JP2002094514A - Fluctuating delay suppression control method and system in asynchronous transfer mode network - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fluctuating delay suppression control method and system in an asynchronous transfer mode network by which a required time between terminals is suppressed in the order of 10 microseconds in the case of utilizing an ATM network by using a general-purpose device in the ATM network without the need for any special revamping. SOLUTION: Each of the terminals is provided with a cell transmission function 36 that can transmit an ATM cell to monitor the state of the ATM network, a retrieval function 37 that receives the ATM cell, retrieves data transmission timing to bring congestion to a desirably specified value or below when the ATM cell includes congestion information and transmits the timing of the retrieval result, and a timing adjustment function 38 that adjusts the transmission timing of the ATM cell when the received ATM cell includes the timing information and transmits the adjusted transmission timing again.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for controlling communication quality between terminals connected to an asynchronous transfer mode network. The present invention relates to a method and a system capable of suppressing the above problem.

[0002]

2. Description of the Related Art Conventionally, an asynchronous transfer mode (ATM; Asyn
chronous Transfer Mode) is not only continuous information like telephone, but also burst information like data communication.
It is known as a communication method in which a cell is divided into information units called cells, transferred and exchanged at a very high speed, and the receiving side returns the original information. In such an ATM, congestion or the like may occur when cells are concentrated at a specific timing of a specific line, and a cell delay time may occur.

The conventional method for guaranteeing the delay time fluctuation in the ATM network is generally performed in the following procedure. First, call admission control (CAC)
When performing the transmission, the transmission quality (QoS; Qual
the service class to be used in accordance with the service class. The CAC determines whether this service can be provided by the ATM network, and if it determines that the service can be provided, connects to the ATM network with the service class requested by the user. AT
Among the types of service classes provided in the M network, the classes related to the delay time and the delay time variation related to the present invention are CBR and VBR. Here, the delay time guaranteed by the VBR is longer than that provided by the CBR, and therefore, only the CBR will be described below.

[0004] CBR is a class that has the highest priority at the time of transmission, and is the class that guarantees QoS strictly among ATMs. When the user uses the service class CBR, the following two traffic parameters are declared to the ATM network side. PCR (Peak Cell Rate) and CDVT (Cell Dela
y Variation Tolerance).

[0005] The PCR indicates the upper limit of the transmission rate that can be transmitted on the ATM connection, and is defined by the reciprocal of the minimum input interval T between cells. PCR
Is defined by successive cell intervals T, but CDV
T indicates a UNI (User Network) after the terminal generates a cell.
k Interface: an interface between the user and the network) to which extent the cell transfer interval T is allowed to vary. This delay variation is caused by the overhead of the physical layer and the interposition of the multiplexing device in the UNI. The CBR class is
The bandwidth is allocated to the user by PCP based on the user's declaration. As reported by the user, a delay time only occurs between lines of the same CBR class in order to flow data in a band lower than the PCR. The QoS control is actually performed by the ATM switch based on the parameters declared by the user.

FIG. 9 is a block diagram showing some functions of the ATM exchange. In the ATM switch 100 shown in FIG. 9, a high-priority CBR input buffer 200H, a low-priority VBR input buffer 200L, a high-priority CBR output buffer 300H, a low-priority VBR output buffer 300L, A switch unit 400 interposed between them for switching the data of the input buffer to the output buffer is provided.

The high-priority CBR input buffer 20
0H, a low-priority VBR input buffer 200L, a high-priority CBR output buffer 300H, and a low-priority VB.
The R output buffer 300L is connected to ports 1 and
.., N.

In general, when a cell is sent from a connection connected by a user to the ATM switch 100 and a connection to the CBR is declared, an input buffer for the CBR corresponding to the service class is used. Stored at 200H.

[0009] The CBR class has the highest priority and is replaced without being affected by VBR or other classes. In addition, VBR has a higher priority set than other service classes ABR and UBR.
Even if BR and UBR classes are mixed, it is not affected. CB
The R class allocates a band to the user by PCR based on the user's declaration.

