg is set to "1" (step S260). By the way, when the total maximum input cell number prediction value TNp_maxin is larger than the congestion prediction threshold value PTh_cg, TNp_maxin−Rout × Av_FRTT> S_buf−L_que. Buffer overflow when input occurs. Therefore, if the congestion prediction flag Fp_cg is “1”, the total maximum input cell number prediction value TNp_max
When there are cell inputs equal to in, it can be determined that cell discard may occur.

When the congestion prediction flag Fp_cg is set in this way, the congestion prediction flag setting procedure ends.

The EFCI bit setting section 213 sets the congestion prediction flag Fp_cg based on the congestion prediction flag setting procedure described above, and also sets the congestion determination flag Fcg based on the congestion determination signal from the congestion determination section 104 as in the conventional example. I do. Then, as described above, upon receiving a data cell from the queue 201, the EFCI bit setting unit 213 sets the EFCI bit of the data cell to “1” when the value of the congestion determination flag Fcg or the congestion prediction flag Fp_cg is “1”. When the value is set to “1” and the values of the congestion determination flag Fcg and the congestion prediction flag Fp_cg are both “0”, the value of the EFCI bit of the data cell is not changed. Then, the EFCI bit setting unit 2
13 outputs the data cell to the communication element 210. Such setting of the EFCI bit instructs the transmitting terminal to increase or decrease the ACR value.

As described above, in this embodiment, when the congestion prediction flag Fp_cg is "1", the EFC of the data cell is independent of the value of the congestion determination flag Fcg.
Setting the I bit to “1” instructs the transmitting terminal to reduce the ACR value. That is, according to the present embodiment, by calculating the ACR value of each connection, the maximum value of cells to be input when all connections have input at a rate equal to the ACR is predicted. If it is determined that cell discarding may occur when cell input is performed, the input rate of each connection decreases. As a result, even when a connection that is not currently performing cell input rapidly increases the input rate to the ACR value, the possibility of cell discarding is reduced.
Therefore, according to the present embodiment, even when the present invention is applied to multiplexing of connections that generate data having a large burst property, the possibility of cell loss can be reduced.

In the above embodiment, when the congestion determination flag Fcg is “0” and the congestion prediction flag Fp_cg is “1”, the EFCI bit of the data cell is set to “1” so that In order to prevent a sudden increase in the input rate when the congestion determination flag Fcg is "0" and the congestion prediction flag Fp_cg is "1", the RM cell May be set to "1" to instruct the transmitting terminal to prohibit an increase in the ACR.

<Third Embodiment> Next, a flow control method according to a third embodiment of the present invention will be described. FIG.
FIG. 1 is a block diagram illustrating a configuration of an ATM communication network including a communication element that executes a flow control method according to an embodiment.
This communication network includes terminals 320, 330, 340 and communication elements 300, 310. The communication element 300
Queue 301, congestion determination unit 302, congestion occurrence prediction unit 303, parameter observation unit 304, CCR observation unit 3
05, timeout detection unit 306, and ACR calculation unit 3
07, an inactivity determination threshold value calculation unit 308, a measurement period observation unit 309, an inactivity determination unit 311,
Congestion notification table 312 and EFCI bit setting unit 31
3 is included. The communication element 310 and the communication element 300 are connected by a communication path, and the terminals 320, 330, 34
0 are connected to the communication element 300 via a communication path. In this example, information is transferred in the form of a cell from a transmitting terminal accommodated in each of the terminals 320, 330, and 340 to a receiving terminal in the direction of the communication element 310 through the communication element 300. These cells are multiplexed in the queue 301 of the communication element 300 and output to the communication element 310. Although only one configuration for multiplexing is shown in this example, a similar configuration is required for each part where cells are multiplexed and congestion occurs.

Next, the operation of each part of the communication element 300 will be described. When a cell is input from a communication channel, the queue 301
Save the cell at the end of the queue. Also, queue 3
01 outputs the first cell among the stored cells to the EFCI bit setting unit 313 at a predetermined time interval. When receiving the cell, the queue 301 obtains the connection number CN from the contents of the VCI field and the VPI field of the cell, and outputs the value to the inactivity determining unit 311.

The congestion determining unit 302 determines whether the queue 301 is in a congested state by observing the number of cells stored in the queue 301 and the like. Then, when it is determined that the state is congested, a congestion determination signal is output to the EFCI bit setting unit 313, and when it is determined that the state is not congested, a non-congestion determination signal is transmitted to the EFCI bit setting unit 313. Output. In order for the congestion determining unit 302 to determine whether the queue 301 is in a congestion state, for example, the congestion determining unit 302 operates in the same manner as the queue length observing unit 103 and the congestion determining unit 104 shown in the first embodiment. What is necessary is just to comprise from the part which performs.

The congestion occurrence prediction unit 303 determines the number of cells stored in the queue 301 and the number of RMs arriving at the queue 301.
By observing the value of the CCR field of the cell, etc., it is predicted whether or not congestion will occur in the queue 301 in the future. If it is predicted that congestion will occur, the EFC
A congestion prediction signal is output to the I bit setting unit 313,
If it is predicted that no congestion will occur, a non-congestion prediction signal is output to EFCI bit setting section 313. In order to predict whether or not congestion will occur in the congestion occurrence prediction unit 303, for example, the congestion occurrence prediction unit 303 may be replaced by the parameter setting unit 202, the queue length observation unit 203, and the FRTT calculation shown in the second embodiment. Unit 205, CCR observation unit 20
6, timeout detection unit 207, ACR calculation unit 208,
What is necessary is just to comprise the part which functions similarly to the maximum input cell number prediction part 209, the congestion prediction threshold value calculation part 211, and the congestion occurrence prediction part 212. In this case, the congestion prediction flag Fp_cg can be set by the procedure shown in the flowchart of FIG.

Parameter observation section 304, CCR observation section 3
05, the timeout detection unit 306, and the ACR calculation unit 307 perform the same operations as the corresponding parts in the second embodiment.

The measurement period observation unit 309 outputs the measurement period end signal to the inactive determination unit 3 at a preset time interval.
11 is output.

Inactivity determination threshold value calculation section 308
Receives the ACR value and the connection number CN from the ACR calculation unit 307, adds a preset constant to the product of the received ACR value and the measurement period length Tm,
That is, by the following equation, the inactivity determination threshold T
Calculate h_na. Th_na = ACR × Tm + C The measurement period length Tm refers to a time interval at which the measurement period end signal is output from the measurement period observation unit 309.

Thereafter, the inactivity determination threshold value calculation unit 308 calculates the calculated inactivity threshold value Th_na
And outputs the received connection number CN to the inactivity determination unit 311.

The inactivity determination unit 311 determines the number of arriving cells and the inactivity determination threshold Th_na for each connection.
And the inactivity determination flag Fna. Upon receiving the connection number CN from the queue 301, the inactivity determination unit 311 increases the number of cells arriving at the corresponding connection by one. Then, the number of arriving cells of the connection is compared with the inactivity determination threshold Th_na. If the number of arriving cells is larger, the value of the inactivity determination flag Fna of the connection is set to "1". Further, upon receiving the inactivity determination threshold value Th_na and the connection number CN from the inactivity determination threshold value calculation unit 308, the inactivity determination unit 311 assigns the managed inactivity determination threshold value to the connection. Update Th_na to the received value. Then, the number of cells arriving at the connection and the inactivity determination threshold T
Compared with h_na, if the number of arriving cells is larger, the value of the inactivity determination flag Fna of the connection is set to “1”. Also, the inactivity determination unit 311
When receiving the measurement period end signal from the measurement period observation unit 309, the inactivity determination flag Fna of each connection
Is output to the congestion notification table 312, and the values of the inactivity determination flags Fna and the number of arrival cells of all connections are reset to “0”. However, the communication element 30
At the start of operation of 0, the value of the inactivity determination flag Fna and the value of the number of arrival cells are both set to “0”.

The congestion notification table 312 manages an inactivity determination flag Fna for each connection. The congestion notification table 312 indicates that the inactivity determination unit 3
11 to the inactivity judgment flag Fna of each connection.
When these values are received, those values are stored. The values of the inactivity determination flag Fna are all set to “0” when the operation of the communication element 300 starts.

The EFCI bit setting section 313 manages a congestion determination flag Fcg and a congestion prediction flag Fp_cg. E
The FCI bit setting section 313 sets the congestion determination flag Fcg to “1” when receiving the congestion determination signal from the congestion determination section 302, and sets the congestion determination flag Fcg to “0” when receiving the non-congestion determination signal from the congestion determination section 302. Set to. Also, E
The FCI bit setting unit 313 sets the congestion prediction flag Fp_cg to “1” when receiving the congestion prediction signal from the congestion occurrence prediction unit 303, and sets the congestion prediction flag Fp_cg to “1” when receiving the non-congestion prediction signal from the congestion generation prediction unit 303. Set to "0". However, when the operation of the communication element 300 is started, the values of the congestion determination flag Fcg and the congestion prediction flag Fp_cg are both set to “0”.

The EFCI bit setting section 313 stores the queue 3
01, a congestion determination flag Fcg
Is "1", the EFCI bit of the data cell is set to "1", and the data cell is output to the communication element 310. When both the values of the congestion determination flag Fcg and the congestion prediction flag Fp_cg are “0”, the data cell is output to the communication element 310 without changing the value of the EFCI bit of the data cell.

When the value of the congestion determination flag Fcg is “0”,
If the value of the congestion prediction flag Fp_cg is “1”, the EFC
The I-bit setting unit 313 calculates the connection number CN from the values of the VCI field and the VPI field of the data cell, and outputs the connection number CN to the congestion notification table 312. The congestion notification table 312 is
Connection number CN from EFCI bit setting section 313
Is received, the value of the inactivity determination flag Fna of the connection is referred to. If the value is "0", a congestion notification command signal is output to the EFCI bit setting unit 313, and the value is set to "1". If it is, a non-congestion notification command signal is output to the EFCI bit setting unit 313.
Upon receiving the non-congestion notification command signal, the EFCI bit setting unit 313 outputs the data cell to the communication element 310 without changing the value of the EFCI bit of the data cell.
On the other hand, when receiving the congestion notification command signal,
After setting the value of the FCI bit to “1”, the data cell is output to the communication element 310.

As described above, in the present embodiment, when the number of arriving cells for a certain connection is smaller than the inactivity determination threshold value Th_nc, that is, when the inactivity determination flag Fna is “0”, congestion occurs. If the congestion prediction flag Fp_cg is "1" even if the judgment flag Fcg is "0", the EFCI bit of the data cell transmitted in the connection is set to "1", so that the ACR of the ACR is transmitted to the transmitting terminal. A value reduction is indicated. In other words, according to the present embodiment, the number of input cells of each connection is observed, and if the value is much smaller than the number of cells calculated from the ACR value, the connection will be considered when congestion is predicted to occur. Is instructed to reduce the value of ACR. This can prevent the input rate from the transmitting terminal to the communication network from increasing rapidly. Therefore, according to the present embodiment, even when connections that generate data having a large burst property are multiplexed, it is possible to reduce the possibility that a cell loss occurs due to a sudden increase in the input rate.

In the above, when the occurrence of congestion is predicted, the EF of the data cell is set for a specific connection.
Although the embodiment in which the congestion notification is performed using the CI bit has been described, the CI (Congest
ion Indication) bit or ER (Explicit Cell Rat
e) An embodiment in which congestion notification is performed using a field or an embodiment in which an RM cell is generated in a communication element and congestion notification is performed using a CI bit or an ER field of the RM cell is also conceivable. Particularly, in an embodiment in which an RM cell is generated in a communication element and congestion notification is performed using the CI bit or the ER field of the RM cell, the ACR can be quickly reduced for a connection having a low input rate. It is more effective to prevent the rate spike and reduce the possibility of cell loss.

In the above embodiment, when the congestion determination flag Fcg is “0” and the congestion prediction flag Fp_cg is “1”, the data cell transmitted by the connection whose inactivity determination flag Fna is “0” is determined. Setting the EFCI bit to “1” instructs the transmitting terminal to reduce the ACR. Instead, the congestion determination flag F
When cg is “0” and the congestion prediction flag Fp_cg is “1”,
In order to prevent an abrupt increase in the input rate, by setting the NI bit of the RM cell to "1" for the connection for which the inactivity determination flag Fna is "0", the increase of the ACR to the transmitting terminal is prevented. Prohibition may be instructed.

<Fourth Embodiment> Next, a flow control method according to a fourth embodiment of the present invention will be described. FIG.
FIG. 11 is a block diagram showing a configuration of an ATM communication network including a communication element that executes a flow control method according to a fourth embodiment of the present invention. This communication network includes terminals 420, 430, 44
0 and communication elements 400 and 410. The communication element 400 includes a queue 401, a congestion determination unit 402, a congestion occurrence prediction unit 403, an inactivity determination unit 404,
A measurement period observation unit 405, a congestion notification table 406,
And an EFCI bit setting unit 407. Communication element 410
And the communication element 400 are connected by a communication path, and
The terminals 420, 430, and 440 are respectively connected to the communication element 4
00 is connected by a communication path. In this example, the terminal 42
Information is transferred in the form of cells from the transmitting terminal accommodated in each of 0, 430, and 440 to the receiving terminal in the direction of the communication element 410 through the communication element 400. These cells are multiplexed in the queue 401 of the communication element 400 and output to the communication element 410. Although only one configuration for multiplexing is shown in this example, a similar configuration is required for each part where cells are multiplexed and congestion occurs.

Next, the operation of each part of the communication element 400 will be described. The queue 401, the congestion determination unit 402, and the congestion occurrence prediction unit 403 perform the same operations as the corresponding parts in the third embodiment.

The measurement period observation unit 405 outputs the measurement period end signal to the inactive determination unit 4 at a predetermined time interval.
04 is output.

The inactivity determining unit 404 determines the number of arriving cells and the inactivity determination threshold Th_na for each connection.
And the inactivity determination flag Fna. When receiving the connection number CN from the queue 401, the inactivity determination unit 404 increases the number of cells arriving at the corresponding connection by one. Then, the number of arriving cells of the connection is compared with the inactivity determination threshold Th_na. If the number of arriving cells is larger, the value of the inactivity determination flag Fna of the connection is set to "1". However, the inactivity determination threshold value Th_na is set in advance for each connection. Further, the inactivity determination unit 404 includes the measurement period observation unit 40
When the measurement period end signal is received from No. 5, the value of the inactivity determination flag Fna of each connection is output to the congestion notification table 406, and the values of the inactivity determination flag Fna and the number of arrival cells of all connections are set to "0". Reset. However, when the operation of the communication element 400 is started, the value of the inactivity determination flag Fna and the value of the number of arrival cells are both set to “0”.

The congestion notification table 406 and the EFCI bit setting section 407 perform the same operations as the corresponding portions in the third embodiment. Therefore, in the present embodiment, as in the third embodiment, the number of cells arriving for a certain connection is determined by the inactivity determination threshold Th_.
nc, that is, the inactivity determination flag F
If na is “0”, the congestion prediction flag Fp_cg is “1” even if the congestion determination flag Fcg is “0”.
Setting the I bit to “1” instructs the transmitting terminal to reduce the ACR value.

As described above, according to this embodiment, as in the third embodiment, the number of input cells of each connection is observed, and if the value is very small, occurrence of congestion is predicted. Sometimes the ACR for that connection decreases. This can prevent the input rate from the transmitting terminal to the communication network from increasing rapidly. Therefore, according to the present embodiment, even when the present invention is applied to multiplexing of connections that generate data having a large burst property, it is possible to reduce the possibility of cell loss due to a sudden increase in the input rate. However, the inactivity determination threshold Th_na is
Since each connection is set in advance, the degree of the effect of the present embodiment is smaller than that of the third embodiment. However, this embodiment has an advantage that the configuration of the communication element is simpler than that of the third embodiment.

In the above description, when the occurrence of congestion is predicted, the EF of the data cell is transmitted to a specific connection.
Although the embodiment for performing the congestion notification using the CI bit has been described, the embodiment for performing the congestion notification using the CI bit or the ER field of the RM cell arriving at the communication element, and generating the RM cell in the communication element, An embodiment in which congestion notification is performed using the CI bit or the ER field of the RM cell is also conceivable. RM especially in communication elements
In an embodiment for generating a cell and performing congestion notification using the CI bit or ER field of the RM cell,
Since the ACR can be rapidly reduced for a connection with a low input rate, it is more effective to prevent a sudden increase in the input rate and reduce the possibility of cell loss.

Further, in the above embodiment, when the congestion determination flag Fcg is “0” and the congestion prediction flag Fp_cg is “1”, the data cell transmitted by the connection whose inactivity determination flag Fna is “0” is determined. By setting the EFCI bit to “1”, the transmitting terminal is instructed to reduce the ACR, but instead, the congestion determination flag F
When cg is “0” and the congestion prediction flag Fp_cg is “1”,
In order to prevent an abrupt increase in the input rate, by setting the NI bit of the RM cell to "1" for the connection for which the inactivity determination flag Fna is "0", the increase of the ACR to the transmitting terminal is prevented. Prohibition may be instructed.

<Fifth Embodiment> Next, a flow control method according to a fifth embodiment of the present invention will be described. FIG.
FIG. 2 is a block diagram illustrating a configuration of a communication element that executes a flow control method according to the embodiment. This communication network includes terminals 520, 530, 540 and communication elements 500, 510. The communication element 500 includes a queue 501, a congestion determination unit 502, a parameter observation unit 503, a CCR
Observation unit 504, timeout detection unit 505, ACR
Calculation unit 506, measurement period observation unit 507, active connection observation unit 508, and fair allocation calculation unit 50
9, a congestion notification table 511, and an EFCI bit setting unit 513. Communication element 510 and communication element 500
Are connected by a communication path, and the terminals 520, 53
0,540 is connected to the communication element 500 via a communication path. In this example, information is transferred in the form of a cell from the transmitting terminal accommodated in each of the terminals 520, 530, and 540 to the receiving terminal in the direction of the communication element 510 through the communication element 500. These cells are multiplexed in the queue 501 in the communication element 500 and output to the communication element 510. Although only one configuration for multiplexing is shown in this example, a similar configuration is required for each part where cells are multiplexed and congestion occurs.