FIG. 10 shows the configuration of a CBR input buffer for explaining the threshold value of the input buffer. CBR
In the input buffer 200H, as shown in FIG. 10, some thresholds are provided, and CLP (Cell
If “Loss Priority: cell discard priority bit” is “1”, if the number of cells already stored in the input buffer 200H exceeds the threshold value CLP provided in the input buffer 200H, the service is stopped. The connection from the user is rejected by the CAC because it cannot be guaranteed.

Although the use of the CLP can be expected to reduce the delay time, generally, the delay time is reduced according to the performance of the exchange.
The setting is about 0 cells, and the user cannot change the setting. Further, even if the CLP is changed to a low value, there is a high possibility that the connection will be rejected by the CAC. Also, output conflicts described later cannot be avoided.

If it is the first cell among the cells stored in the input buffer 200H, it is switched by the switch unit 400 and is replaced with a port of the CBR output buffer 300H corresponding to a desired output line. At this time, if there are a plurality of CBR lines and the same output port is aimed, it is necessary to determine from which input buffer 200H the input buffer 200H should be replaced.

Since the priorities are the same among the CBR classes, a method called round robin is generally employed. This method called round robin is a method of simply selecting and exchanging ports 1 to n in order. In this method, the output buffer 300H outputs to the output line in a predetermined transmission band in order from the head cell. Therefore, when cells compete for the same output port, the cells are kept waiting in the input buffer 200H by the number of output lines competing in the worst case. This is a problem called output conflict.

As described above, in the conventional method, the delay time is guaranteed by giving priority classes and prioritizing transmission and switching of the higher priority class. Fine control of the order is not possible.

[0015]

The main cause of the delay variation in the ATM exchange is that the same output port (or the same virtual path (VC)) comes from different input paths.
This is the case.

FIG. 11 shows what happens when different input paths are aimed at the same output port. In FIG. 11, reference numerals 500a, 500b, and 500c denote terminals, reference numeral 100 denotes an ATM switch, and reference numerals 600a,
600b and 600c are input lines, and 700 is an output line.

As can be understood from FIG. 11, when output competition occurs and maximum delay time fluctuation occurs, the transmitting terminals 500a, 500b and 500c transmit information Ia, Ib and Ic at the same time t ₁ and t _6. However, this is a case where the same output port (output line 700) is aimed. Such an input line 6
When a plurality of 00a, 600b, and 600c are multiplexed, a delay time is generated for one exchange 100 by the amount of the line. That is, in the output line 700,
The information Ia is switched at times t ₁₁ and t ₁₆ and has no delay, but the information Ib is switched at times t ₁₂ and t ₁₇ and is delayed, and the information Ic is switched at times t ₁₃ and t _18. This will result in further delays.

In designing a network, the worst case must be taken into consideration. Therefore, if the QoS condition of the delay time or the delay time variation is to be set to 10 micro-orders, it cannot be accommodated by more than ten lines. there were.

The present invention avoids output contention, provides a delay time,
An object of the present invention is to provide a delay fluctuation suppression control method and system in an asynchronous transfer mode network that suppresses delay time fluctuation and improves the PCR value of the CBR service with the average transmission speed of CR information. That is, according to the present invention, when using the ATM network, the QoS conditions between terminals are suppressed to the order of 10 microseconds, and the ATM network uses general-purpose equipment and realizes the control without special modification. Is to do.

[0020]

In order to achieve this object, the present invention provides a CBR (Constaurate) which occurs in an ATM switch.
(nt Bit Rate) In order to avoid cell contention between traffics and to avoid special modification of the ATM network, means for adjusting the transmission timing between terminals are provided.