Next, the operation of each part of the communication element 500 will be described. Congestion determination unit 502, parameter observation unit 503, CC
R observation unit 504, timeout detection unit 505, and A
The CR calculation unit 506 performs the same operation as the corresponding part in the second embodiment. Also, the queue 50
1, and the measurement period observation unit 507 performs the same operation as the corresponding part in the third embodiment.

The active connection observing section 508
It manages the number of cells arriving, the threshold Th_ac for active determination and the flag Fac for active determination for each connection.
The active connection observation unit 508 includes a queue 501
When the connection number CN is received from, the number of arrival cells of the corresponding connection is increased by one. Then, the number of arriving cells of the connection and the active determination threshold T
If the number of arrival cells is larger than h_ac, the value of the active determination flag Fac of the connection is set to “1”. However, the active determination threshold T
h_ac is set in advance for each connection. Also, the active connection observation unit 508
Receives the measurement period end signal from the measurement period observation unit 507, sums up the values of the active determination flags Fac of the respective connections, outputs the number as the number of active connections to the fair allocation calculation unit 509, and The values of the active determination flag Fac and the number of arrival cells are reset to “0”. However, when the operation of the communication element 500 is started, the value of the active determination flag Fac and the value of the number of arrival cells are both set to “0”.

When receiving the number of active connections from the active connection observing section 508, the fair allocation calculating section 509 divides the output bandwidth of the queue 501 by the number of active connections to obtain the fair allocation value Alc_e.
Calculate qu. Then, the value is stored in the congestion notification table 51.
Output for 1

The congestion notification table 511 manages the fair allocation value Alc_equ and the congestion notification flag Fcgnf of each connection. Upon receiving the fair allocation value Alc_equ from the fair allocation calculation unit 509, the congestion notification table 511 updates the managed fair allocation value Alc_equ to the received value. In addition, the congestion notification table 511 includes A
ACR value and connection number CN from CR calculation section 506
Is received, the received ACR value is compared with the fair allocation value Alc_equ. Based on the result of the comparison, the congestion notification table 511 indicates that the value of the ACR is equal to the fair allocation value Alc.
If the value is larger than _equ, the value of the congestion notification flag Fcgnf of the connection is set to “1”, and if the value of the ACR is smaller than the fair allocation value Alc_equ, the value of the congestion notification flag Fcgnf of the connection is changed. Set to “0”. However, the values of the fair allocation value Alc_equ and the congestion notification flag Fcgnf are all set to “0” at the start of operation of the communication element 500.

The EFCI bit setting section 513 manages the congestion determination flag Fcg. EFCI bit setting unit 51
3 receives the congestion determination signal from the congestion determination unit 502, sets the congestion determination flag Fcg to “1”, and sets the congestion determination unit 50
When the non-congestion determination signal is received from 2, the congestion determination flag Fcg
Is set to “0”. However, when the operation of the communication element 500 starts, the value of the congestion determination flag Fcg is set to “0”.

The EFCI bit setting unit 513 stores the queue 5
01, a congestion determination flag Fcg
Is “0”, the data cell is output to the communication element 510 without changing the value of the EFCI bit of the data cell. When the value of the congestion determination flag Fcg is “1”, the connection number CN is calculated from the values of the VCI field and the VPI field of the data cell, and the connection number CN is output to the congestion notification table 511. Upon receiving the connection number CN from the EFCI bit setting unit 513, the congestion notification table 511 refers to the value of the congestion notification flag Fcgnf of the connection.
The non-congestion notification command signal is output to the bit setting unit 513, and if it is “0”, the EFCI bit setting unit 513
Output to When receiving the non-congestion notification command signal, the EFCI bit setting unit 513
Without changing the value of the bit, the data cell is
Output to. On the other hand, when the congestion notification command signal is received, the value of the EFCI bit of the data cell is set to “1”, and the data cell is output to the communication element 510.

As described above, in the present embodiment, when the congestion determination flag Fcg is “1”, the congestion notification flag Fcgnf for the connection corresponding to the data cell received by the communication element 500 is “1”. At this time, the EFCI bit of the data cell is set to "1", thereby instructing the transmitting terminal to reduce the ACR value. That is, in the present embodiment, the ACR value of each connection is observed, and congestion notification is performed only for connections whose ACR value is greater than the fair allocation value Alc_equ. Therefore, according to the present embodiment, even in a communication network in which many communication elements are connected, the congestion notification is not concentrated on the connections passing through many communication elements, so that the connection between the connections related to the usage rate of the transmission band is not increased. Injustice is reduced.

In the above, an embodiment has been described in which congestion notification is performed using a EFCI bit of a data cell for a specific connection, but a CI bit or an ER field of an RM cell arriving at a communication element is used. An embodiment in which a congestion notification is performed by using an RM cell in a communication element and a congestion notification is performed using the CI bit or the ER field of the RM cell is also conceivable. In addition, at the time of congestion, for the connection in which the congestion notification flag Fcgnf is “1”, the input bit rate is instructed by setting the CI bit of the RM cell, and the connection in which the congestion notification flag Fcgnf is “0” is set. On the other hand, an embodiment in which increase of the input rate is prohibited by setting the NI bit of the RM cell is also conceivable.

In addition to the above operations, when the number of cells stored in the queue is very large and the congestion state of the communication element is serious, a congestion notification is made for all connections, thereby An embodiment is also conceivable in which the unfairness between the connections regarding the usage rate of the transmission band is reduced, and the cell loss in the communication element is reduced.

Furthermore, in the above-described embodiment, a congestion occurrence prediction unit is provided and a congestion prediction flag Fp_cg is introduced, as in the third embodiment, and the congestion determination flag Fcg is “0” and the congestion prediction flag Fp_cg is “ At the time of “1”, the NI bit of the RM cell is set to “1” for the connection for which the congestion notification flag Fcgnf is “1” in order to prevent a sudden increase in the input rate, thereby preventing the transmission terminal from transmitting. Alternatively, an instruction to prohibit an increase in the ACR may be issued.

<Sixth Embodiment> Next, a flow control method according to a sixth embodiment of the present invention will be described. FIG.
FIG. 1 is a block diagram illustrating a configuration of an ATM communication network including a communication element that executes a flow control method according to an embodiment.
This communication network includes terminals 620, 630, and 640 and communication elements 600 and 610. The communication element 600
A queue 601, a congestion determination unit 602, a parameter observation unit 603, a CCR observation unit 604, a timeout detection unit 605, an ACR calculation unit 606, an ABR connection number calculation unit 607, a fair allocation calculation unit 608, Notification table 609 and EFCI bit setting section 611
And The communication element 610 and the communication element 600 are connected by a communication path, and the terminals 620, 630, and 640
Are connected to the communication element 600 via communication paths. In this example, information is transferred in the form of a cell from the transmitting terminal accommodated in each of the terminals 620, 630, and 640 to the receiving terminal in the direction of the communication element 610 through the communication element 600. These cells are multiplexed in the queue 601 in the communication element 600 and output to the communication element 610. Although only one configuration for multiplexing is shown in this example, a similar configuration is required for each part where cells are multiplexed and congestion occurs.

Next, the operation of each part of the communication element 600 will be described. Queue 601, congestion determination unit 602, parameter observation unit 603, CCR observation unit 604, timeout detection unit 6
05, ACR calculation unit 606, congestion notification table 609,
The EFCI bit setting unit 611 performs the same operation as the corresponding part in the fifth embodiment.

The ABR connection number calculation unit 607 manages the number of ABR connections, which is the number of ABR service connections set on the queue 601.
The ABR connection number calculation unit 607 observes cells arriving at the queue 601 and, if a signaling cell indicating a connection setting arrives, increases the number of ABR connections by 1 and thereafter calculates the number of ABR connections fairly allocated Output to the unit 608. Conversely, when a signaling cell indicating connection deletion arrives, the number of ABR connections is reduced by 1 and thereafter the number of ABR connections is calculated by the fair allocation calculation unit 608.
Output to However, at the start of operation of the communication element 600, the number of ABR connections is set to “0”.

[0185] The fair allocation calculation unit 608
1 manages the queue output band, which is the speed at which cells are output. When receiving the number of ABR connections from the number of ABR connections calculation unit 607, the fair allocation calculation unit 608 calculates the fair allocation value Alc_equ by dividing the output bandwidth of the queue 601 by the number of ABR connections. Then, the value is output to the congestion notification table 609.

As described above, in the present embodiment, AB
The fifth embodiment differs from the fifth embodiment in which the fair allocation value Alc_equ is calculated using the number of active connections in that the fair allocation value Alc_equ is calculated using the number of R connections. Comparative fair allocation value A
Calculation of lc_equ is simplified. On the other hand, this embodiment is the same as the fifth embodiment in that the EFCI bit in the data cell is set according to the value of the congestion notification flag Fcgnf set based on the fair allocation value Alc_equ. Therefore, also in the present embodiment, the congestion determination flag Fcg
Is “1”, when the congestion notification flag Fcgnf for the connection corresponding to the data cell received by the communication element 600 is “1”, the EFCI bit of the data cell is set to “1”. Thus, the transmitting terminal is instructed to reduce the ACR value. That is, in the present embodiment, the value of the ACR of each connection is observed, and congestion notification is performed only for connections whose ACR value is greater than the fair allocation value Alc_equ. Therefore,
According to the present embodiment, even in a communication network in which many communication elements are connected, congestion notification is not concentrated on connections passing through many communication elements, and therefore, unfairness among connections regarding the usage rate of the transmission band. Is alleviated.

In the above, the embodiment in which congestion notification is performed using a EFCI bit of a data cell for a specific connection has been described.
An embodiment in which congestion notification is performed using the CI bit or the ER field of a cell or an embodiment in which an RM cell is generated in a communication element and congestion notification is performed using the CI bit or the ER field of the RM cell is also conceivable. In addition, at the time of congestion, for the connection for which the congestion notification flag Fcgnf is “1”, the CI bit of the RM cell is set to instruct the reduction of the input rate, and the congestion notification flag Fcgnf
Is "0" for the NI of the RM cell.
An embodiment in which an increase in the input rate is prohibited by setting a bit is also conceivable.

In addition to the above operation, when the number of cells stored in the queue is very large and the congestion state of the communication element is serious, a congestion notification is performed for all connections, thereby An embodiment in which the cell loss in the communication element is reduced while alleviating the inequality between the connections regarding the usage rate of the transmission band is also conceivable.

Further, in the above embodiment, a congestion occurrence prediction unit is provided and a congestion prediction flag Fp_cg is introduced as in the third embodiment, and the congestion judgment flag Fcg is "0" and the congestion prediction flag Fp_cg is " At the time of “1”, the NI bit of the RM cell is set to “1” for the connection for which the congestion notification flag Fcgnf is “1” in order to prevent a sudden increase in the input rate, thereby preventing the transmission terminal from transmitting. A prohibition of the increase of the ACR may be instructed.

<Seventh Embodiment> Next, a flow control method according to a seventh embodiment of the present invention will be described. FIG.
FIG. 1 is a block diagram illustrating a configuration of an ATM communication network including a communication element that executes a flow control method according to an embodiment.
This communication network includes terminals 720, 730, 740 and communication elements 700, 710. The communication element 700 includes a queue 701, a congestion determination unit 702, an active connection observation unit 703, a fair allocation calculation unit 704,
A measurement period observation unit 705, an input cell number calculation unit 706,
Input cell number comparing section 707 and EFCI bit setting section 70
8 and a congestion notification table 709. Communication element 71
0 and the communication element 700 are connected by a communication path, and the terminals 720, 730, and 740 are respectively connected to the communication element 700 by the communication path. In this example, information is transferred in the form of a cell from the transmitting terminal accommodated in each of the terminals 720, 730, and 740 to the receiving terminal in the direction of the communication element 710 through the communication element 700. Each of these cells is multiplexed in the queue 701 of the communication element 700,
Output to communication element 710. Although only one configuration for multiplexing is shown in this example, a similar configuration is required for each part where cells are multiplexed and congestion occurs.

Next, the operation of each section of the communication element 700 will be described. Congestion determination unit 702, active connection observation unit 703, fair allocation calculation unit 704, measurement period observation unit 7
05, the EFCI bit setting unit 708 performs the same operation as the corresponding part in the fifth embodiment.

The input cell number calculation section 706 manages the number of input cells for each connection. Input cell number calculation unit 7
06 receives the connection number CN from the queue 701, increases the number of input cells of the connection by 1, and outputs the connection number CN and the number of input cells to the congestion notification table 707. When receiving the measurement period end signal from the measurement period observation unit 705, the input cell number calculation unit 706 resets the number of input cells of all connections to “0”. When the operation of the communication element 700 is started, the number of input cells of all connections is set to “0”.

The input cell number comparison unit 707 calculates the input cell number threshold value Th_in and the congestion notification flag Fcgnf of each connection.
Is managing. Upon receiving the fair allocation value Alc_equ from the fair allocation calculation unit 704, the input cell number comparison unit 707 calculates the input cell number threshold value Th_in by multiplying the value by the measurement period length Tm, that is, by the following equation. . Th_in = Alc_equ × Tm Here, the measurement period length Tm is a time interval at which the measurement period observation unit 705 outputs a measurement period end signal. Upon receiving the input cell number and the connection number CN from the input cell number calculation section 706, the input cell number comparison section 707 compares the received input cell number with the input cell number threshold value Th_in. When the number of input cells is larger, the value of the congestion notification flag Fcgnf of the connection is set to “1”. When the input cell number threshold Th_in is larger, the congestion notification flag Fcgnf is set. Set to “0”. However, the values of the input cell number threshold Th_in and the congestion notification flag Fcgnf are:
At the start of operation of the communication element 700, all are set to "0". Upon receiving the measurement period end signal, the input cell number comparison unit 707 receives the congestion notification flags F for all connections.
The value of cgnf is output to the congestion notification table 709, and then the values of the congestion notification flags Fcgnf of all connections are reset to “0”.

The congestion notification table 709 manages the congestion notification flag Fcgnf for each connection. When the value of the congestion notification flag Fcgnf is received from the input cell number comparison unit 707, the value of the managed congestion notification flag Fcgnf is managed. Is updated to the received value. At the start of operation of the communication element 700, the values of the congestion notification flags Fcgnf are all set to "0".

As described above, in the present embodiment, the value of the congestion notification flag Fcgnf is set based on the comparison result between the input cell number threshold Th_in and the input cell number calculated using the fair allocation value Alc_equ. This is different from the fifth embodiment in which the value of the congestion notification flag Fcgnf is set based on the comparison result between the fair allocation threshold value Alc_equ and the value of ACR. However, in the present embodiment, the fair allocation value Alc_equ
Is the same as the fifth embodiment in that the EFCI bit in the data cell is set according to the value of the congestion notification flag Fcgnf set based on.

As described above, in the present embodiment, the number of input cells of each connection is observed, and congestion notification is performed only for connections whose value is larger than the number of cells calculated from the fair allocation value Alc_equ. Therefore, according to the present embodiment, even in a communication network in which many communication elements are connected,
Since congestion notification is not concentrated on connections passing through many communication elements, unfairness among connections regarding the usage rate of the transmission band is reduced.

In the above description, an embodiment has been described in which congestion notification is performed using the EFCI bit of a data cell for a specific connection, but the CI bit or ER field of an RM cell arriving at a communication element is used. An embodiment in which a congestion notification is performed by using an RM cell in a communication element and a congestion notification is performed using the CI bit or the ER field of the RM cell is also conceivable. Also, at the time of congestion, for the connection in which the congestion notification flag Fcgnf is “1”, the input bit rate is instructed by setting the CI bit of the RM cell, and the connection in which the congestion notification flag Fcgnf is “0” is set. On the other hand, an embodiment is also conceivable in which setting of the NI bit of the RM cell instructs prohibition of an increase in the input rate.

In addition to the above operation, when the number of cells stored in the queue is very large and the congestion state of the communication element is serious, a congestion notification is made for all connections, thereby An embodiment is also conceivable in which the unfairness between the connections regarding the usage rate of the transmission band is reduced, and the cell loss in the communication element is reduced.

Further, in the above-described embodiment, a congestion occurrence prediction unit is provided and a congestion prediction flag Fp_cg is introduced as in the third embodiment and the like. At the time of “1”, the NI bit of the RM cell is set to “1” for the connection for which the congestion notification flag Fcgnf is “1” in order to prevent a sudden increase in the input rate, thereby preventing the transmission terminal from transmitting. A prohibition of the increase of the ACR may be instructed.

<Eighth Embodiment> Next, a flow control method according to an eighth embodiment of the present invention will be described. FIG.
0 is a block diagram illustrating a configuration of an ATM communication network including communication elements that execute the flow control method according to the present embodiment. This communication network includes terminals 820, 830, 840 and communication elements 800, 810. Communication element 800
Is a queue 801, a congestion determination unit 802, an ABR connection number calculation unit 803, and a fair allocation calculation unit 804.
, Measurement period observation unit 805, input cell number calculation unit 806
, An input cell number comparison unit 807, an EFCI bit setting unit 808, and a congestion notification table 809. The communication element 810 and the communication element 800 are connected by a communication path,
The terminals 820, 830, and 840 are connected to the communication element 800 via communication paths. In this example, information is transferred in the form of a cell from the transmitting terminal accommodated in each of the terminals 820, 830, 840 to the receiving terminal in the direction of the communication element 810 through the communication element 800. These cells are multiplexed in the queue 801 of the communication element 800 and output to the communication element 810. In this example, only one configuration for multiplexing is shown,
A similar configuration is required for each part where cells are multiplexed and congestion occurs.