That is, the method for controlling delay fluctuation suppression in an asynchronous transfer mode network according to the present invention can guarantee the transmission quality control of the asynchronous transfer mode technology when performing communication between terminals connected to the asynchronous transfer mode network. In a method in which the delay time between terminals that do not exist can be suppressed to an allowable value or less, one terminal transmits a cell for monitoring the state of the asynchronous transfer mode network to the other terminal by a cell transmission function and receives this cell. The other terminal, when there is congestion information in the cell by the search function, searches for a data transmission timing that is equal to or less than a desired specified value, transmits the timing of the search result to one terminal, and the one terminal When the cell received by the timing adjustment function has timing information, the transmission timing of the cell is adjusted and transmitted again. Further, the delay fluctuation suppression control system in the asynchronous transfer mode network according to the present invention, when performing communication between terminals connected to the asynchronous transfer mode network, between the terminals that can not be guaranteed by the transmission quality control of the asynchronous transfer mode technology In a system that can suppress the delay time of the terminal to an allowable value or less, the two terminals have a cell transmission function that can transmit a cell that monitors the state of the asynchronous transfer mode network, A search function for searching for a data transmission timing that is equal to or less than a desired specified value and transmitting the timing of the search result, and when a received cell has timing information, adjust the transmission timing of the cell and retransmit. Each has a timing adjustment function.

Accordingly, when congestion occurs when an ATM cell passes through the ATM exchange, the EFCI changes to 1
Pay attention to the (Explicit Forward Congestion Indication) bit, set the EFCI threshold value to the maximum value of the allowable delay variation in the exchange, and if there is a cell with the EFCI bit of 1, realize the delay variation suppression control method in the asynchronous transfer mode network. Protocol TAP (Timing Adjustment Proto
The transmission timing is adjusted by mapping it to the congestion information of the col) section and feeding it back to the transmission source. As a result, TA
P adjusts the timing of cell transmission to avoid cell contention and suppress delay time fluctuation. By adjusting the transmission timing in this way, a cell from another source can be inserted into the cell interval, and a network can be designed without creating a useless free band. Protocol TA
The P satisfies the QoS requirement for the application by adjusting the transmission timing and eliminating the fluctuation of the delay time, and can accommodate the channel.

The search function in the delay fluctuation suppression control method and system in the asynchronous transfer mode network according to the present invention has a function of randomly searching for a timing that is equal to or less than a desired delay time, or a terminal having the delay time as information, It is characterized in that it has a function of searching for a timing at which it is equal to or less than a prescribed value.

[0024]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an ATM network including an apparatus for implementing a delay fluctuation suppression control method in an asynchronous transfer mode network according to an embodiment of the present invention.

In FIG. 1, terminals 1 A and 1 B provided in two power station premises are connected via an ATM network 2. The terminal 1A is an information transmitting terminal 3A,
CLAD (Cell Assemble / Deassemble) 4A. The terminal 1B includes an information transmitting terminal 3B and a CLAD 4B.
As described above, the term “terminal 1A” is a concept that includes both the information transmitting terminal device 3A and the CLAD 4A.
When the terminal 1B is referred to, the information transmitting terminal device 3B and the CL
This is a concept that includes both AD4B and AD4B.

The information transmitting terminal 3A has a CLAD 4A
Is connected to the ATM network 2 via the. The information transmitting terminal device 3B is connected to the ATM network 2 via the CLAD 4B.

The information transmitting terminal devices 3A and 3B include an arithmetic processing unit (CPU), a main storage device, a ROM, an input / output port, a large-capacity storage device such as a hard disk, an input / output device, and the like.

The CLADs 4A and 4B are the information transmitting terminals 3
A, 3B and the interface between the ATM network 2;
Each has a function of implementing the delay variation suppression control method in the asynchronous transfer mode network according to the embodiment of the present invention.

The ATM network 2 has ATM lines 21,.
, And ATM exchanges 22,..., 22.

FIG. 2A shows a function for realizing the delay fluctuation suppression control method in the asynchronous transfer mode network of the present invention provided in the CLAD. FIG. 2B shows a specific example of a function for realizing the delay variation suppression control method in the asynchronous transfer mode network of the present invention. FIG. 3 shows an ATM used in the delay fluctuation suppression control method in the asynchronous transfer mode network according to the present invention.
1 shows the structure of a cell.

In FIG. 2A, CLAD4A and C
LAD4B includes a protocol TAP (Timing Adjuvant) that implements a delay fluctuation suppression control method in an asynchronous transfer mode network.
stment Protocol) 30. This TAP30
The application program 32 of the protocol stack 31 of the CLADs 3A and 3B and the AAL (ATM Adapti
on Layer) 33 so that the AAL 33 and the application program 32 can be mediated. Note that an ATM layer 34 is provided below the AAL 33, and a physical layer 35 is provided below the ATM layer 34.

As shown in FIG. 3, the ATM cell 40 comprises an ATM cell header 41, a TAP section 42, and a power information section 43. Further, the TAP unit 42 has at least network congestion information 42a and timing adjustment control 42b. The configuration of the ATM cell 40 is described in detail in Table 1 below.

Here, the ATM cells are stored in the ATM switch 22,
, 22 when the congestion occurs, the EFCI (Explicit Forward Congestion Indicat
), the EFCI threshold is set to the maximum value of the allowable delay variation in the ATM exchanges 22,.
If there is a cell whose EFCI bit is “1”, the TAP unit 42
To the congestion information 42a of the transmission source CLAD3
It has the function of feeding back to A and adjusting the transmission timing.

In FIG. 2A, the CL constituting the terminal
AD4A, 4B, when performing communication between terminals connected to an asynchronous transfer mode network, a method capable of suppressing a delay time between terminals, which cannot be guaranteed by transmission quality control of the asynchronous transfer mode technology, to a desired specified value or less. It has a function that can realize.

That is, the CLADs constituting both terminals
4A and 4B monitor the status of the asynchronous transfer mode network.
A cell transmission function 36 capable of transmitting the TM cell 40;
Upon receiving the TM cell 40, the TAP section 4 of the ATM cell 40
When there is congestion information in the second congestion information 42a, a data transmission timing that is less than a desired prescribed value is searched, and the timing of the search result is transmitted to the timing adjustment control 42b of the TAP unit 42 of the ATM cell 40 and transmitted. Search function 3
7 and a timing adjustment function 38 for adjusting the transmission timing of the ATM cell 40 and transmitting the same again when there is timing information in the timing adjustment control 42b of the TAP section 42 of the received ATM cell 40.

Further, CLAD4A constituting the above terminal,
4B has a data transmission timing search function 37,
A random timing search function that randomly searches for a timing that is equal to or less than a desired delay time, or a table reference timing search function that has a delay time as information in the CLADs 3A and 3B and searches for a timing that is equal to or less than a specified value. .

Next, a protocol format required for the operation of the TAP 30 will be described in detail. In this format, in addition to the TAP control information used in the operation of the TAP 30, the TAP 30 is sent together with the application program 32 because the TAP 30 monitors the network congestion state even during data transfer. A connection has already been established,
When the TAP 30 receives the information from the application, the TAP 30 adds a control header, adds a necessary header in the AAL 33, and is cellized.
It looks like this.

[Table 1] Table 1 for each control field in TAP format
This will be described with reference to FIG.

(TAI-time adjustment indicator) When this bit is set to "1", the TAP 30 determines that this cell is instructing time adjustment. If this bit is "0"
Then, it is a normal data transfer mode.

(CI-congestion indicator) If cells exceed a certain threshold value in the buffer while passing through the ATM exchanges 22,..., The ATM exchanges 22,.
EFCI of the PTI field of the header of the ATM cell 40
(Explicit Forward Congestion Indication) bit is set to “1” to notify the network that congestion is occurring in the ATM exchanges 22,. When the EFCI bit becomes “1”, the CI bit also becomes “1”,
Inform TAP 30 that congestion is occurring on this connection.