Next, the operation of each unit of the communication element 800 will be described. Queue 801, congestion determination unit 802, measurement period observation unit 805, input cell number calculation unit 806, input cell number comparison unit 8
07, the EFCI bit setting unit 808, and the congestion notification table 809 perform the same operations as the corresponding parts in the seventh embodiment.

[0202] The number of ABR connections calculation unit 803 manages the number of ABR connections, which is the number of ABR service connections set on the queue 801.
The ABR connection number calculation unit 803 observes a cell arriving at the queue 801, and when a signaling cell indicating a connection setting arrives, increases the number of ABR connections by 1 and thereafter calculates the number of ABR connections fairly allocated. Output to the unit 804. Conversely, when a signaling cell indicating connection deletion arrives, the number of ABR connections is reduced by 1 and thereafter the number of ABR connections is calculated by the fair allocation calculation unit 804.
Output to However, when the operation of the communication element 800 is started, the number of ABR connections is set to “0”.

The fair allocation calculation unit 804
1 manages the queue output band, which is the speed at which cells are output. When receiving the number of ABR connections from the ABR connection number calculation unit 803, the fair allocation calculation unit 804 calculates a fair allocation value Alc_equ by dividing the queue output bandwidth by the number of ABR connections (fair allocation value = queue output bandwidth / ABR connection). number). Then, the value is output to the congestion notification table 809.

As described above, in the present embodiment, AB
The seventh embodiment differs from the seventh embodiment in which the fair allocation value is calculated using the number of active connections in that the fair allocation value is calculated using the number of R connections. However, the present embodiment is different from the seventh embodiment in that the value of the congestion notification flag Fcgnf is set based on the comparison result between the input cell number and the input cell number threshold value Th_in calculated using the fair allocation value Alc_equ.
This is the same as the embodiment.

As described above, in the present embodiment, the number of input cells of each connection is observed, and congestion notification is performed only for connections whose value is larger than the number of cells calculated from the fair allocation value Alc_equ. Therefore, according to the present embodiment, even in a communication network in which many communication elements are connected, the congestion notification is not concentrated on the connections passing through many communication elements, so that the connection between the connections related to the usage rate of the transmission band is not increased. Injustice is reduced.

In the above description, an embodiment has been described in which congestion notification is performed using the EFCI bit of a data cell for a specific connection, but the CI bit or ER field of an RM cell arriving at a communication element is used. An embodiment in which a congestion notification is performed by using an RM cell in a communication element and a congestion notification is performed using the CI bit or the ER field of the RM cell is also conceivable. Also, at the time of congestion, for the connection in which the congestion notification flag Fcgnf is “1”, the input bit rate is instructed by setting the CI bit of the RM cell, and the connection in which the congestion notification flag Fcgnf is “0” is set. On the other hand, an embodiment in which an increase in the input rate is prohibited by setting the NI bit of the RM cell is also conceivable.

In addition to the above operation, when the number of cells stored in the queue is very large and the congestion state of the communication element is serious, a congestion notification is performed for all the connections. An embodiment is also conceivable in which the unfairness between the connections regarding the usage rate of the transmission band is reduced, and the cell loss in the communication element is reduced.

Further, in the above embodiment, a congestion occurrence prediction unit is provided and a congestion prediction flag Fp_cg is introduced as in the third embodiment, and the congestion determination flag Fcg is “0” and the congestion prediction flag Fp_cg is “1”. At the time of “1”, the NI bit of the RM cell is set to “1” for the connection for which the congestion notification flag Fcgnf is “1” in order to prevent a sudden increase in the input rate, thereby preventing the transmission terminal from transmitting. A prohibition of the increase of the ACR may be instructed.

<Ninth Embodiment> Next, a flow control method according to a ninth embodiment of the present invention will be described. FIG.
FIG. 1 is a block diagram illustrating a configuration of an ATM communication network including a communication element that executes a flow control method according to the present embodiment. This communication network includes terminals 920, 930, 940 and communication elements 900, 910. Communication element 900
Are a queue 901, a congestion determination unit 902, a parameter observation unit 903, a CCR observation unit 904, a timeout detection unit 9
05, ACR calculation unit 906, measurement period observation unit 907, A
CR maximum value calculator 908, ACR threshold calculator 90
9, ACR comparing section 911, congestion notification table 912, E
An FCI bit setting unit 913 is included. The communication element 910 and the communication element 900 are connected by a communication path, and the terminals 920, 930, and 940 are connected to the communication element 900, respectively.
Are connected by a communication path. In this example, terminals 920,
From the transmitting terminals accommodated in each of 930 and 940,
Information is transferred in the form of cells through communication element 900 to a receiving terminal in the direction of communication element 910. Each of these cells
The data is multiplexed in the queue 901 of the communication element 900 and output to the communication element 910. Although only one configuration for multiplexing is shown in this example, a similar configuration is required for each part where cells are multiplexed and congestion occurs.

Next, the operation of each part of the communication element 900 will be described. Queue 901, congestion determination unit 902, parameter observation unit 903, CCR observation unit 904, timeout detection unit 9
05, the measurement period observation unit 907 performs the same operation as the corresponding part in the third embodiment.

[0211] The ACR calculation unit 906 calculates the connection number C of each connection using the ABR service.
The ACR value and the ICR value are managed corresponding to N. A
Upon receiving the values of the connection number CN and the ICR from the parameter observation unit 903, the CR calculation unit 906 newly secures a storage area for managing the ICR and the ACR corresponding to the received connection number CN, and A
The value of CR is set to the value of ICR received together. Further, upon receiving the connection number CN and the CCR value from the CCR observation unit 904, the ACR calculation unit 906 updates the ACR value corresponding to the received connection number CN with the received CCR value. Further, the ACR calculation unit 906
Is the connection number C from the timeout detection unit 905.
When N is received, the ACR value corresponding to the received connection number CN is updated to the ICR value of the connection. The ACR calculation unit 906 includes a measurement period observation unit 907
When the measurement period end signal is received from, the ACR value of each connection is output to the ACR maximum value calculation unit 908.

[0212] The ACR maximum value calculation unit 908 manages the ACR maximum value. The ACR maximum value calculation unit 908 calculates
When the ACR value of each connection is received from the R calculation unit 906, the received ACR value is compared with the ACR maximum value. If the received ACR value is larger, the ACR maximum value is updated to the received ACR value.
However, when the operation of the communication element 900 is started, the ACR maximum value is set to “0”. ACR maximum value calculator 9
In step 08, the largest value among the received ACR values is obtained by the above operation. Then, the ACR maximum value finally obtained is output to the ACR threshold value calculation unit 909, and the managed ACR maximum value is reset to “0”.

Upon receiving the ACR maximum value from the ACR maximum value calculation unit 908, the ACR threshold value calculation unit 909 calculates an ACR threshold value Th_ACR by subtracting a predetermined constant from the received ACR maximum value, The value is output to the ACR comparing section 911 (ACR threshold = ACR maximum-constant). However, the ACR threshold Th
It is assumed that the value of the above constant has been adjusted so that the value of _ACR is close to the ACR maximum value.

[0214] The ACR comparing section 911 calculates the ACR threshold T
h_ACR and a congestion notification flag Fcgnf of each connection are managed. The ACR comparison unit 911 calculates the ACR threshold Th
Upon receiving _ACR, the managing ACR threshold Th_A
Update CR to the received value. After that, an ACR output command signal is output to the ACR calculation unit 906. A
Upon receiving the ACR output command signal, the CR calculation unit 906 outputs the ACR value of each managed connection to the ACR comparison unit 911. The ACR comparison unit 911
When the ACR value of each connection is received from the ACR calculation unit 906, the received ACR value and the ACR threshold Th_A
Compare with CR. Based on the result of this comparison, the ACR comparing unit 911 determines, for a connection whose ACR value is larger than the ACR threshold Th_ACR, the congestion notification flag F
The value of cgnf is set to “1”, and the value of the congestion notification flag Fcgnf is set to “0” for a connection whose ACR value is smaller than the ACR threshold Th_ACR. And
The ACR comparing unit 911 receives the ACR values of all the connections, and sets the congestion notification flags F of all the connections.
When the value of cgnf is set, the value of the congestion notification flag Fcgnf of each connection is output to the congestion notification table 912.

[0215] The EFCI bit setting section 913 manages the congestion determination flag Fcg. EFCI bit setting section 91
3 receives the congestion determination signal from the congestion determination unit 902, sets the congestion determination flag Fcg to “1”, and sets the congestion determination unit 90
When the non-congestion determination signal is received from the control unit 2, the congestion determination flag Fcg
Is set to “0”. However, when the operation of the communication element 900 is started, the value of the congestion determination flag Fcg is set to “0”.

The congestion notification table 912 manages a congestion notification flag Fcgnf for each connection. Upon receiving the congestion notification flag Fcgnf of each connection from the ACR comparing unit 911, the congestion notification table 912 updates the value of the managed congestion notification flag Fcgnf to the received value.
Note that the value of the congestion notification flag Fcgnf is all set to “0” when the operation of the communication element 900 starts.

The EFCI bit setting section 913 sets the queue 9
01, a congestion determination flag Fcg
Is “0”, the data cell is output to the communication element 910 without changing the value of the EFCI bit of the data cell. When the value of the congestion determination flag Fcg is “1”, the EFCI bit setting unit 913 calculates the connection number CN from the values of the VCI field and the VPI field of the data cell, and stores the connection number CN in the congestion notification table 912. Output to Upon receiving the connection number CN from the EFCI bit setting unit 913, the congestion notification table 912 refers to the value of the congestion notification flag Fcgnf of the connection, and if the value is “1”, transmits the congestion notification command signal to the EFCI bit. Setting unit 91
3 and outputs a non-congestion notification command signal to the EFCI bit setting unit 913 when the signal is “0”. When receiving the non-congestion notification command signal, the EFCI bit setting unit 913 outputs the data cell to the communication element 910 without changing the value of the EFCI bit of the data cell. On the other hand, when receiving the congestion notification command signal, the EFCI bit setting unit 913 sets the value of the EFCI bit of the data cell to “1”, and then outputs the data cell to the communication element 910.

As described above, in the flow control according to the present embodiment, the ACR value for each connection is calculated, and the congestion notification flag Fcgnf for each connection is set using the ACR value. The EFCI bit in the data cell is set based on the congestion notification flag Fcgnf in addition to the congestion determination flag Fcg. Therefore, in the following, the ACR for each connection
A procedure for calculating the value (hereinafter referred to as “ACR calculation procedure”) and a procedure for setting the value of the congestion notification flag Fcgnf (hereinafter referred to as “congestion notification flag setting procedure”) will be described.

FIG. 12 is a flowchart showing the ACR calculation procedure in the present embodiment. In this flowchart, ACR [CN] represents the value of ACR for the connection with connection number CN, and the timer value [C
N] represents the timer value of the timer corresponding to the connection of connection number CN, ICR [CN] represents the value of ICR for the connection of connection number CN, and ADTF [CN] represents the value of ADTF for the connection of connection number CN. Shall be represented.

As shown in FIG. 12, the ACR calculation procedure is as follows.
Fired when any of cell arrival and timeout events occur.

First, the case where the ACR calculation procedure is activated upon arrival of a cell will be described. When a cell arrives at the queue 901 (step S900), the queue 901 outputs a queue length increase signal. The congestion determination unit 902 according to the present embodiment is configured by a portion that functions similarly to the queue length observation unit 103 and the congestion determination unit 104 according to the first embodiment, and a queue length increase signal is output from the queue 901. Then, the queue length L_que is increased by 1 (step S902). Note that the queue length L_que is set to “0” when the operation of the communication element 900 starts.
When a cell is output from the queue 901, the queue 9
From 01, a queue length decrease signal is output to the congestion determination unit 902, and the congestion determination unit 902 reduces the queue length L_que by 1 (not shown).

After that, the type of the cell arriving at the queue 901 is determined by the parameter observation unit 903 and the CCR observation unit 90.
4 (Step S90)
4). As a result, if the cell is a signaling cell for setting up an ABR service connection, the following processing is performed. That is, the parameter observation unit 903
, The ICR value of the connection and the connection number CN are detected from the cell, and the ACR calculation unit 90
6, the ACR value for the connection is I
It is set to the value of CR (step S906). When the ACR value is set for the connection corresponding to the above-mentioned signaling cell arriving at the queue 901, the ACR calculation procedure ends.

The type of the cell arriving at the queue 901 is determined by the CCR observation unit 904 (step S90).
4, S912), as a result, if the cell is an RM cell, the CCR observation unit 904 obtains a CCR value from the RM cell and calculates a connection number CN corresponding to the RM cell (step S912). S924).
This connection number CN is a timeout detection unit 905
Is output to Further, the CCR value and the connection number CN are output to the ACR calculation unit 906, and the ACR calculation unit 9
At 06, the value of the ACR for the connection is
The value is set to the CR value (step S926). When the connection number CN is output to the timeout detection unit 905, the timer corresponding to the connection number CN starts after its timer value is initialized to “0” (step S928). In this way, the ACR value is set for the connection corresponding to the RM cell arriving at the queue 901, and when the timer starts, the ACR calculation procedure ends.

If it is determined that the cell arriving at the queue 901 is neither a signaling cell nor an RM cell (step S912), the ACR calculation unit 906 does not change the held ACR value, and The ACR calculation procedure ends without setting a new ACR value.

Next, a case where the ACR calculation procedure is started due to a timeout will be described. Step S described above
At 928, after the timer corresponding to a certain connection has its timer value initialized to “0” and started, if the elapsed time from the start time, that is, the timer value, becomes equal to the ADTF value of the connection (S930). , The connection number C of the connection
N is the timeout detection unit 905 to the ACR calculation unit 906
Is output to When the connection number CN is received by the ACR calculation unit 906, the ACR value corresponding to the connection number CN is the ICR of the connection.
(Step S932).

When the ACR value for the connection corresponding to the timeout is set to the ICR value in this way, the ACR calculation procedure ends.

FIG. 13 is a flowchart showing a procedure for setting a congestion notification flag in this embodiment. In this flowchart, ACR [CN] represents the value of the ACR for the connection with the connection number CN, and Fcgnf
[CN] represents the value of the congestion notification flag for the connection with the connection number CN. In this congestion notification flag setting procedure, using the ACR value of each connection calculated by the above ACR calculation procedure, a congestion notification flag Fcg is set for each connection as follows.
nf is set.

This congestion notification flag setting procedure is started by a measurement period end signal. That is, when the measurement end signal is output from the measurement period observation unit 907 to the ACR calculation unit 906 at a preset time interval, and the measurement end signal is output, the ACR value of each connection is changed to the ACR maximum value calculation unit 908. Is output to ACR maximum value calculation unit 908
Then, the maximum value of these ACR values is calculated (step S952), and the maximum value is output to the ACR threshold value calculation unit 909 as the ACR maximum value.

When the ACR maximum value is output from the ACR maximum value calculation unit 908, the ACR threshold value calculation unit 909 subtracts a predetermined constant from the ACR maximum value to calculate the ACR threshold value Th_ACR. Is performed (step S954). This ACR threshold Th_ACR
Is output to the ACR comparing section 911.

When the ACR threshold Th_ACR is output from the ACR threshold calculator 909, an ACR output command signal is output from the ACR comparator 911 to the ACR calculator 906. In response to this ACR output command signal, the ACR
The calculation unit 906 outputs the ACR value of each connection to the ACR comparison unit 911. The ACR comparing section 911 compares the ACR value of each connection output from the ACR calculating section 906 with the ACR threshold Th_ACR output from the ACR threshold calculating section 909 (step S958). As a result of the comparison, for the connection whose ACR value is larger than the ACR threshold Th_ACR, the congestion notification flag Fcgnf [CN] is set to “1” (step S960), and the ACR value is set to the ACR threshold Th_ACR.
For the following connections, the congestion notification flag Fcgnf is set to “0” (step S962).

As described above, when the comparison in step S958 is performed for all connections and the congestion notification flags Fcgnf are set for all connections, the congestion notification flag setting procedure ends (step S9).
56).

In this embodiment, when the congestion determination flag Fcg is “1” and the congestion notification flag Fcgnf for the connection corresponding to the data cell received by the communication element 900 is “1”, the data cell Is set to “1”, thereby instructing the transmitting terminal to reduce the ACR value. The value of the congestion notification flag Fcgnf used at this time is set based on a comparison between the ACR threshold value Th_ACR set to a value close to the ACR maximum value and the ACR value of each connection. That is, in the present embodiment, the ACR value of each connection is observed, and congestion notification is performed only for connections whose values are close to the maximum value. Therefore, according to the present embodiment, even in a communication network in which many communication elements are connected, the congestion notification is not concentrated on the connections passing through many communication elements, so that the connection between the connections related to the usage rate of the transmission band is not increased. Injustice is reduced.

In the above description, the embodiment in which congestion notification is performed using the EFCI bit of the data cell for a specific connection has been described, but the CI bit or ER field of the RM cell arriving at the communication element is used. An embodiment in which a congestion notification is performed by using an RM cell in a communication element and a congestion notification is performed using the CI bit or the ER field of the RM cell is also conceivable. Also, at the time of congestion, for the connection in which the congestion notification flag Fcgnf is “1”, the input bit rate is instructed by setting the CI bit of the RM cell, and the connection in which the congestion notification flag Fcgnf is “0” is set. On the other hand, an embodiment in which an increase in the input rate is prohibited by setting the NI bit of the RM cell is also conceivable.

In addition to the above operations, when the number of cells stored in the queue is very large and the congestion state of the communication element is serious, a congestion notification is made for all connections, thereby An embodiment in which the cell loss in the communication element is reduced while alleviating the inequality between the connections regarding the usage rate of the transmission band is also conceivable.

Further, in the above-described embodiment, a congestion occurrence prediction unit is provided and a congestion prediction flag Fp_cg is introduced as in the third embodiment and the like. At the time of “1”, the NI terminal of the RM cell is set to “1” for the connection in which the congestion notification flag Fcgnf is “1” in order to prevent a sudden increase in the input rate, thereby preventing the transmission terminal from transmitting. Alternatively, an instruction to prohibit an increase in the ACR may be issued.

<Tenth Embodiment> Next, a tenth embodiment of the present invention will be described.
The flow control method according to the embodiment 0 will be described.
FIG. 14 is a block diagram illustrating a configuration of an ATM communication network including communication elements that execute the flow control method according to the present embodiment. This communication network includes terminals 1020, 1030, 104
0, and communication elements 1000 and 1010. The communication element 1000 includes a queue 1001 and a congestion determination unit 10.
02, input cell number calculation section 1003, measurement period observation section 1004, input cell number maximum value calculation section 1005, input cell number threshold value calculation section 1006, input cell number comparison section 1
007, a congestion notification table 1008, and an EFCI bit setting unit 1009. The communication element 1010 and the communication element 1000 are connected by a communication path.
020, 1030, and 1040 are communication elements 1 respectively.
000 via a communication path. In this example, terminal 1
020, 1030, and 1040, the communication element 101 through the communication element 1000
The information is transferred in the form of a cell to the receiving terminal in the 0 direction. Each of these cells is a queue 1001 of the communication element 1000.
And output to the communication element 1010.
Although only one configuration for multiplexing is shown in this example, a similar configuration is required for each part where cells are multiplexed and congestion occurs.

Next, the operation of each unit of the communication element 1000 will be described. The queue 1001, the congestion determination unit 1002, and the measurement period observation unit 1004 perform the same operations as the corresponding parts in the third embodiment.

The input cell number calculation unit 1003 manages the number of input cells for each connection using the ABR service. The input cell number calculation unit 1003
When receiving the connection number CN from 01, the input cell number of the connection is increased by one. Then, when receiving the measurement period end signal from the measurement period observation unit 1004, it outputs the number of input cells of each managed connection to the input cell number maximum value calculation unit 1005. The input cell number calculation unit 1003 includes an input cell number comparison unit 1007
When the input cell number output command signal is received from, the number of input cells being managed is output to the input cell number comparison unit 1007, and thereafter, the number of input cells being managed is all reset to “0”. However, when the operation of the communication element 1000 is started, the number of input cells of all connections is set to “0”.

The input cell number maximum value calculation unit 1005 manages the input cell number maximum value. Upon receiving the value of the number of input cells for each connection from the input cell number calculation unit 1003, the input cell number maximum value calculation unit 1005 compares the received input cell number value with the input cell number maximum value. If the received value of the number of input cells is larger, the maximum value of the number of input cells is updated to the value of the received number of input cells. However, when the operation of the communication element 1000 is started, the maximum value of the number of input cells is set to “0”. The input cell number maximum value calculation unit 1005 obtains the largest one among the plurality of received input cell numbers by the above operation. Then, the finally obtained maximum value of the number of input cells is output to input cell number threshold value calculation section 1006, and the managed maximum number of input cells is reset to “0”.

Upon receiving the input cell number maximum value from input cell number maximum value calculation section 1005, input cell number threshold value calculation section 1006 subtracts a preset constant from the received input cell number maximum value by inputting. Cell count threshold T
h_in is calculated and its value is output to the input cell number comparison unit 1007 (input cell number threshold value = input cell number maximum value−constant).

The input cell number comparison unit 1007 calculates the input cell number threshold value Th_in and the congestion notification flag Fcg of each connection.
When nf is managed and the input cell number threshold value Th_in is received, the managed input cell number threshold value Th_in is updated to the received value. And thereafter, the input cell number calculation unit 1
003 is output as an input cell number output command signal. Upon receiving the input cell number output command signal, the input cell number calculation unit 1003 outputs the number of input cells of each managed connection to the input cell number comparison unit 1007, and thereafter,
The number of input cells of each managed connection is reset to “0”. Upon receiving the number of input cells of each connection from the input cell number calculation unit 1003, the input cell number comparison unit 1007 receives the input cell number and the input cell number threshold T.
Compare with h_in. Based on the result of this comparison, if the input cell number is larger than the input cell number threshold Th_in, the input cell number comparison unit 1007 sets the value of the congestion notification flag Fcgnf of the connection to “1”, If the input cell number is smaller than the input cell number threshold Th_in, the value of the congestion notification flag Fcgnf of the connection is set to “0”. Then, the input cell number comparison unit 1007 receives the number of input cells of all connections, sets the value of the congestion notification flag Fcgnf of all connections, and stores the value of the congestion notification flag Fcgnf of each connection in the congestion notification table 1008. Output to

The EFCI bit setting unit 1009 manages the congestion determination flag Fcg. EFCI bit setting unit 1
009 sets the congestion judgment flag Fcg to “1” when receiving the congestion judgment signal from the congestion judgment unit 1002, and sets the congestion judgment flag Fcg to “0” when receiving the non-congestion judgment signal from the congestion judgment unit 1002. However, the communication element 100
When the operation starts at 0, the value of the congestion determination flag Fcg is “0”.
Is set to

The congestion notification table 1008 manages a congestion notification flag Fcgnf of each connection. Upon receiving the congestion notification flag Fcgnf of each connection from the input cell number comparison unit 1007, the congestion notification table 1008 updates the value of the managed congestion notification flag Fcgnf to the received value.

When receiving the data cell from queue 1001, EFCI bit setting section 1009 communicates the data cell without changing the value of the EFCI bit of the data cell when the value of congestion determination flag Fcg is “0”. Element 1010
Output to. If the value of the congestion determination flag Fcg is “1”, the EFCI bit setting unit 1009 calculates the connection number CN from the values of the VCI field and the VPI field of the data cell, and calculates the connection number CN.
Is output to the congestion notification table 1008. The congestion notification table 1008 includes an EFCI bit setting unit 1009
When the connection number CN is received from the EFCI bit setting unit 1009, the value of the congestion notification flag Fcgnf of the connection is referred to. In the case of "", the non-congestion notification command signal is sent to the EFCI bit setting unit 1009.
Output to The EFCI bit setting unit 1009
When receiving the non-congestion notification command signal, the EFC of the data cell
Without changing the value of the I bit, the data cell is
Output to 10 On the other hand, when receiving the congestion notification command signal, the EFCI bit setting unit 1009 sets the value of the EFCI bit of the data cell to “1”, and then outputs the data cell to the communication element 1010.

As described above, in this embodiment, as compared with the ninth embodiment, the maximum value of the number of input cells is calculated instead of the maximum value of the ACR, and the A value corresponding to the maximum value of the ACR is calculated.
Instead of setting the congestion notification flag Fcgnf based on the comparison between the CR threshold value and the ACR value of each connection, a comparison is made between the input cell number threshold value corresponding to the maximum input cell number value and the input cell number of each connection. Congestion notification flag Fcg
nf is set. However, except for these points, the basic operation in the present embodiment is the same as the operation in the ninth embodiment. That is, when the congestion determination flag Fcg is “1” and the congestion notification flag Fcgnf for the connection corresponding to the data cell received by the communication element 1000 is “1”, the EFCI bit of the data cell becomes “1”. , Which instructs the transmitting terminal to reduce the ACR value.

As described above, in this embodiment, the number of cells input by each connection during a certain length of measurement period, that is, the value of the input rate is observed, and congestion notification is sent only to connections whose value is close to the maximum value. Done. Therefore, according to the present embodiment, even in a communication network in which many communication elements are connected, the congestion notification is not concentrated on the connections passing through many communication elements, so that the connection between the connections related to the usage rate of the transmission band is not increased. Injustice is reduced.

In the above description, the embodiment has been described in which the congestion notification is performed using the EFCI bit of the data cell for a specific connection, but the CI bit or the ER field of the RM cell arriving at the communication element is used. An embodiment in which a congestion notification is performed by using an RM cell in a communication element and a congestion notification is performed using the CI bit or the ER field of the RM cell is also conceivable. Also, at the time of congestion, for the connection in which the congestion notification flag Fcgnf is “1”, the input bit rate is instructed by setting the CI bit of the RM cell, and the connection in which the congestion notification flag Fcgnf is “0” is set. On the other hand, an embodiment in which an increase in the input rate is prohibited by setting the NI bit of the RM cell is also conceivable.

In addition to the above operations, when the number of cells stored in the queue is very large and the congestion state of the communication element is serious, a congestion notification is performed for all connections. An embodiment in which the cell loss in the communication element is reduced while alleviating the unfairness between the connections regarding the usage rate of the transmission band is also conceivable.

Further, in the above-described embodiment, a congestion occurrence prediction unit is provided and a congestion prediction flag Fp_cg is introduced as in the third embodiment and the like. At the time of “1”, the NI bit of the RM cell is set to “1” for the connection for which the congestion notification flag Fcgnf is “1” in order to prevent a sudden increase in the input rate, thereby preventing the transmission terminal from transmitting. Alternatively, an instruction to prohibit an increase in the ACR may be issued.

<Eleventh Embodiment> Next, the eleventh embodiment of the present invention will be described.
A flow control method according to one embodiment will be described.
FIG. 15 is a block diagram illustrating a configuration of an ATM communication network including communication elements that execute the flow control method according to the present embodiment. This communication network includes terminals 1120, 1130, 114
0, and communication elements 1100 and 1110. The communication element 1100 includes a queue 1101 and a congestion determination unit 11
02, the parameter observation unit 1103, and the CCR observation unit 1
104, a timeout detection unit 1105, an ACR calculation unit 1106, a measurement period observation unit 1107, an ACR level calculation unit 1108, an ACR level management unit 1109,
ACR threshold calculator 1111 and ACR comparator 111
2, a congestion notification table 1113, and an EFCI bit setting unit 1114. Communication element 1110 and communication element 1
100 is connected by a communication path, and
0, 1130, and 1140 are the communication elements 110, respectively.
0 is connected by a communication path. In this example, the terminal 112
Information is transferred in the form of cells from the transmitting terminal accommodated in each of 0, 1130, and 1140 to the receiving terminal in the direction of the communication element 1110 through the communication element 1100. These cells are multiplexed in the queue 1101 of the communication element 1100 and output to the communication element 1110. In addition,
In this example, only one configuration for multiplexing is shown, but a similar configuration is required for each portion where cells are multiplexed and congestion occurs.

Next, the operation of each section of communication element 1100 will be described. The queue 1101, the congestion judging unit 1102, the parameter observing unit 1103, the CCR observing unit 1104, the timeout detecting unit 1105, and the measuring period observing unit 1107 perform the same operations as the corresponding parts in the third embodiment. Also, the ACR comparing unit 1112, the congestion notification table 1113, and the EFCI bit setting unit 1114 perform the same operations as the corresponding portions described in the ninth embodiment.

The ACR calculation unit 1106 manages the ACR value and the ICR value corresponding to the connection number CN of each connection using the ABR service.
When the ACR calculation unit 1106 receives the connection number CN and the value of the ICR from the parameter observation unit 1103, the ACR calculation unit 1106
A new storage area for managing the R value is secured, and its I
Both the CR and the ACR value are set to the received ICR value, and the ACR value (in this case, equal to the received ICR value) and the received connection number CN are output to the ACR level calculation unit 1108. Further, upon receiving the connection number CN and the CCR value from the CCR observation unit 1104, the ACR calculation unit 1106 sends the ACR value corresponding to the received connection number CN to the received CC.
It updates the R value, and outputs the updated ACR value and the received connection number CN to the ACR level calculation unit 1108. Further, upon receiving the connection number CN from the timeout detecting unit 1105, the ACR calculating unit 1106 receives the ACR corresponding to the received connection number CN.
The value is updated to the value of the ICR of the connection, and the ACR
The ACR value and the received connection number CN are output to the level calculation unit 1108.

The ACR level calculation unit 1108 manages the ACR level, and sets the level thresholds T (0), T (1), T (2),.
(N-1). Here, n level thresholds T (0) to T (n-1) are expressed as T (0) <T (1) <
It satisfies the relationship T (2) <... <T (n-1). The ACR level is set to “0” when the operation of the communication element 1100 starts. ACR level calculation unit 1108
Receives the connection number CN and the ACR value from the ACR calculation unit 1106, compares the received ACR value with the level threshold value T (0), and as a result, when the ACR value is smaller or equal to each other. , The ACR level (in this case, the value is “0”) and the received connection number CN are output to the ACR level management unit 1109, and the value of the ACR level is reset to “0”.
On the other hand, if the ACR value is larger than the level threshold value T (0), the ACR level calculation unit 1108 increases the ACR level by 1, and further increases the received ACR value and the level threshold value T (1). ) And compare. Thereafter, the same operation is repeated. That is, the received ACR value is compared with the level threshold value T (i). As a result, if the ACR value is smaller or equal, the ACR level (in this case, the value is i). ) And the received connection number CN to the ACR level management unit 1109, and resets the value of the ACR level to “0”. on the other hand,
If the ACR value is larger than the level threshold value T (i), the ACR level is increased by 1, and the received ACR value is compared with the level threshold value T (i + 1). Here, i represents any integer from 0 to n-2. As a result of the above repetition, if it is found that the ACR value is larger than the level threshold value T (n-1), A
After increasing the CR level by 1, the ACR level (in this case, the value is n) and the received connection number CN are output to the ACR level management unit 1109, and the value of the ACR level is set to "0". Reset to "".

The ACR level management unit 1109 manages the ACR level of each connection and the total number N (0), N (1),..., N (n) of (n + 1) variables. Upon receiving the connection number CN and the ACR level from the ACR level calculation unit 1108, the ACR level management unit 1109 first refers to the managed ACR level of the connection, and checks the ACR level of the connection.
If a level is defined, the total number of (n + 1) managed levels N (0) to N based on the value is defined.
Decrease some values of (n) by one. That is, assuming that the ACR level of the connection is i, the value of the total number of levels N (0), N (1),... After that, the ACR level of the connection is updated to the received value, and the received ACR level is updated.
Based on the CR level, some of the (n + 1) managed level total numbers N (0) to N (n) are increased by one. That is, the received ACR level is K
Then, the total number of levels N (0), N (1),.
All the values of (K) are increased by one. By performing the above operation, the ACR level management unit 1109 determines the number of connections having an ACR level of K or more as the total level number N.
Calculate as (K). However, when the operation of the communication element 1100 starts, the ACR level of each connection is “0”.
And the total number of each level is N (0) = n, N (1) =
, N (n) = 0. Upon receiving the measurement period end signal from the measurement period observation unit 1107, the ACR level management unit 1109 receives the total number of levels N (0), N (N).
The values of (1),..., N (n) are calculated by the ACR threshold calculator 11.
11 is output.

The ACR threshold calculator 1111 manages the value of the threshold calculation parameter CTh, the value of the counter, and the ACR threshold Th_ACR, and stores a preset input rate target value Tg_Rin. , And level thresholds T (0), T, which are n constants set in advance.
(1), T (2),..., T (n-1) are stored.
Here, the level threshold is determined by the ACR level calculation unit 110.
8 is the same value as the stored value. Also, the input rate target value Tg_Rin is a target value of the cell rate input to the queue 1101, and as will be described later, by setting this value to a value close to the output rate Rout of the queue, buffer overflow may occur in the queue. Performance can be reduced, and at the same time, the usage rate of the band can be improved. Also, the threshold calculation parameter CTh, the counter and the ACR threshold T
h_ACR is set to “0” when the operation of the communication element 1100 starts.

The ACR threshold calculator 1111 calculates the total number of levels N (0), N (1),.
When received from the level management unit 1109, the product of the value of the level threshold T (0) and the value of the total number of levels N (0) is calculated, and the value of the product is added to the value of the threshold calculation parameter CTh. Is newly stored as a threshold calculation parameter CTh (CTh = CTh + T (0) × N
(0)), the newly updated threshold calculation parameter C
The value of Th is compared with the input rate target value Tg_Rin. Based on the result of the comparison, the ACR threshold calculator 1111
If the value of the threshold calculation parameter CTh is larger than the input rate target value Tg_Rin, the ACR threshold T
h_ACR is set to “0”, and the value is set to the ACR comparing unit 111
2 to reset the threshold value calculation parameter CTh and the counter value to “0”. On the other hand, as a result of the comparison, if the value of the threshold value calculation parameter CTh is smaller than the input rate target value Tg_Rin or both are equal, the value of the counter is increased by 1 and then ΔT
(1) −T (0)｝ × N (1) is calculated, the value is added to the value of the threshold calculation parameter CTh, and the result is newly stored as the threshold calculation parameter CTh.
That is, the threshold calculation parameter CTh is updated by the following relational expression. CTh = CTh + {T (1) -T (0)} × N (1) Then, after performing the above update, the newly updated value of the threshold calculation parameter CTh and the input rate target value Tg
Compare with _Rin. As a result of the comparison, if the value of the threshold calculation parameter CTh is larger than the input rate target value Tg_Rin, the ACR threshold
The R threshold value Th_ACR is set as the level threshold value T (0), the value is output to the ACR comparison unit 1112, and the threshold value calculation parameter CTh and the counter value are reset to “0”. On the other hand, as a result of the comparison, if the value of threshold calculation parameter CTh is smaller than or equal to input rate target value Tg_Rin, the value of the counter is increased by 1 and the same operation is repeated thereafter. That is,
When the value of the counter becomes i, the ACR threshold value calculation unit 1111 outputs {T (i) −T (i−1)} × N
The value of (i) is calculated, the value is added to the value of the threshold calculation parameter CTh, and the result is newly stored as the threshold calculation parameter CTh. That is, the threshold calculation parameter CTh is updated by the following relational expression. CTh = CTh + {T (i) -T (i-1)} × N
(I) Then, after performing the above update, the newly updated value of the threshold calculation parameter CTh and the input rate target value Tg
Compare with _Rin. Here, i represents an arbitrary integer of 1 or more and (n-1) or less.