(DIR-direction) The TAP 30 is used in a loop configuration at the opposite end. It is used to determine the up / down.

(ACK-Authentication) When one terminal requests an operation, the other terminal certainly receives the information and is used to notify the terminal that the operation has been performed.

(OTC-timeout counter) The time adjustment is repeatedly performed between the opposed ends until the adjustment is successful. Each time the adjustment is performed, this counter is decremented. When the counter becomes zero, the adjustment in this connection is performed. Give up. That is, how many times the adjustment is repeated is determined.

(TAC-timing information) A value determined by calculating how much the time is shifted from the current sampling timing to send the application information is entered. This value is notified to the opposite end to notify that the time has shifted.

FIG. 4 shows a case in which the TAP adjusts the cell transmission timing to avoid cell contention and has no delay time fluctuation. In FIG. 4, terminals 1Aa, 1Ab, and 1Ac are:
The information Ia, I is switched by the ATM switch 22 via the input lines 6a, 6b, 6c to one output line 7.
b, Ic.

The terminals 1Aa, 1Ab, and 1Ac, in principle, adjust the transmission timing at times t1, t2, and t3, or at times t6, t7, and t8, as shown in FIG. Since the information Ia, Ib, Ic transferred to the input circuits 6a, 6b, 6c can insert the cells Ib, Ic coming from different source terminals 1B, 1C into the cell interval on the output line 7. Thus, a network can be designed without making useless free bandwidth.

The protocol TAP 30 is provided with the above-described functions, so that each terminal 1Aa, 1Ab, 1Ac
By adjusting the transmission timing of the channel and eliminating fluctuations in the delay time, the QoS conditions for the application are satisfied and the channel can be accommodated. TAP3
Numeral 0 is a function for adjusting timing when information is exchanged between terminals on the ATM network (network) 2. As described above, the TAP 30 is located between the application program 32 and the AAL 33,
It mediates between M and the application (see FIG. 2A). As the type of AAL (ATM Adaptation Layer: ATM adaptation layer) 33, the application information is assumed that the traffic type is CBR.
It is assumed that AAL1 recommended by ITU-T is used for BR traffic.

The operation of the terminal having the above-described various elements will be described below. First, the outline of the operation of the TAP 30 will be described. When the TAP 30 functions, the following 2
There are two cases.

First, at the time of connection setup, it is checked whether or not there is no contention between lines and a cell containing application information can be transmitted correctly. If contention has occurred, application information transmission timing To avoid conflicts.

Next, when congestion occurs in the network for some reason during data transfer, the data transfer is temporarily stopped, the CR information transmission timing is corrected, the contention is avoided, and then the data transfer is restarted. .

From another angle, TAP3
As described above, 0 plays a role mainly at the time of connection setup or monitoring whether or not congestion has occurred in the network.

To determine whether or not the congestion has occurred, there is a method in which the ABR service controls the traffic rate in the RM cell by looking at the EFCI field. However, this function is limited to ABR rate control and cannot be used in CBR service. TAP is
By monitoring the EFCI field, the CBR service performs congestion monitoring. Here, how the TAP adjusts the timing, and an operation example thereof will be described for the above two cases.

[Operation of Connection Setup] FIG.
Is a timing chart shown to explain the operation at the time of connection setup. Referring to FIG.
An operation of trying to establish a connection at the TAP level will be described, in which data transfer is not performed immediately after the connection is established in the ATM layer 34 and the TAP 30 is present. In FIG. 5, the terminals 1A and 1B
Are connected via the ATM network 2.

The cell sending function 36 of the source terminal 1A sets the TAI = 1 to send the ATM cell 40 to the destination terminal 1B in order to check the congestion state of the ATM network 2.