FIG. 19 is a diagram showing an example of the distribution of the input rate of each connection. In this example, the input rate for the C (i) connections is the level threshold T
It is assumed that the input rate is equal to (i) and the input rate is greater than the level threshold T (n-1) for C (n) connections (1 ≦ i ≦ n−1). In FIG. 19, T (j) represents a level threshold value (0 ≦ j ≦ n−
1) and N (k) represent the total number of levels (0 ≦ k ≦
n). The value of the threshold calculation parameter CTh when the value of the counter is i corresponds to the area of the portion shown as the threshold calculation parameter CTh (i) in FIG. As can be seen from FIG. 19, this value is input from all connections when the input rate of a connection whose input rate is higher than the level threshold T (i) is equal to the level threshold T (i). This is the total input rate.

If the value of threshold calculation parameter CTh is greater than target input rate Tg_Rin as a result of comparison between threshold calculation parameter CTh and input rate target value Tg_Rin, the value of the counter at this time is set to i (1 ≤i≤n-
Assuming 1), the following relational expression holds. CTh (i)> Tg_Rin (14) CTh (i-1) ≦ Tg_Rin (15)

From the above relational expression (15), for the connection whose input rate is larger than the level threshold T (i-1), the input rate is changed to the level threshold T (i-1).
, The total input rate input from all connections is equal to or less than the input rate target value Tg_Rin. From the relational expression (14), when the input rate of a connection whose input rate is higher than the level threshold T (i) is equal to the level threshold T (i), the total input from all the connections The rate becomes larger than the input rate target value Tg_Rin. So, in this case,
When congestion notification is performed for a connection whose input rate is higher than the level threshold T (i-1), the total input rate becomes equal to or less than the input rate target value Tg_Rin, and congestion can be avoided. Also, the level threshold T (i-1)
Is the maximum level threshold that can avoid congestion,
An excessive rate decrease is not performed, and the total input rate becomes a value close to the input rate target value Tg_Rin, and there is little possibility that the bandwidth utilization rate is reduced due to the congestion notification, so that it is efficient. However, it is assumed that the input rate target value Tg_Rin is set to a value close to the transmission speed of the queue. In each connection, it is assumed that cell input is performed at a rate equal to the ACR.

Therefore, if the input rate is equal to the level threshold T
In order to instruct the connection larger than (i-1) to decrease the input rate, the ACR threshold calculator 11
11 indicates that if the value of the threshold calculation parameter CTh is larger than the input rate target value Tg_Rin as a result of the comparison between the threshold calculation parameter CTh and the input rate target value Tg_Rin, the value of the counter at this time is i. , ACR threshold Th_ACR is set as level threshold T (i-1),
The value is output to the ACR comparing unit 1112, and the threshold value calculation parameter CTh and the value of the counter are reset to “0”.

On the other hand, as a result of the comparison, if the value of threshold calculation parameter CTh is smaller than input rate target value Tg_Rin or both are equal, ACR threshold calculator 1
111 increments the value of the counter by one. Where i
Represents an arbitrary integer of 1 or more and (n-1) or less.

Further, ACR threshold value calculating section 1111
Sets the ACR threshold value Th_ACR as the level threshold value T (n-1) when the counter value reaches n, outputs the value to the ACR comparison unit 1112, and sets the threshold value calculation parameter CTh and the value of the counter are reset to “0”. In this case, the following relational expression holds. CTh (n-1) <Tg_Rin (16)

As described above, in the flow control method according to the present embodiment, the preset n level thresholds T
An ACR level corresponding to the ACR value is obtained for each connection based on (0), T (1),..., T (n-1), and the distribution of the ACR value for each connection is determined based on the ACR level. Based on the distribution of the ACR values, the connection for performing the congestion notification is selected such that the sum of the ACR values becomes close to the input rate target value Tg_Rin. Then, in order to select a connection for performing congestion notification, the total number of levels N (0), N corresponding to (n + 1) ACR levels 0, 1,.
(1),..., N (n) are calculated, and the ACR threshold is determined based on a threshold calculation parameter CTh calculated using the total number of the levels. Therefore, in the following, a procedure for calculating the total number of levels N (0), N (1),..., N (n) (hereinafter referred to as a “procedure for calculating the total number of levels”) and the total number of these levels are ACR using
A procedure for calculating a threshold (hereinafter referred to as “ACR threshold calculation procedure”) will be described.

FIG. 16 is a flowchart showing a procedure for calculating the total number of levels by the communication element 1100 that executes the flow control method according to the present embodiment. In this flowchart, ACR [CN] represents the value of ACR for the connection with connection number CN, and the timer value [C
N] represents the timer value of the timer corresponding to the connection of connection number CN, ICR [CN] represents the value of ICR for the connection of connection number CN, and ADTF [CN] represents the value of ADTF for the connection of connection number CN. Representation, LACR [CN]
Is the ACR for the connection with connection number CN
Represents a level value. Note that N (i) represents the number of connections whose ACR level is i or higher, that is, the total number of levels.

As shown in FIG. 16, the procedure for calculating the total number of levels is started when any of the following events i) to iii) occurs. i) Arrival of a cell to the queue 1101 (hereinafter “cell arrival”)
Ii) The timer value of the timer corresponding to one of the connections is equal to the ADTF value of the connection (hereinafter referred to as "timeout") iii) Start of operation of the communication element 1100 (hereinafter referred to as "system operation start")

When the procedure for calculating the total number of levels is started by the start of the system operation (step S1190), the AC
The R level Lv_ACR and the total number of levels N (0) to N (n) are initialized as follows (step S1192). Lv_ACR = 0 N (0) = n N (1) = 0, N (2) = 0,..., N (n) = 0

When the procedure for calculating the total number of levels is started upon arrival of a cell (step S1100), communication element 1100
First, the queue 1001 outputs a queue length increase signal. The congestion determination unit 1102 according to the present embodiment is configured by a portion that functions similarly to the queue length observation unit 103 and the congestion determination unit 104 according to the first embodiment, and a queue length increase signal is output from the queue 1101. Then, the queue length L_que is increased by 1 (step S1102). Note that this queue length L_que
Is set to “0” when the operation of the communication element 1100 starts. When a cell is output from the queue 1101,
A queue length decrease signal is output from the queue 1101 to the congestion determination unit 1102, and the congestion determination unit 1102 outputs a queue length L_que.
By one (not shown).

After that, the type of the cell arriving at the queue 1101 is determined by each of the parameter observing section 1103 and the CCR observing section 1104 (step S1).
104). As a result, if the cell is a signaling cell for ABR service connection setup,
The following processing is performed. That is, the parameter observation unit 1103 detects the ICR value of the connection and the connection number CN from the cell,
In calculation unit 1106, A for the connection
The value of CR is set to the value of ICR (step S1).
106). When the ACR value is set for the connection corresponding to the above-mentioned signaling cell arriving at the queue 1101, the process proceeds to step S1140.

The type of the cell arriving at the queue 1101 is determined by the CCR observation unit 1104 (step S
1104, S1112) As a result, if the cell is an RM cell, the CCR observation unit 1104 obtains a CCR value from the RM cell and calculates a connection number CN corresponding to the RM cell (step S1112). S
1124). This connection number CN is output to timeout detecting section 1105. Further, the CCR value and the connection number CN are output to the ACR calculation section 1106, and the ACR value of the connection is updated to the CCR value in the ACR calculation section 1106 (Step S).
1126). When the connection number CN is output to the timeout detection unit 1105, the timer corresponding to the connection number CN sets the timer value to “0”.
(Step S112)
8). In this way, when the value of the ACR is set for the connection corresponding to the RM cell arriving at the queue 1101 and the timer starts, at step S11
Proceed to 40.

In step S1128 described above, after the timer corresponding to a certain connection is started with its timer value initialized to “0”, the elapsed time from the start time, that is, the timer value is changed to the value of the ADTF of the connection. (S1130), the time-out triggers the level total number calculation procedure. In this case, the connection number CN corresponding to the timeout is sent from the timeout detection unit 1105 to the ACR calculation unit 1.
Output to 106. If this connection number CN is AC
When received by the R calculation unit 1106, the value of the ACR corresponding to the connection number CN is set to the value of the ICR of the connection (step S1132).
The value of this ACR together with the connection number CN is AC
Output to R level calculation section 1108. When the ACR value for the connection corresponding to the timeout is set to the ICR value in this way, the process proceeds to step S1140.

If it is determined that the cell arriving at queue 1101 is neither a signaling cell nor an RM cell (step S1112), ACR calculating section 1106 does not change the held ACR value, and Then, the procedure for calculating the total number of levels is completed without setting a new ACR value.

When the process proceeds to step S1140, A
In the CR level calculation unit 1108,
The ACR level for the connection with connection number CN output from ACR calculation section 1106 is determined. That is, first, the ACR value for the connection number CN output from the ACR calculation unit 1106 is compared with the level threshold T (Lv_ACR) (at first, Lv_ACR =
0). As a result, the ACR value becomes the level threshold value T (L
(v_ACR), the Lv_ACR is increased by 1 (step S1142), and then the ACR level Lv_A
It is determined whether or not CR is equal to the number n of the level thresholds (step S1144). As a result, if Lv_ACR is not equal to n, that is, if Lv_ACR <n, the process returns to step S1140. Hereafter, the connection number CN
While the ACR [CN] which is the ACR value corresponding to is larger than the level threshold T (Lv_ACR) and the Lv_ACR is smaller than n, steps S1140 → S1142 →
S1144 is repeatedly executed. Meanwhile, ACR [C
N] becomes equal to or less than T (Lv_ACR) or Lv_ACR becomes equal to n, the flow proceeds to step S1146. At this point, the ACR level corresponding to the ACR value for the connection with the connection number CN is set in Lv_ACR. In step S1146, this Lv_ACR is set to k (step S1146), and then Lv_ACR is reset to “0” (step S1148). The ACR level k for the connection number CN is:
ACR level management unit 1 together with the connection number CN
It is output to 109.

Thereafter, the ACR level management unit 1109 sets or updates the total number of levels as follows using the connection number CN output to the ACR level management unit 1109 and the corresponding ACR level k. . First, it is determined whether or not LACR [CN] which is the ACR level corresponding to the connection number CN is defined (step S1150). As a result, LACR
If [CN] is defined, its LACR [C
N] is set to i (step S1152), and each of the total number of levels N (0), N (1),..., N (i) is decreased by 1 (step S1154). Next, LACR [C which is the ACR level corresponding to the connection number CN
N] is set to the value of k, and the total number of levels N (0), N
Each of (1),..., N (k) is increased by 1 (step S1156). On the other hand, if it is determined in step S1150 that LACR [CN] is not defined, LACR [CN] is set to the value of k without executing steps S1152 and S1154.
Each of (0), N (1),..., N (k) is incremented by 1 (step S1156).

When the total number of levels is set or updated in accordance with the ACR value for the connection corresponding to the cell arriving at queue 1101, the procedure for calculating the total number of levels is terminated. In the ACR threshold calculation procedure described below, the ACR level threshold is calculated using the total number of levels set or changed in this way.

FIG. 17 is a flowchart showing an ACR threshold setting procedure by the communication element 1100 executing the flow control method according to the present embodiment. The ACR threshold setting procedure is started when any of the following events i) and ii) occurs. i) Output of a measurement period end signal (hereinafter, this event is referred to as “measurement period end”) The measurement period end signal is output from the measurement period observation unit 1107 to the ACR level management unit 1109 at a preset time interval. ii) Start operation of communication element 1100 (start system operation)

When the ACR threshold calculation procedure is started at the start of system operation (step S1195), the variable i relating to the level threshold and the threshold calculation parameter CTh are initialized to “0” (step S1195). S119
7).

When the ACR threshold value calculation procedure is started by the end of the measurement period (step S1160), the communication element 1
100 operates as follows.

First, the ACR level management unit 1109 sends A
The CR total number N is added to the CR threshold value calculation unit 1111.
(0), N (1),..., N (n) are output. AC
The R threshold calculator 1111 calculates the total number of these levels and a preset input rate target value Tg_Rin (this value is set to a value close to the queue output rate Rout).
Based on the above, the ACR threshold is calculated as follows.

First, a value obtained by adding the product of the level threshold value T (0) and the total number of levels N (0) to the threshold value calculation parameter CTh, that is, CTh + T (0) × N (0) is newly added. The threshold value calculation parameter CTh is set (step S1162). Note that CTh is initialized to “0” at the start of system operation as described above.

Next, a new threshold value calculation parameter CT
h is compared with the input target value Tg_Rin (step S116).
4). As a result, if the threshold calculation parameter CTh is larger than the input rate target value Tg_Rin, the process advances to step S1180 to set the ACR threshold Th_ACR to “0” in order to perform congestion notification for all connections. Set. After that, both the threshold calculation parameter CTh and the variable i are reset to “0”, and the ACR threshold calculation procedure ends.

As a result of the determination in step S1164, threshold value calculation parameter CTh is set to input rate target value Tg_Rin.
In the following cases, the variable i is increased by 1 (step S1166). As described above, the variable i is initialized to “0” during system operation. After increasing the variable i by 1, the value calculated by the following equation is used as a new threshold value calculation parameter CTh (step S1).
168). CTh + {T (i) -T (i-1)} × N (i) Thereafter, the new threshold value calculation parameter CTh is compared with the input rate target value Tg_Rin (step S117).
0). As a result, if the threshold calculation parameter CTh is equal to or smaller than the input parameter Tg_Rin, the variable i is increased by 1 (step S1172). Thereafter, it is determined whether or not the variable i is equal to the number n of the level thresholds. A determination is made (step S1174). As a result, if the variable i is not equal to n, that is, if i <n, the process returns to step S1168. Thereafter, while the threshold value calculation parameter CTh is equal to or smaller than the input rate target value Tg_Rin and the variable i is smaller than n, steps S1168 → S1170 → S1174 are repeatedly executed. Meanwhile, the threshold calculation parameter C
Th is larger than the input rate target value Tg_Rin,
Alternatively, if the variable i becomes equal to n, the process proceeds to step S1176.

[0282] In step S1176, the level threshold T (i-1) is set so that congestion notification is performed for a connection whose ACR value is larger than the level threshold T (i-1).
Is set as the ACR threshold Th_ACR. After that, the threshold calculation parameter CTh is reset to “0”, the variable i is reset to “0”, and the ACR threshold calculation procedure ends.

The ACR threshold value Th_ACR set as described above is the same as that of the ninth embodiment.
At 112, the ACR value for each connection is compared. As a result, the ACR value becomes equal to the ACR threshold Th_ACR
Congestion notification flag F for connections larger than
cgnf is set to “1”, and the congestion notification flag Fcgnf is set to “0” for a connection whose ACR value is equal to or smaller than the ACR threshold Th_ACR. The congestion notification flag Fcgnf set for each connection in this manner is managed in the congestion notification table 1113. ECF
The I bit setting unit 1114 sets the EFCI bit for the data cell based on the congestion notification flag Fcgnf in the same manner as in the ninth embodiment and the like.

As described above, in the present embodiment, when the congestion determination flag Fcg is “1”, the communication element 110
When the congestion notification flag Fcgnf for the connection corresponding to the data cell received by the “0” is “1”, the EFCI bit of the data cell is set to “1”, whereby the value of the ACR is transmitted to the transmitting terminal. Reduction is indicated. That is, in the present embodiment, the AC of each connection is
An R value is calculated, and congestion notification is performed only for connections having a large R value. At this time, as a result of the congestion notification, the ACR
Are selected such that the sum of the values is close to the input rate target value Tg_Rin. Therefore, according to the present embodiment, even in a communication network in which many communication elements are connected, the congestion notification is not concentrated on the connections passing through many communication elements, so that the connection between the connections related to the usage rate of the transmission band is not increased. Injustice is reduced.
Furthermore, at the time of the congestion notification, the sum of the input rates from each connection quickly converges to the input rate target value Tg_Rin. Therefore, if the input rate target value Tg_Rin is set to a value close to the transmission speed of the queue, the buffer overflows in the queue. The likelihood of occurrence can be reduced. In addition, since the ACR total value quickly converges to the input rate target value Tg_Rin, the input rate does not decrease to an extremely small value due to excessive congestion notification, so that the transmission band can be effectively used.

[0285] In the above, the embodiment in which congestion notification is performed using the EFCI bit of the data cell for a specific connection has been described. An embodiment in which a congestion notification is performed by using an RM cell in a communication element and a congestion notification is performed using the CI bit or the ER field of the RM cell is also conceivable. Also, at the time of congestion, for the connection in which the congestion notification flag Fcgnf is “1”, the input bit rate is instructed by setting the CI bit of the RM cell, and the connection in which the congestion notification flag Fcgnf is “0” is set. On the other hand, an embodiment in which an increase in the input rate is prohibited by setting the NI bit of the RM cell is also conceivable.

In addition to the above operation, when the number of cells stored in the queue is very large and the congestion state of the communication element is serious, a congestion notification is performed for all connections, thereby An embodiment in which the cell loss in the communication element is reduced while alleviating the unfairness between the connections regarding the usage rate of the transmission band is also conceivable.