If congestion occurs in the ATM network 2 on this connection, the EFCI bit of the ATM cell 40 becomes "1" to notify the destination terminal 1B that congestion has occurred ( Timing 1 (TMG in the figure
Shown as 1. same as below)). Also, the terminal 1B simultaneously
The CI bit of the TM cell 40 is also set to “1”. Each bit is not shown in the ATM cell 40 shown in FIG. 3, but details of the bits are shown in Table 1.

In the destination terminal 1B, if the ATM cell 4
If the CI bit of 0 is “1”, if the ATM cell 40 is transmitted at this timing, congestion will be encountered.
The processing for operating the search function 37 to shift the timing is started. The search function 37 of the terminal 1B determines how much the timing is shifted, writes the value in the TAC field of the ATM cell 40, and sends it back to the source terminal 1A (timing 2). Note that the terminal 1B is simultaneously connected to the ATM
ACK = 1 and DIR = 1 of the cell 40 are set. The terminal 1B decrements the timeout counter by one.

In the source terminal 1A, the timing is adjusted again by the timing adjustment function 38, and the ATM cell 40 is sent to the destination terminal 1B (timing 3).

If the CI field of the received ATM cell 40 is "0" here, the destination terminal 1B knows that congestion has not occurred at this timing, and therefore the authentication (ACK) indicating that the connection has been established. = 1, CI =
0) to send to the source terminal 1A. At the same time, the terminal 1B
The TM cell 40 is sent to the terminal 1A with TAI = 1, DIR = 0 and TAC = 0.

However, if the terminal 1B
If it is determined that the CI field of the cell 40 is "1", the timing is shifted to the timing by operating the search function 37 since the network is congested even at this timing. The search function 37 of the terminal 1B determines how much the timing is shifted again, writes the value in the TAC field of the ATM cell 40, and
Send back to At this time, the timeout counter is also decremented by one.

If authentication is obtained from the destination terminal 1B (ACK = 1, CI = 0), the source terminal 1A considers that the connection has been established, enters the data transfer mode, and starts data transfer.

[Operation When Congestion Occurs During Data Transfer] FIG.
6 is a timing chart for explaining an operation when congestion occurs on the TM network 2 and application information cannot be transmitted in a normal form. Also in FIG.
A description will be given in a state where A and the terminal 1B are connected via the ATM network 2.

The originating terminal 1A stores the ATM cell 40 in the AT
It is assumed that the data is transferred to the destination terminal 1B via the M network 2 (timing 1). At this time, it is assumed that congestion occurs in the ATM network 2 and the EFCI of the ATM cell 40 changes to "1". The destination terminal 1B that has received the ATM cell 40 detects EFCI = "1" of the ATM cell 40 and knows that congestion has occurred in the ATM network 2 (timing 1).

The destination terminal 1B, having sensed the congestion, operates the cell sending function 36 to notify that the congestion has occurred on the source terminal 1A side in the field TAI of the ATM cell 40.
= "1", CI = "1", and notifies that the mode is changed from the data transfer mode to the timing adjustment mode, and operates the search function 37 to shift the timing. Is determined, and also notified to the transmission source terminal 1A (timing 2).

The source terminal 1A receives the congestion information from the destination terminal 1B via the ATM cell 40 and immediately operates the timing adjustment function 38 to change to the timing adjustment mode. In the source terminal 1A that has performed the timing adjustment, the TAI = "1" and the CI
= “0”, and sends the ATM cell 40 to the destination terminal 1B to check whether there is congestion on the ATM network 2 (timing 3).

If the destination terminal 1B receives the information (CI = “1”) that it is still congested at this timing, it operates the search function 37 again to determine the value of TAC, and The terminal 1A is notified that congestion is occurring and that the timing is to be shifted (timing 4).

The ATM cell 4 for this timing adjustment
The source terminal 1A that has received 0 changes the transmission timing of the ATM cell 40 by operating the timing adjustment function 38, and sets the TAI of the ATM cell 40 to "1",
CI = “0” is set, and the ATM cell 40 is sent to the destination terminal 1B in order to check again for congestion on the ATM network 2 (timing 5).