Further, in the above-described embodiment, a congestion occurrence prediction unit is provided and a congestion prediction flag Fp_cg is introduced as in the third embodiment and the like, and the congestion determination flag Fcg is set to “0” and the congestion prediction flag Fp_cg is set to “ At the time of “1”, the NI bit of the RM cell is set to “1” for the connection for which the congestion notification flag Fcgnf is “1” in order to prevent a sudden increase in the input rate, thereby preventing the transmission terminal from transmitting. A prohibition of the increase of the ACR may be instructed.

<Twelfth Embodiment> Next, the first embodiment of the present invention will be described.
A flow control method according to the second embodiment will be described.
FIG. 18 is a block diagram illustrating a configuration of an ATM communication network including communication elements that execute the flow control method according to the present embodiment. This communication network includes terminals 1220, 1230, and 124.
0, and communication elements 1200 and 1210. The communication element 1200 includes a queue 1201 and a congestion determination unit 12.
02, input cell number calculation section 1203, measurement period observation section 1204, cell number level calculation section 1205, cell number level management section 1206, input cell number threshold value calculation section 12
07, an input cell number comparison unit 1208, a congestion notification table 1209, and an EFCI bit setting unit 1211. The communication element 1210 and the communication element 1200 are connected by a communication path, and the terminals 1220, 1230, 1212
Each 40 is connected to the communication element 1200 via a communication path. In this example, terminals 1220, 1230, 12
40, the communication element 1
200 to the receiving terminal in the direction of the communication element 1210,
Transferring information in the form of cells. These cells are multiplexed in the queue 1201 of the communication element 1200 and output to the communication element 1210. In this example,
Although only one configuration for multiplexing is shown, a similar configuration is required for each portion where cells are multiplexed and congestion occurs.

Next, the operation of each section of communication element 1200 will be described. The queue 1201, the congestion determination unit 1202, and the measurement period observation unit 1204 perform the same operations as the corresponding parts in the third embodiment. Also, a congestion notification table 1209, an EFCI bit setting unit 1211,
The input cell number comparison unit 1208 performs the same operation as the corresponding part in the tenth embodiment.

The input cell number calculation unit 1203 manages the input cell number and the cell number counter for each connection, and when receiving the connection number CN from the queue 1201, increases the cell number counter of the connection by one. However, when the operation of the communication element 1200 is started, the input cell number and the cell number counter are all set to “0”. Upon receiving the measurement period end signal from the measurement period observation unit 1204, the input cell number calculation unit 1203 copies the value of the cell number counter to the value of the input cell number for each connection, and then copies the value of the cell number counter. Is reset to “0”, and the number of input cells of each connection is output to the cell number level calculation unit 1205. Further, upon receiving the input cell number output command signal from the input cell number comparison unit 1208, the input cell number calculation unit 1203 outputs the number of input cells of each managed connection to the input cell number comparison unit 1208.

The cell number level calculation section 1205 manages the cell number level for each connection, and sets level thresholds T (0), T
(1), T (2),..., T (n-1) are stored.
Here, n level thresholds T (0) to T (n-1)
Is T (0) <T (1) <T (2) <... <T (n-1)
Satisfy the relationship. Also, the cell number level is the communication element 120.
It is set to “0” when the operation of “0” starts. Upon receiving the number of input cells from the input cell number calculation unit 1203, the cell number level calculation unit 1205 performs the following operation for each connection.

First, cell number level calculating section 1205 compares the received number of input cells with level threshold value T (0), and as a result, if the number of input cells is smaller or equal to each other, The cell number level (in this case, the value is “0”) and the connection number CN are output to the cell number level management unit 1206, and the value of the cell number level is reset to “0”. On the other hand, if the number of input cells is equal to the level threshold T
If it is larger than (0), the cell number level is increased by 1, and the received input cell number is compared with the level threshold T (1). Thereafter, the same operation is repeated. That is, the received number of input cells is compared with the level threshold value T (i), and as a result, if the number of input cells is smaller or equal, the cell number level (in this case, the value is i ) And the connection number CN are output to the cell number level management unit 1206, and the value of the cell number level is reset to “0”. On the other hand, if the number of input cells is larger than the level threshold T (i), the number of cells is increased by one, and the received number of input cells is compared with the level threshold T (i + 1). I do. here,
i represents any integer of 0 or more and n-2 or less. As a result of the above repetition, the number of input cells reaches the level threshold T (n-
If it is found that the number is larger than 1), the cell number level is increased by 1, and then the cell number level (in this case, the value is n) and the received connection number CN are managed. The value is output to the unit 1206, and the value of the cell number level is reset to “0”.

The cell number level calculation unit 1205 performs the above operation on each connection, thereby changing the cell number level of all connections to the cell number level management unit 12.
06 is output.

The cell number level management unit 1206 manages the cell number level of each connection and the total number N (0), N (1),..., N (n) of (n + 1) variables. I have. When receiving the cell number level of each connection from the cell number level calculation unit 1205, the cell number level management unit 1206 first refers to the cell number level of the managed connection, and defines the cell number level of the connection. If so, based on that value, the value of some of the (n + 1) level total numbers N (0) to N (n) managed is reduced by one. That is, if the cell number level of the connection is i, the value of the total number of levels N (0), N (1),... After that, the cell number level of the connection is updated to the received value, and based on the received cell number level, the number of the (n + 1) level total numbers N (0) to N (n) managed is determined. Is increased by one. That is, assuming that the received cell number level is K, the total number of levels N (0), N (1),..., N (K)
Are all increased by one. Cell number level management unit 12
06, by performing the above operations, the number of connections whose cell number level is equal to or higher than K is calculated as the total number of levels N (K).
Is calculated as However, when the operation of the communication element 1200 is started, the cell number level of each connection is “0”, and the total number of levels is N (0) = n, N (1) = 0,
.., N (n) = 0. When the above operation is completed for all connections, the cell number level management unit 1206 completes the total number of levels N (0), N (1),.
The value of N (n) is output to input cell number threshold value calculation section 1207.

The input cell number threshold value calculation unit 1207 manages the value of the threshold value calculation parameter CTh, the value of the counter, and the input cell number threshold value Th_in, and calculates the preset input rate target value Tg_Rin. And a level threshold T which is a preset number of n constants.
(0), T (1), T (2),..., T (n−1) are stored. Here, the level threshold value is the same value as the value stored in cell number level calculation section 1205. Also,
The input rate target value Tg_Rin is a target value of the cell rate input to the queue 1201, and by setting this value to a value close to the output rate Rout of the queue as will be described later, the possibility of buffer overflow in the queue may occur. It is possible to reduce the size and at the same time improve the usage rate of the band. Further, the threshold value calculation parameter CTh, the counter, and the input cell number threshold value Th_in are set to “0” when the operation of the communication element 1200 is started.

Upon receiving the values of the total number of levels N (0), N (1),..., N (n) from the number-of-cells level management section 1206, the input cell number threshold value calculation section 1207 receives the level threshold value. The product of the value of T (0) and the value of the total number of levels N (0) is calculated, the value of the product is added to the value of the threshold calculation parameter CTh, and the result is newly set as the threshold calculation parameter CTh. (CTh = CTh + T (0) × N
(0)), the newly updated threshold calculation parameter C
The value of Th is compared with the input rate target value Tg_Rin. Based on the result of the comparison, the input cell number threshold calculator 12
07 sets the input cell number threshold value Th_in to “0” when the value of the threshold value calculation parameter CTh is larger than the input rate target value Tg_Rin, and sends the value to the input cell number comparison unit 1208. And resets the threshold calculation parameter CTh and the value of the counter to “0”. on the other hand,
As a result of the comparison, when the value of the threshold calculation parameter CTh is smaller than the input rate target value Tg_Rin or both are equal, the value of the counter is increased by 1 and thereafter,
Calculate the value of {T (1) −T (0)} × N (1), add the value to the value of threshold calculation parameter CTh, and store the result as threshold calculation parameter CTh. . That is, the threshold calculation parameter CTh is updated by the following relational expression. CTh = CTh + {T (1) -T (0)} × N (1) Then, after performing the above update, the newly updated value of the threshold calculation parameter CTh and the input rate target value Tg
Compare with _Rin. As a result of the comparison, when the value of the threshold calculation parameter CTh is larger than the input rate target value Tg_Rin, the input cell number threshold Th_in is set as the level threshold T (0), and the value is input. Cell number comparison unit 12
08, and resets the threshold calculation parameter CTh and the value of the counter to “0”. On the other hand, as a result of the comparison, if the value of threshold calculation parameter CTh is smaller than or equal to input rate target value Tg_Rin, the value of the counter is increased by 1 and the same operation is repeated thereafter. That is, the input cell number threshold value calculation unit 1
207 is ΔT when the value of the counter becomes i.
(I) -T (i-1)｝ × N (i) is calculated, the value is added to the value of the threshold calculation parameter CTh, and the result is newly stored as the threshold calculation parameter CTh. . That is, the threshold calculation parameter CTh is updated by the following relational expression. CTh = CTh + {T (i) -T (i-1)} × N
(I) Then, after performing the above update, the newly updated value of the threshold calculation parameter CTh and the input rate target value Tg
Compare with _Rin. Here, i represents an arbitrary integer of 1 or more and (n-1) or less.

FIG. 19 is a diagram showing an example of the distribution of the input rate of each connection. In this example, C (i)
For the number of connections, the number of input cells in the measurement period is equal to the level threshold T (i), and for the number of C (n) connections, the number of input cells is the level threshold T (n-1).
Greater than (1 ≦ i ≦ n−
1). In FIG. 19, T (j) represents a level threshold (0 ≦ j ≦ n−1), and N (k) represents the total number of levels (0 ≦ k ≦ n). The value of the threshold calculation parameter CTh when the value of the counter is i corresponds to the area of the portion indicated by the threshold calculation parameter CTh (i) in FIG. As can be seen from FIG. 19, this value is calculated by changing the number of input cells of a connection in which the number of input cells within the measurement period is larger than the level threshold T (i) to the level threshold T (i).
This is the total number of cells input within the measurement period from all connections when equal to (i).

If the value of threshold calculation parameter CTh is larger than target input rate Tg_Rin as a result of comparison between threshold calculation parameter CTh and input rate target value Tg_Rin, the value of the counter at this time is set to i (1 ≤i≤n-
Assuming 1), the following relational expression holds. CTh (i)> Tg_Rin (17) CTh (i-1) ≦ Tg_Rin (18)

According to the above relational expression (18), for a connection in which the number of input cells within the measurement period is larger than the level threshold T (i-1), the number of input cells is changed to the level threshold T (i-1). , The total number of cells input from all connections during the measurement period is the input rate target value T
g_Rin or less. From the relational expression (17), when the number of input cells is equal to the level threshold T (i) for a connection in which the number of input cells in the measurement period is larger than the level threshold T (i), all connections The total number of cells input from within the measurement period is the input rate target value Tg
Greater than _Rin. Therefore, in this case, if congestion notification is performed for a connection in which the number of input cells is greater than the level threshold T (i-1), the total input rate will be equal to or less than the input rate target value Tg_Rin to avoid congestion. Can be. Also, since the level threshold T (i-1) is the maximum level threshold that can avoid congestion, no excessive rate reduction is performed, and the total input rate becomes a value close to the input rate target value Tg_Rin, and congestion occurs. The possibility of lowering the bandwidth usage rate due to the notification is small and efficient. However, it is assumed that the input rate target value Tg_Rin is set to a value close to the transmission speed of the queue.

Therefore, the number of input cells is equal to the level threshold T.
In order to instruct the connection larger than (i-1) to decrease the input rate, the input cell number threshold value calculating unit 1207 compares the threshold value calculation parameter CTh with the input rate target value Tg_Rin. If the value of the threshold calculation parameter CTh is larger than the input rate target value Tg_Rin, and if the value of the counter at this time is i, the input cell number threshold Th_in is set to the level threshold T (i-1). The threshold value is output to the input cell number comparison unit 1208, and the threshold value calculation parameter CTh and the counter value are reset to “0”.

On the other hand, as a result of comparison between threshold value calculation parameter CTh and input rate target value Tg_Rin, if the value of threshold value calculation parameter CTh is smaller than input rate target value Tg_Rin or both are equal, counter Is increased by one. Here, i represents an arbitrary integer of 1 or more and (n-1) or less.

Further, input cell number threshold value calculating section 120
7 sets the input cell number threshold value Th_in as the level threshold value T (n-1) when the counter value reaches n, and outputs the value to the input cell number comparison unit 1208; The threshold value calculation parameter CTh and the value of the counter are reset to “0”. In this case, the following relational expression holds. CTh (n-1) <Tg_Rin (19)

The input cell number threshold value Th_in set as described above is compared with the number of input cells for each connection in the input cell number comparison section 1208 as in the tenth embodiment. As a result, the congestion notification flag Fcgnf is set to "1" for a connection in which the number of input cells is larger than the threshold value Th_in of the input cell number, and the connection in which the number of input cells is equal to or less than the threshold value Th_in of the input cell number is set. On the other hand, the congestion notification flag Fcgnf is set to “0”. The congestion notification flag Fcgnf set for each connection in this manner is managed in the congestion notification table 1209. The ECFI bit setting unit 1211 sets the EFCI bit for the data cell based on the congestion notification flag Fcgnf in the same manner as in the tenth embodiment and the like.

As described above, the present embodiment differs from the eleventh embodiment in that the A
Instead of calculating the ACR threshold based on the CR value distribution and the preset input target rate, the input cell number threshold is determined based on the distribution of the input cell number for each connection and the preset input target rate. The value Th_in is calculated and A
Instead of setting the congestion notification flag Fcgnf based on the comparison between the CR threshold and the ACR value of each connection, the congestion notification flag Fcgnf is set based on a comparison between the input cell number threshold Th_in and the number of input cells of each connection. Is done. However, except for these points, the basic operation in this embodiment is the same as the operation in the eleventh embodiment. That is, when the congestion determination flag Fcg is “1”, the congestion notification flag Fcgnf for the connection corresponding to the data cell received by the communication element 1200 is “1”.
, The EFCI bit of the data cell is set to “1”, which causes
An instruction is issued to reduce the value of R.

As described above, in the present embodiment, the number of cells input in each connection during a certain length measurement period,
That is, the value of the input rate is observed, and congestion notification is performed only for connections having a large value. At this time, as a result of the congestion notification, the sum of the input rates is equal to the input rate target value Tg.
The connection for performing the congestion notification is selected so that the value is close to _Rin. Therefore, according to the present embodiment, even in a communication network in which many communication elements are connected, the congestion notification is not concentrated on the connections passing through many communication elements, so that the connection between the connections related to the usage rate of the transmission band is not increased. Injustice is reduced. Further, at the time of the congestion notification, the sum of the input rates from the respective connections is equal to the input rate target value T.
Since it quickly converges to g_Rin, the input rate target value Tg_R
Setting in to a value close to the transmission speed of the queue can reduce the possibility of buffer overflow in the queue. In addition, since the input rate total value quickly converges to the input rate target value Tg_Rin, the input rate does not decrease to an extremely small value due to excessive congestion notification, so that the transmission band can be effectively used.

In the above description, the embodiment has been described in which the EFCI bit of the data cell is used to notify congestion for a specific connection. An embodiment in which a congestion notification is performed by using an RM cell in a communication element and a congestion notification is performed using the CI bit or the ER field of the RM cell is also conceivable. Also, at the time of congestion, for the connection in which the congestion notification flag Fcgnf is “1”, the input bit rate is instructed by setting the CI bit of the RM cell, and the connection in which the congestion notification flag Fcgnf is “0” is set. On the other hand, an embodiment in which an increase in the input rate is prohibited by setting the NI bit of the RM cell is also conceivable.

In addition to the above operations, when the number of cells stored in the queue is very large and the congestion state of the communication element is serious, a congestion notification is made for all connections, thereby An embodiment in which the cell loss in the communication element is reduced while alleviating the unfairness between the connections regarding the usage rate of the transmission band is also conceivable.

Further, in the above embodiment, a congestion occurrence prediction unit is provided and a congestion prediction flag Fp_cg is introduced as in the third embodiment and the like, and the congestion determination flag Fcg is "0" and the congestion prediction flag Fp_cg is " At the time of “1”, the NI bit of the RM cell is set to “1” for the connection for which the congestion notification flag Fcgnf is “1” in order to prevent a sudden increase in the input rate, thereby preventing the transmission terminal from transmitting. A prohibition of the increase of the ACR may be instructed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an ATM communication network including a communication element that executes a flow control method according to a first embodiment of the present invention.

FIG. 2 is a flowchart illustrating a procedure for setting a congestion prediction flag according to the first embodiment;

FIG. 3 is a block diagram showing a configuration of an ATM communication network including communication elements that execute a flow control method according to a second embodiment of the present invention.

FIG. 4 is a flowchart illustrating a procedure for setting a congestion prediction flag according to the second embodiment;

FIG. 5 is a block diagram showing a configuration of an ATM communication network including a communication element that executes a flow control method according to a third embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of an ATM communication network including communication elements that execute a flow control method according to a fourth embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of an ATM communication network including a communication element that executes a flow control method according to a fifth embodiment of the present invention.

FIG. 8 is a block diagram showing a configuration of an ATM communication network including a communication element that executes a flow control method according to a sixth embodiment of the present invention.

FIG. 9 is a block diagram showing a configuration of an ATM communication network including communication elements that execute a flow control method according to a seventh embodiment of the present invention.

FIG. 10 is a block diagram showing a configuration of an ATM communication network including communication elements that execute a flow control method according to an eighth embodiment of the present invention.

FIG. 11 is a block diagram showing a configuration of an ATM communication network including communication elements that execute a flow control method according to a ninth embodiment of the present invention.

FIG. 12 is a flowchart illustrating an ACR calculation procedure according to the ninth embodiment.

FIG. 13 is a flowchart illustrating a congestion notification flag setting procedure according to the ninth embodiment;

FIG. 14 is a block diagram showing a configuration of an ATM communication network including a communication element that executes a flow control method according to a tenth embodiment of the present invention.

FIG. 15 is a block diagram showing a configuration of an ATM communication network including communication elements that execute a flow control method according to an eleventh embodiment of the present invention.

FIG. 16 is a flowchart showing a procedure for calculating the total number of levels in the eleventh embodiment.

FIG. 17 is a flowchart illustrating an ACR threshold value calculation procedure according to the eleventh embodiment.

FIG. 18 is a block diagram showing a configuration of an ATM communication network including a communication element that executes a flow control method according to a twelfth embodiment of the present invention.

FIG. 19 is a diagram showing a distribution example of an input rate of each connection in the eleventh and twelfth embodiments.

FIG. 20 is a block diagram showing an example of the configuration of an ATM communication network including a communication element that executes a flow control method of a conventional example.

FIG. 21 is a diagram illustrating an example of a change in a queue length and an input rate when connections that generate data having a large burst property are multiplexed using a conventional flow control method.

FIG. 22 is a block diagram illustrating a configuration example of a communication network in which connections that generate data having a large burst property are multiplexed using a conventional flow control method.

FIG. 23 is a block diagram showing a configuration example of a communication network including many communication elements.

FIG. 24 is a diagram illustrating an example of a change in queue length and input rate when a conventional flow control method is applied to a communication network including many communication elements.

[Explanation of symbols]

Reference Signs List 100 communication element 101 queue 102 parameter observation unit 103 queue length observation unit 104 congestion determination unit 105 FR
TT calculation unit 106 CCR observation unit 107 Timeout detection unit 108 ACR calculation unit 109 AC
R total value calculation unit 111: ACR total value threshold value calculation unit 112: congestion occurrence prediction unit 113: EFCI bit setting unit 120, 13
0, 140 terminal 110 communication element 200, 210 communication element 201 queue 202 parameter observation section 203 queue length observation section 204 congestion determination section 205 FR
TT calculation unit 206 CCR observation unit 207 Timeout detection unit 208 ACR calculation unit 209 Maximum input cell number prediction unit 211 Congestion prediction threshold calculation unit 212 Congestion occurrence prediction unit 213 EFCI bit setting units 220 and 23
0, 240 terminal 300, 310 communication element 301 queue 302 congestion determination unit 303 congestion occurrence prediction unit 304 parameter observation unit 305 CC
R observation unit 306: timeout detection unit 307: AC
R calculation section 308: inactivity determination threshold value calculation section 309: measurement period observation section 311: CC
R observation unit 312 ... congestion notification table 313 ... EF
CI bit setting unit 320, 330, 340 terminal 400, 410 communication element 401 queue 402 congestion determining unit 403 congestion occurrence predicting unit 404 inactive determining unit 405 CC
R observation unit 406: congestion notification table 407: EF
CI bit setting unit 420, 430, 440 terminal 500, 510 communication element 501 queue 502 congestion determination unit 503 parameter observation unit 504 CCR observation unit 505 timeout detection unit 506 ACR calculation unit 507 measurement period observation Unit 508 Active connection observing unit 509 Fair allocation calculating unit 511 Congestion notification table 513 EF
CI bit setting unit 520, 530, 540 terminal 600 communication element 601 queue 602 congestion determination unit 603 parameter observation unit 604 CCR observation unit 605 timeout detection unit 606 ACR calculation unit 607 ABR connection number calculation unit 608: Fair allocation calculation unit 609: Congestion notification table 611: EF
CI bit setting section 620, 630, 640 terminal 610 communication element 700, 710 communication element 701 queue 702 congestion determination section 703 active connection determination section 704 fair allocation calculation section 705 measurement period observation section 706 input Cell number calculation unit 707: input cell number comparison unit 708: EF
CI bit setting section 709 ... congestion notification table 720, 73
0,740 terminal 800 communication element 801 queue 802 congestion determination unit 803 ABR connection number calculation unit 804 fair allocation calculation unit 805 measurement period observation unit 806 input cell number calculation unit 807 input cell number comparison unit 808 ... EF
CI bit setting unit 809: congestion notification table 820, 83
0,840 ... Terminal 810 ... Communication element 900,91
0: communication element 901: queue 902: congestion determination unit 903: parameter observation unit 904: CC
R observation unit 905: timeout detection unit 906: AC
R calculation unit 907: Measurement period observation unit 908: AC
R maximum value calculator 909: ACR threshold calculator 911: AC
R comparison unit 912 ... congestion notification table 913 ... EF
CI bit setting unit 920, 930, 940 Terminal 1000, 1010 Communication element 1001 Queue 1002 Congestion determination unit 1003 Input cell number calculation unit 1004 Measurement period observation unit 1005 Input cell number maximum value calculation unit 1006 Input Cell number threshold value calculation unit 1007 ... input cell number comparison unit 1008 ... congestion notification table 1009 ... E
FCI bit setting unit 1020, 1030, 1040 terminal 1100, 1110 communication element 1101 queue 1102 congestion determination unit 1103 parameter observation unit 1104 CCR observation unit 1105 timeout detection unit 1106 ACR calculation unit 1107 measurement period observation Unit 1108 ACR level calculation unit 1109 A
CR level management unit 1111 ... ACR threshold value calculation unit 1112 ... A
CR comparison unit 1113 EFCI bit setting unit 1120, 1130, 1140 Terminal 1200 Communication element 1201 Queue 1202 Congestion determination unit 1203 Input cell number calculation unit 1204 Measurement period observation unit 1205 Cell number level calculation unit 1206 Cell number level management unit 1207 Input cell number threshold value calculation unit 1208 Input cell number comparison unit 1209 Congestion notification table 1211 E
FCI bit setting unit 1220, 1230, 1240 ... terminal 1210 ... communication element

Claims (26)

[Claims] 1. The method according to claim 1, wherein said AT is used in an ATM communication network accommodating one or more connections for transferring information in the form of fixed-length cells using an ABR service category.
When information is transmitted between the transmitting terminal and the receiving terminal by the M communication network, after receiving a cell input to the ATM communication network from the transmitting terminal and performing a predetermined process on the received cell, A communication element for transmitting the cells to the receiving terminal, a queue in which cells transmitted in each of the connections are multiplexed and temporarily stored, and an input permission rate for each of the connections. A congestion prediction unit for predicting whether or not congestion occurs in the queue based on an ACR value; and the ACR held in the transmission terminal when the congestion is predicted by the congestion prediction unit. Congestion notification means for issuing to the transmitting terminal an instruction to reduce the ACR or an instruction to prohibit an increase in the ACR. Element. 2. The ACR calculating means for calculating an ACR value, which is an ACR value for each of the connections, based on information contained in a cell transmitted to each of the connections and arriving at the queue. A total value calculating means for calculating an ACR total value defined as an addition value of the ACR values for all of the connections; a congestion prediction threshold calculated by a predetermined method with the ACR total value; And a comparing unit that compares the ACR total value with the congestion prediction threshold and predicts that congestion will occur in the queue based on a comparison result by the comparing unit. Item 2. The communication element according to Item 1. 3. The congestion predicting means, comprising: after the congestion notifying means issues an instruction to reduce the ACR to the transmitting terminal corresponding to one of the connections, after the input rate of cells to the queue is reduced. FRTT calculating means for calculating, for all of the connections, a rate control delay time which is a delay time until decreasing in response to the instruction; information included in a cell transmitted to each of the connections and arriving at the queue; ACR calculating means for calculating an ACR value that is an ACR value for each of the connections based on the following formulas: defined as an addition value obtained by adding the product of the ACR value and the rate control delay time for all of the connections Predicted value calculating means for calculating a predicted value of the total maximum number of input cells to be calculated; and Comparing means for comparing the measured value with a congestion prediction threshold value calculated by a predetermined method, based on a comparison result by the comparing means, wherein the total maximum input cell number predicted value is the congestion prediction threshold. The communication element according to claim 1, wherein when the value is larger than the value, it is predicted that congestion will occur in the queue. 4. The method according to claim 1, wherein said AT is used in an ATM communication network accommodating one or more connections for transferring information in the form of fixed-length cells using an ABR service category.
When information is transmitted between the transmitting terminal and the receiving terminal by the M communication network, after receiving a cell input to the ATM communication network from the transmitting terminal and performing a predetermined process on the received cell, A communication element for transmitting the cells to the receiving terminal, a queue in which cells transmitted in each of the connections are multiplexed and temporarily stored, and whether or not congestion occurs in the queue. Congestion determination means, and an input rate calculation means for calculating a cell input rate from the transmitting terminal corresponding to each of the connections, based on the number of cells transmitted in each of the connections and arriving at the queue. An input rate for each of the connections, wherein the cell input rate from the transmitting terminal is determined by a predetermined method An input rate determining means for determining whether or not the cell input rate is smaller than a threshold; and if the congestion determining means determines that the congestion occurs, the input rate determining means determines that the cell input rate is equal to the input rate threshold. Congestion notification means for issuing, to the transmitting terminal corresponding to the connection determined to be smaller than the value, an instruction to decrease the ACR for the connection or an instruction to prohibit an increase in the ACR for the connection. Communication element. 5. Based on information contained in a cell transmitted on each of said connections and arriving at said queue,
ACR calculating means for calculating an ACR value that is an ACR value for each of the connections, wherein the input rate determining means uses a value obtained by subtracting a preset constant from the ACR value as the input rate threshold value. The communication element according to claim 4, wherein the communication element is calculated. 6. The congestion judging means, congestion detecting means for detecting congestion in the queue, and whether or not congestion occurs in the queue based on an ACR value which is an input permission rate for each of the connections. Including congestion prediction means for predicting, when the congestion is not detected by the congestion detection means and when the congestion is predicted to occur by the congestion prediction means, the cell input rate by the input rate determination means, Issue to the transmitting terminal corresponding to the connection determined to be smaller than the input rate threshold value, an instruction to decrease the ACR for the connection or an instruction to prohibit an increase in the ACR for the connection. Communication element according to claim 4. 7. The ATM system according to claim 1, wherein said ATM is used in an ATM communication network accommodating one or more connections for transferring information in a fixed-length cell using an ABR service category.
When information is transmitted between the transmitting terminal and the receiving terminal by the M communication network, after receiving a cell input to the ATM communication network from the transmitting terminal and performing a predetermined process on the received cell, A communication element for transmitting the cells to the receiving terminal, a queue in which cells transmitted in each of the connections are multiplexed and temporarily stored, and whether or not congestion occurs in the queue. ACR calculating means for calculating an ACR value, which is an ACR value for each of the connections, based on information contained in cells transmitted to each of the connections and arriving at the queue, Fair allocation calculating means for calculating a fairly allocated bandwidth value by a predetermined method based on the output bandwidth of the queue; and the ACR value Comparing means for comparing the fair share bandwidth value, when the congestion is determined to be generated by said congestion determining means, said A based on the comparison result by the comparison means
Congestion notification means for issuing an instruction to reduce the ACR or an instruction to prohibit an increase in the ACR to the transmitting terminal corresponding to a connection having a CR value larger than the fairly allocated bandwidth value. Communication element. 8. The fair allocation calculation means calculates the number of active connections, which is the number of connections that input cells to the queue, and outputs all cells of all connections using the ABR service from the queue. 8. The fairly allocated bandwidth value is calculated by dividing an ABR service transmission rate, which is a rate to be performed, by the number of active connections.
Communication element according to. 9. The fair allocation calculating means obtains the number of ABR connections, which is the number of connections using the ABR service among the connections set on the queue, and calculates all the connections using the ABR service. The communication element according to claim 7, wherein the fairly allocated bandwidth value is calculated by dividing an ABR service transmission rate, which is a rate at which cells are output from the queue, by the number of ABR connections. 10. The ATM network according to claim 1, wherein said ATM network is used in an ATM communication network accommodating one or more connections for transferring information in a fixed-length cell using an ABR service category.
When information is transmitted between the transmitting terminal and the receiving terminal by the TM communication network, after receiving a cell input to the ATM communication network from the transmitting terminal and performing a predetermined process on the received cell, A communication element for transmitting the cells to the receiving terminal, a queue in which cells transmitted in each of the connections are multiplexed and temporarily stored, and whether or not congestion occurs in the queue. Congestion determination means, and an input rate calculation means for calculating a cell input rate from the transmitting terminal corresponding to each of the connections, based on the number of cells transmitted in each of the connections and arriving at the queue. A fair allocation calculating means for calculating a fairly allocated bandwidth value by a predetermined method based on the output bandwidth of the queue; Input rate determining means for determining whether the cell input rate from the transmitting terminal corresponding to each of the actions is greater than the fairly allocated bandwidth value, and when the congestion determining means determines that the congestion occurs. An instruction to reduce an ACR which is an input permission rate for a connection in which the cell input rate is greater than the fairly allocated bandwidth value or an instruction to prohibit an increase in the ACR for the connection, based on a determination result by the input rate determination means. And a congestion notification unit for issuing to the transmission terminal corresponding to the connection. 11. The fair allocation calculating means calculates the number of active connections, which is the number of connections that input cells to the queue, and outputs all cells of all connections using the ABR service from the queue. The communication element according to claim 10, wherein the fairly allocated bandwidth value is calculated by dividing an ABR service transmission rate, which is a rate to be performed, by the number of active connections. 12. The fair allocation calculating means obtains the number of ABR connections which is the number of connections using the ABR service among the connections set on the queue, and calculates all the connections using the ABR service. The communication element according to claim 10, wherein the fairly allocated bandwidth value is calculated by dividing an ABR service transmission rate, which is a rate at which cells are output from the queue, by the number of ABR connections. 13. An ATM network for use in an ATM communication network accommodating one or more connections for transferring information in the form of fixed length cells using the ABR service category.
When information is transmitted between the transmitting terminal and the receiving terminal by the TM communication network, after receiving a cell input to the ATM communication network from the transmitting terminal and performing a predetermined process on the received cell, A communication element for transmitting the cells to the receiving terminal, a queue in which cells transmitted in each of the connections are multiplexed and temporarily stored, and whether or not congestion occurs in the queue. ACR calculating means for calculating an ACR value, which is an ACR value for each of the connections, based on information contained in cells transmitted to each of the connections and arriving at the queue, ACR maximum value calculating means for obtaining an ACR maximum value which is a maximum value of the ACR values for each of the connections; Said ACR values for each transfection,
ACR comparing an ACR threshold defined as a value obtained by subtracting a predetermined constant value from the ACR maximum value.
Comparing means, when the congestion determining means determines that the congestion occurs, based on the comparison result by the ACR comparing means, the ACR value to the transmitting terminal corresponding to the connection greater than the ACR threshold On the other hand, the ACR
And a congestion notification means for issuing an instruction to reduce the ACR or an instruction to prohibit the increase of the ACR. 14. The method according to claim 1, wherein said A is used in an ATM communication network accommodating one or more connections for transferring information in the form of fixed-length cells using the ABR service category.
When information is transmitted between the transmitting terminal and the receiving terminal by the TM communication network, after receiving a cell input to the ATM communication network from the transmitting terminal and performing a predetermined process on the received cell, A communication element for transmitting the cells to the receiving terminal, a queue in which cells transmitted in each of the connections are multiplexed and temporarily stored, and whether or not congestion occurs in the queue. Congestion determination means, and an input rate calculation means for calculating a cell input rate from the transmitting terminal corresponding to each of the connections, based on the number of cells transmitted in each of the connections and arriving at the queue. Input rate maximum value calculation for obtaining an input rate maximum value which is a maximum value of the cell input rates for each of the connections. Output means, and the cell input rate for each of the connections, and input rate comparing means for comparing an input rate threshold defined as a value obtained by subtracting a predetermined constant value from the input rate maximum value, When the congestion determining means determines that the congestion occurs, the ACR is an input permission rate for a connection in which the cell input rate value is larger than the input rate threshold value, based on a comparison result by the input rate comparing means. Congestion notification means for issuing an instruction to reduce the ACR or an instruction to prohibit an increase in the ACR for the connection to the transmitting terminal corresponding to the connection;
A communication element comprising: 15. One or more ABs that transfer information in fixed-length cells using ABR service categories
R is used in an ATM communication network accommodating an R service connection, and when information is transmitted between a transmitting terminal and a receiving terminal by the ATM communication network, the AT is transmitted from the transmitting terminal to the AT.
A communication element for receiving a cell input to the M communication network, performing predetermined processing on the received cell, and then transmitting the cell to the receiving terminal, wherein the communication element transmits the cell through each of the ABR service connections. Cells to be multiplexed and temporarily stored, congestion determining means for determining whether or not congestion occurs in the queue, and transmitted in each of the ABR service connections to arrive in the queue Based on the information contained in the cell,
A for each of the ABR service connections
ACR calculating means for calculating a CR value Vacr; T (i1) for integers i1 and i2 such that i1 <i2
Level thresholds T (0), T (1), which are n constants preset to satisfy the relationship <T (i2)
.., T (n−1) based on an integer i such that 0 ≦ i ≦ n−1
On the other hand, when it is assumed that the ACR value for the connection of the ABR service connection in which the ACR value Vacr is larger than the level threshold value T (i) is equal to the level threshold value T (i). A virtual ACR total value calculating means for calculating a total value of ACR values of the ABR service connection as a virtual ACR total value TACR (i), and a predetermined input rate target value Tg_Rin,
If CR (0)> Tg_Rin, select all the ABR service connections, and TACR (j)> Tg_R
If there is an integer j satisfying 1 ≦ j ≦ n−1 that satisfies in ≧ TACR (j−1), TACR (j)> Tg_Rin ≧ T
A is smaller than the level threshold T (j-1) corresponding to an integer smaller by 1 than the integer j that satisfies ACR (j-1).
A connection having a large CR value Vacr is selected from the ABR service connections, and TACR (j)>
If there is no integer j that satisfies Tg_Rin, a connection selecting means for selecting a connection having the ACR value Vacr greater than a level threshold value T (n-1) from the ABR service connections; When it is determined that the congestion occurs, the transmission terminal corresponding to the connection selected by the connection selection means is instructed to decrease the ACR for the selected connection or the increase of the ACR for the connection is prohibited. And a congestion notification means for issuing an instruction to perform the communication. 16. The virtual ACR total value calculating means, wherein the level threshold values T (0), T (1),.
A variable C (i) defined for an integer i such that 0 ≦ i ≦ n based on 1), and when i = 0, satisfies the relationship Vacr ≦ T (0) among the ABR service connections. Defined as the number of connections, 1 ≦ i ≦ n
-1 when T of the ABR service connection
(I-1) is defined as the number of connections satisfying the relationship of Vacr ≦ T (i).
Of the BR service connections, Vacr> T (n-
1) a first calculating means for calculating a variable C (i) defined as the number of connections satisfying the relationship: and a total number of levels N (j) defined for an integer j such that 0 ≦ j ≦ n. A second calculating means for calculating a total number of levels N (j) defined as an added value obtained by adding C (i) to all integers i satisfying j ≦ i ≦ n, 0 ≦ A threshold calculation parameter CTh (j) defined for an integer j satisfying j ≦ n−1, and when i = 0, is calculated by T (0) × N (0) and 1 ≦ i ≦ n When −1, the value is obtained by adding the value V (i) calculated by {T (i) −T (i−1)} × N (i) for all integers i satisfying 0 ≦ i ≦ j. A threshold calculation parameter CTh (j) defined as an addition value is defined as the virtual ACR total value TACR (j). And a third calculation means for calculating, the connection selection means is defined on the basis of 0 ≦ j ≦ n-1 becomes the threshold value calculation parameter CTh defined for integer j (j) A
This is a CR threshold, defined as “0” when CTh (0)> Tg_Rin with respect to a preset input rate target value Tg_Rin, and 1 ≦ j ≦ n satisfying CTh (j)> Tg_Rin. CT if there is an integer j of -1
A level threshold T (jt-j) corresponding to an integer smaller by 1 than the minimum value jt of the integer j satisfying h (j)> Tg_Rin.
ACR threshold calculating means for calculating an ACR threshold defined as T (n-1) when there is no integer j satisfying CTh (j)> Tg_Rin defined as 1), and the ABR service. ACR comparing means for comparing the ACR value Vacr and the ACR threshold value for each of the connections, and based on the comparison result by the ACR comparing means,
A connection in which the value Vacr of R is larger than the ACR threshold is selected from among the ABR service connections. The congestion notifying means selects the connection when the congestion determining means determines that the congestion occurs. Means for the transmitting terminal corresponding to the connection selected by the
The communication element according to claim 15, further comprising: congestion notification means for issuing an instruction to decrease a CR or an instruction to prohibit an increase in the ACR for the connection. 17. One or more ABs that transfer information in fixed-length cells using ABR service categories
R is used in an ATM communication network accommodating an R service connection, and when information is transmitted between a transmitting terminal and a receiving terminal by the ATM communication network, the AT is transmitted from the transmitting terminal to the AT.
A communication element for receiving a cell input to the M communication network, performing a predetermined process on the received cell, and transmitting the cell to the receiving terminal, wherein the communication element transmits the cell through each of the ABR service connections. Queues in which cells to be transmitted are multiplexed and temporarily stored; congestion determination means for determining whether or not congestion occurs in the queues; and transmitted in each of the ABR service connections to arrive in the queues. Input rate calculating means for calculating an input rate Rcin of a cell from the transmitting terminal corresponding to each of the connections based on the number of cells, and T (i1) for integers i1 and i2 such that i1 <i2.
Level thresholds T (0), T (1), which are n constants preset to satisfy the relationship <T (i2)
.., T (n−1) based on an integer i such that 0 ≦ i ≦ n−1
On the other hand, when it is assumed that the input rate of the cell for the connection of the ABR service connection in which the input rate Rcin is larger than the level threshold T (i) is equal to the level threshold T (i). AB
Virtual input rate total value calculating means for calculating the total value of the input rates of the cells for the R service connection as a virtual input rate total value TRcin (i); and for a predetermined input rate target value Tg_Rin, TR
When cin (0)> Tg_Rin, all the ABR service connections are selected, and TRcin (j)> Tg_Rin
1 ≦ j ≦ n−1 that satisfies g_Rin ≧ TRcin (j−1)
If there is an integer j such that TRcin (j)> Tg
A connection having an input rate Rcin greater than a level threshold T (j-1) corresponding to an integer smaller by 1 than an integer j satisfying _Rin ≧ TRcin (j-1) is selected from the ABR service connections; , TRc
connection selection means for selecting, from the ABR service connections, a connection having the input rate Rcin higher than a level threshold T (n-1) when there is no integer j satisfying in (j)>Tg_Rin; When the congestion determination unit determines that the congestion occurs, the ACR which is an input permission rate for the selected connection to the transmitting terminal corresponding to the connection selected by the connection selection unit.
Instructions to reduce or ACR for the connection
And a congestion notification means for issuing an instruction to prohibit an increase in communication. 18. The virtual input total value calculating means, wherein the level threshold values T (0), T (1),.
A variable C (i) defined for an integer i satisfying 0 ≦ i ≦ n based on 1), and when i = 0, the relationship of Rcin ≦ T (0) among the ABR service connections is satisfied. Defined as the number of connections, 1 ≦ i ≦ n
-1 when T of the ABR service connection
(I-1) is defined as the number of connections satisfying the relationship of Rcin ≦ T (i).
Among the BR service connections, Rcin> T (n−
1) a first calculating means for calculating a variable C (i) defined as the number of connections satisfying the relationship: and a total number of levels N (j) defined for an integer j such that 0 ≦ j ≦ n. A second calculating means for calculating a total number of levels N (j) defined as an added value obtained by adding C (i) to all integers i satisfying j ≦ i ≦ n, 0 ≦ A threshold calculation parameter CTh (j) defined for an integer j satisfying j ≦ n−1, and when i = 0, is calculated by T (0) × N (0) and 1 ≦ i ≦ n When −1, the value is obtained by adding the value V (i) calculated by {T (i) −T (i−1)} × N (i) for all integers i satisfying 0 ≦ i ≦ j. The threshold value calculation parameter CTh (j) defined as an addition value is calculated by using the virtual input rate total value TRcin (j). And a third calculating means for calculating an input rate defined based on the threshold calculation parameter CTh (j) defined for an integer j such that 0 ≦ j ≦ n−1. This is a threshold, and is defined as “0” when CTh (0)> Tg_Rin with respect to a preset input rate target value Tg_Rin, and CTh (j)> Tg_Rin
When there is an integer j satisfying 1 ≦ j ≦ n−1, a level threshold T (j) corresponding to an integer smaller by 1 than the minimum value jt of the integer j satisfying CTh (j)> Tg_Rin
input rate threshold value calculation means for calculating an input rate threshold value defined as T (n-1) when there is no integer j defined as t (j-1) and CTh (j)>Tg_Rin; And an input rate comparison means for comparing the input rate Rcin and the input rate threshold value for each of the ABR service connections, based on a comparison result by the input rate comparison means, wherein the input rate Rcin is equal to the input rate. Selecting a connection larger than a threshold value from the ABR service connections, the congestion notifying unit, when the congestion determining unit determines that the congestion occurs, the connection selected by the connection selecting unit The A for the selected connection to the corresponding transmitting terminal
The communication element according to claim 17, further comprising: a congestion notification unit that issues an instruction to decrease a CR or an instruction to prohibit an increase in the ACR for the connection. 19. When information is transmitted between a sending terminal and a receiving terminal by an ATM communication network accommodating one or more connections for transferring information in the form of fixed-length cells using an ABR service category. A flow control method performed between a communication element included in the ATM communication network and the transmitting terminal and the receiving terminal, wherein cells transmitted in each of the connections are multiplexed and temporarily A congestion prediction step of predicting whether or not congestion occurs in the queue to be stored, based on the value of ACR which is an input permission rate for each of the connections; and when the occurrence of congestion is predicted in the congestion prediction step. The ACR held in the transmitting terminal
A congestion notification step of issuing from the communication element including the queue to the transmitting terminal an instruction to decrease the ACR or an instruction to prohibit an increase in the ACR. 20. When information is transmitted between a transmitting terminal and a receiving terminal over an ATM communication network accommodating one or more connections for transferring information in the form of fixed-length cells using the ABR service category. A flow control method performed between a communication element included in the ATM communication network and the transmitting terminal and the receiving terminal, wherein cells transmitted in each of the connections are multiplexed and temporarily A congestion determination step of determining whether or not congestion occurs in the queue to be stored; and, based on the number of cells transmitted to each of the connections and arriving at the queue, from the transmitting terminal corresponding to each of the connections. An input rate calculating step of calculating a cell input rate of the connection; Input rate, the input rate determination step to determine whether or not smaller than the input rate threshold determined by a predetermined method, and when it is determined that the congestion occurs in the congestion determination step, In the input rate determining step, the transmitting terminal corresponding to the connection whose cell input rate is determined to be smaller than the input rate threshold is instructed to decrease the ACR for the connection or increase the ACR for the connection. A congestion notification step of issuing a prohibition instruction. 21. When information is transmitted between a transmitting terminal and a receiving terminal by an ATM communication network accommodating one or more connections for transferring information in the form of fixed-length cells using the ABR service category. A flow control method performed between a communication element included in the ATM communication network and the transmitting terminal and the receiving terminal, wherein cells transmitted in each of the connections are multiplexed and temporarily A congestion determining step of determining whether or not congestion occurs in the queue to be stored; and, based on information contained in a cell transmitted to each of the connections and arriving at the queue, an ACR value for each of the connections is used. An ACR calculating step of calculating a certain ACR value; and a fairly dividing by a predetermined method based on an output band of the queue. A fair allocation calculating step of calculating a hit bandwidth value; a comparing step of comparing the ACR value with the fairly allocated bandwidth value; A congestion notification step of issuing an instruction to decrease the ACR or an instruction to prohibit an increase in the ACR to the transmitting terminal corresponding to a connection in which the ACR value is larger than the fairly allocated bandwidth value based on a result. A flow control method, characterized in that: 22. When information is transmitted between a sending terminal and a receiving terminal over an ATM communication network accommodating one or more connections for transferring information in the form of fixed length cells using the ABR service category. A flow control method performed between a communication element included in the ATM communication network and the transmitting terminal and the receiving terminal, wherein cells transmitted in each of the connections are multiplexed and temporarily A congestion determining step of determining whether or not congestion occurs in the queue to be stored; and the transmitting terminal corresponding to each of the connections based on the number of cells transmitted in each of the connections and arriving at the queue. An input rate calculating step of calculating a cell input rate from a cell, and fairness is determined by a predetermined method based on an output band of the queue. A fair allocation calculating step of calculating an allocated bandwidth value; an input rate determining step of determining whether the cell input rate from the transmitting terminal corresponding to each of the connections is higher than the fair allocated bandwidth value; When it is determined in the congestion determination step that the congestion occurs, the ACR that is an input permission rate for a connection in which the cell input rate is greater than the fairly allocated bandwidth value is reduced based on the determination result in the input rate determination step. A congestion notification step of issuing an instruction or an instruction to prohibit an increase in the ACR for the connection to the transmitting terminal corresponding to the connection. 23. When information is transmitted between a sending terminal and a receiving terminal over an ATM communication network accommodating one or more connections for transferring information in the form of fixed-length cells using the ABR service category. A flow control method performed between a communication element included in the ATM communication network and the transmitting terminal and the receiving terminal, wherein cells transmitted in each of the connections are multiplexed and temporarily A congestion determining step of determining whether or not congestion occurs in the queue to be stored; and an ACR value for each of the connections based on information contained in cells transmitted to each of the connections and arriving at the queue. An ACR calculating step of calculating an ACR value that is a maximum value of the ACR values for each of the connections. Calculating an ACR maximum value for obtaining a certain ACR maximum value; the ACR value for each of the connections;
ACR comparing an ACR threshold defined as a value obtained by subtracting a predetermined constant value from the ACR maximum value.
A comparison step, and when it is determined that the congestion occurs in the congestion determination step, based on a comparison result in the ACR comparison step, the ACR value corresponds to the transmission terminal corresponding to a connection greater than the ACR threshold. On the other hand,
A congestion notification step of issuing an instruction to reduce the ACR or an instruction to prohibit the increase of the ACR. 24. When information is transmitted between a transmitting terminal and a receiving terminal over an ATM communication network accommodating one or more connections for transferring information in the form of fixed-length cells using the ABR service category. A flow control method performed between a communication element included in the ATM communication network and the transmitting terminal and the receiving terminal, wherein cells transmitted in each of the connections are multiplexed and temporarily A congestion determination step of determining whether or not congestion occurs in the queue to be stored; and, based on the number of cells transmitted in each of the connections and arriving in the queue, from the transmitting terminal corresponding to each of the connections. An input rate calculating step of calculating a cell input rate of the connection; An input rate maximum value calculating step for obtaining an input rate maximum value that is a maximum value of the cell rate; a cell input rate for each of the connections; and a value obtained by subtracting a predetermined constant value from the input rate maximum value. An input rate comparing step of comparing an input rate threshold value with the input rate threshold value; and, when it is determined in the congestion determining step that the congestion occurs, the input rate value is determined based on a comparison result in the input rate comparing step. A congestion notification step of issuing to the transmitting terminal corresponding to the connection an instruction to decrease the ACR, which is an input permission rate for a connection greater than a threshold value, or to prohibit an increase in the ACR for the connection. A method of flow control, comprising: 25. When information is transmitted between a sending terminal and a receiving terminal over an ATM communication network accommodating one or more connections for transferring information in the form of fixed-length cells using the ABR service category. A flow control method performed between a communication element included in the ATM communication network and the transmitting terminal and the receiving terminal, wherein cells transmitted in each of the connections are multiplexed and temporarily A congestion determination step of determining whether or not congestion occurs in the queue to be stored; and based on information contained in a cell that arrives at the queue after being transmitted in each of the ABR service connections,
A for each of the ABR service connections
An ACR calculation step of calculating a CR value Vacr; and T (i1) for integers i1 and i2 such that i1 <i2.
Level thresholds T (0), T (1), which are n constants preset to satisfy the relationship <T (i2)
.., T (n−1) based on an integer i such that 0 ≦ i ≦ n−1
On the other hand, if the ACR value of the ABR service connection is assumed to be equal to the level threshold T (i) for a connection in which the ACR value Vacr is greater than the level threshold T (i). A virtual ACR total value calculating step of calculating the total value of the ACR values of the ABR service connection as a virtual ACR total value TACR (i), and a TA input value target value Tg_Rin which is set in advance.
If CR (0)> Tg_Rin, select all the ABR service connections, and TACR (j)> Tg_R
If there is an integer j satisfying 1 ≦ j ≦ n−1 that satisfies in ≧ TACR (j−1), TACR (j)> Tg_Rin ≧ T
A is smaller than the level threshold T (j-1) corresponding to an integer smaller by 1 than the integer j that satisfies ACR (j-1).
A connection having a large CR value Vacr is selected from the ABR service connections, and TACR (j)>
If there is no integer j satisfying Tg_Rin, a connection selecting step of selecting from the ABR service connections a connection in which the ACR value Vacr is greater than a level threshold value T (n-1); In step (a), when it is determined that the congestion occurs, an instruction to decrease the ACR for the selected connection or an increase in the ACR for the connection to the transmitting terminal corresponding to the connection selected in the connection selection step is prohibited. A congestion notification step of issuing an instruction to perform the flow control. 26. When information is transmitted between a sending terminal and a receiving terminal over an ATM communication network accommodating one or more connections for transferring information in the form of fixed-length cells using the ABR service category. A flow control method performed between a communication element included in the ATM communication network and the transmitting terminal and the receiving terminal, wherein cells transmitted in each of the connections are multiplexed and temporarily A congestion determining step of determining whether or not congestion occurs in the queue to be stored; and the transmission corresponding to each of the ABR service connections based on the number of cells transmitted in each of the ABR service connections and arriving at the queue. An input rate calculating step of calculating an input rate Rcin of a cell from the terminal; On the other hand, T (i1)
Level thresholds T (0), T (1), which are n constants preset to satisfy the relationship <T (i2)
.., T (n−1) based on an integer i such that 0 ≦ i ≦ n−1
On the other hand, when it is assumed that the input rate of the cell for the connection of the ABR service connection in which the input rate Rcin is larger than the level threshold T (i) is equal to the level threshold T (i). AB
A virtual input rate total value calculating step of calculating the total value of the input rates of the cells for the R service connection as a virtual input rate total value TRcin (i); and, for a preset input rate target value Tg_Rin, TR
When cin (0)> Tg_Rin, all the ABR service connections are selected, and TRcin (j)> Tg_Rin
1 ≦ j ≦ n−1 that satisfies g_Rin ≧ TRcin (j−1)
If there is an integer j such that TRcin (j)> Tg
A connection having an input rate Rcin greater than a level threshold T (j-1) corresponding to an integer smaller by 1 than an integer j satisfying _Rin ≧ TRcin (j-1) is selected from the ABR service connections; , TRc
if there is no integer j satisfying in (j)> Tg_Rin, a connection selecting step of selecting a connection having the input rate Rcin higher than a level threshold T (n-1) from the ABR service connections; When the congestion is determined to occur in the congestion determination step, an instruction to the transmission terminal corresponding to the connection selected in the connection selection step to reduce the ACR that is an input permission rate for the selected connection. Or a congestion notification step of issuing an instruction to prohibit an increase in the ACR for the connection.