The destination terminal 1 B that has received the ATM cell 40
If the ATM cell 40 is examined and congestion does not occur (CI = "0"), it is authenticated that this timing is sufficient (Ack = "1", CI =
The ATM cell 40 in which "0" is set is transmitted to the source terminal 1A (timing 6).

The source terminal 1A, which has received the ATM cell 40, has been authenticated at this timing, so enters the data transfer mode and starts data transfer (timing 7).

As described above, the source terminal 1A and the destination terminal 1
The ATM cell 40 having the TAP unit 42 is transmitted to and received from B, so that the transmission timing can be adjusted.

Next, two methods, a random generation method and a table utilization method, are proposed as methods for determining the value of the time adjustment counter by the search function 37 of the terminal 1B.

[Random Generation Method] The search function 37 generates a uniform random number when generating the time adjustment counter, and distributes the random number uniformly within the cell interval length. This cell spacing is

## EQU1 ## The cell interval can be obtained by the following equation: random (). Therefore, the search function 37
Has a function capable of calculating the above equation (1).

FIG. 7 shows how cells move according to the value of the time adjustment counter determined by the random generation method.

If the CI of the ATM cell 40 is “1” and the ATM cell 40 is congested, the search function 37 calculates the cell interval using the above formula 1, and as a result, One of the cell slots within the cell interval is randomly selected, and this is set as the cell transmission timing. That is, when the cell 40a in the state of FIG. 7A is congested, a cell slot is randomly obtained by using the above equation 1, and the cell slot is changed to another cell slot as shown in FIG. 7B. The cell 40b is moved.

However, since the search function 37 sets the time adjustment counter quite randomly, the set value may again exceed the EFCI threshold value. This means that when the band is fully used, the number of available cell slots is reduced, and the probability of selecting the cell is reduced. Therefore, it takes time until all cells converge to a state where the EFCI threshold is not exceeded. There are cases.

However, since the protocol operation is only a calculation based on the random numbers, the implementation is light, and when a high-speed protocol operation is required, it is proposed as one of the implementation methods.

[Table Usage] In the search function 37, each time a cell arrives, the TAP 30 checks whether the CI field is "0" or "1", and sequentially writes the value in the table to generate a table.

[Table 2] Table 2 shows an example of a table of the TAP 30. In Table 2, the sequence number Cx is the number of the corresponding cell slot. The sequence numbers Cx are prepared for the slots in the cell interval. For example, in the case of 155 [Mbps], the slot number SN is

## EQU00002 ## SN = 1 / (sampling frequency.times.2.73.times.10.sup.- ⁶ ). In order, the process returns to the top and updates the value of CI.

In FIG. 8, when an empty slot is found with reference to the table of Table 2, the timing is adjusted so that the cell is moved to that location. That is, it is assumed that there is congestion, the search function 37 operates, and the cell transmission timing is changed with reference to Table 2. Then, the cell 40c having the sequence number C1 as shown in FIG. 8A is changed to the position of the sequence number C2 as the cell 40d as shown in FIG. 8B. As a result, if congestion disappears, cells are transmitted in this state at the cell transmission timing.

As described above, according to the embodiment of the present invention, there are the following advantages.

(1) The delay fluctuation of the ATM network 2 can be controlled to the order of 10 [microseconds].

(2) General-purpose equipment can be used in the ATM network, and there is no need to make special modifications to the ATM switch and the like in the ATM network.

(3) Since delay fluctuations can be suppressed, real-time application information can be reliably transferred.

In the above-described embodiment, two terminals 1A and 1B have been described. However, the same method for controlling delay fluctuation suppression in the asynchronous transfer mode network for all the terminals 1 connected to the ATM network 2 is described. It has a function to realize.

[Brief description of the drawings]

FIG. 1 is an ATM including an apparatus for implementing a delay fluctuation suppression control method in an asynchronous transfer mode network according to an embodiment of the present invention;
It is a block diagram showing a network.

FIG. 2A is a diagram showing a function provided in a CLAD for realizing a delay variation suppression control method in an asynchronous transfer mode network of the present invention. FIG. 2B is a block diagram showing a specific example of a function for realizing the delay variation suppression control method in the asynchronous transfer mode network of the present invention.

FIG. 3 is a diagram illustrating a structure of an ATM cell used in a delay variation suppression control method in an asynchronous transfer mode network according to the present invention;

FIG. 4 is an explanatory diagram showing a case where a TAP adjusts the timing of cell transmission, avoids cell contention, and has no delay time fluctuation.

FIG. 5 is a timing chart illustrating an operation during connection setup in the embodiment of the present invention.

FIG. 6 is a timing chart for explaining an operation when congestion occurs on the ATM network due to some trouble during data transfer and application information cannot be transmitted in a normal form in the embodiment of the present invention; It is a chart.

FIGS. 7A and 7B are explanatory diagrams showing a state in which a cell moves according to a value of a time adjustment counter determined by a random generation method in the embodiment of the present invention.

FIGS. 8 (a) and (b) illustrate how to adjust the timing so that if an empty slot is found with reference to the table of Table 2 in the embodiment of the present invention, the cell is moved to that location. FIG.

FIG. 9 is a block diagram showing some functions of the ATM switch.

FIG. 10 is a diagram for explaining a threshold value of an input buffer;
FIG. 3 is an explanatory diagram illustrating a configuration of a BR input buffer.

FIG. 11 is an explanatory diagram showing a situation that occurs when aiming at the same output port from different input paths.

[Explanation of symbols]

 1A, 1B terminal 2 ATM network 3A, 3B information transmission terminal 4A, 4B CLAD 6a, 6b, 6c input line 7 output line 21 ATM line 22 ATM switch 30 TAP 31 protocol stack 32 application program 33 AAL 34 ATM layer 35 physical layer 36 Cell transmission function 37 Search function 38 Timing adjustment function

Claims (4)

[Claims] When communication is performed between terminals connected to an asynchronous transfer mode network, a delay time between terminals that cannot be guaranteed by transmission quality control of the asynchronous transfer mode technology can be suppressed to an allowable value or less. Then, one terminal sends a cell for monitoring the state of the asynchronous transfer mode network to the other terminal by the cell sending function, and the other terminal receiving this cell sends congestion information to the cell by the search function. When there is, a search is made for a data transmission timing that is equal to or less than a desired specified value, and the timing of the search result is transmitted to one terminal. The one terminal has timing information in a cell received by the timing adjustment function. A delay fluctuation suppression control method in an asynchronous transfer mode network, wherein the transmission timing of the cell is adjusted and the transmission is performed again. 2. The search function includes a function of randomly searching for a timing at which the delay time becomes equal to or less than an allowable delay time, or a function of searching for a timing having a delay time as information and having a value equal to or less than a specified value. 2. The delay fluctuation suppression control method in an asynchronous transfer mode network according to claim 1, wherein 3. In a system for controlling communication between terminals connected to an asynchronous transfer mode network, a delay time between terminals, which cannot be guaranteed by transmission quality control of the asynchronous transfer mode technology, is reduced to an allowable value or less. The two terminals are capable of transmitting a cell for monitoring the state of the asynchronous transfer mode network, and a cell transmission function, when receiving the cell and when there is congestion information in the cell, search for a data transmission timing below the allowable value, A search function that sends the timing of the search results,
A delay fluctuation suppression control system in an asynchronous transfer mode network, comprising: a timing adjustment function of adjusting the transmission timing of a cell when the received cell has the timing information and retransmitting the cell. 4. The search function includes a function of randomly searching a timing at which the delay time becomes equal to or less than an allowable delay time, or a function of searching for a timing having a delay time as information and having a value equal to or less than a specified value. 4. A delay fluctuation suppression control system in an asynchronous transfer mode network according to claim 3, wherein: