JP3087941B2 - ATM communication network - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an asynchronous transfer mode (A
Used for TM (Asynchronous Transfer Mode) communication. The present invention relates to a communication network that controls a transmission rate between communication terminals to be close to a state satisfying fairness at a high speed when a plurality of communication terminals receiving a best effort (Best Effort) type service use the same route. Related to configuration and control method.

[0002]

2. Description of the Related Art In a conventional best-effort service in an ATM communication network, a cell for collecting information (RM cell: Resource Cell) is set up between an incoming and outgoing communication terminal in order to collect information on congestion and an acceptable bandwidth in the route. M
an aging cell), the network writes information in the RM cell, and the originating communication terminal refers to it to control the cell transmission rate.

[0003] For example, ABR (Available Bit) which is a typical best effort type service in an ATM communication network.
In the service based on the (Rate) protocol (see ATM Forum (atmf95-0013R2)), first, all the nodes between the outgoing and incoming communication terminals including the communication terminal are configured to operate based on the ABR protocol.

This conventional example will be described with reference to FIGS. FIG. 20 is an overall configuration diagram of a conventional ATM communication network. FIG. 21 is a diagram showing the configuration of the RM cell. FIG. 22 is a flowchart showing the operation of the communication terminal on the calling side. FIG. 23 is a flowchart showing the operation of the destination local exchange and transit exchange. FIG. 24 is a flowchart showing the operation of the communication terminal on the receiving side. A shown in FIG.
The TM communication network is configured based on the ABR protocol. In FIG. 20, reference numerals 20 and 40 are local exchanges,
Represents a relay exchange, 5 represents a transmission line, 13-1 represents a communication terminal on the calling side, and 13-2 represents a communication terminal on the receiving side.

[0005] Between the originating and terminating communication terminals, the RM cell is periodically transmitted from the originating communication terminal 13-1 for each originating and terminating pair, and the transit exchange 30 writes congestion information and the amount of acceptable bandwidth on the route, and The communication terminal 13-2 on the side loops it back and notifies the communication terminal 13-1 on the calling side of the presence or absence of congestion on the route.

The communication terminal 13-1 on the calling side must transmit at a cell transmission rate called an ACR (Allowed Cell Rate) which is lower than the allowable cell transmission rate according to the rules of the ABR protocol.

When the communication terminal 13-1 on the originating side receives the notification of the congestion by the RM cell, it reduces the ACR based on the ABR protocol. Conversely, when it is notified that there is no congestion, the ACR is raised based on the ABR protocol.

[0008] If the communication terminal 13-1 on the calling side has a minimum value of the acceptable bandwidth of the network notified by the RM cell, the communication terminal 13-1 of the value and the newly calculated ACR value,
The transmission rate is changed to a cell rate equal to or smaller than the smaller value. If not, the transmission rate is changed to a cell transmission rate equal to or lower than the ACR.

When a new VC (virtual channel) starts data transmission, after transmitting the first RM cell, the transmission rate of a specified cell at the start of transmission called an ICR (Initial Cell Rate) It is allowed to send:

[0010] After the first RM cell returns, the cell transmission rate is controlled by the procedure described above. The operation of the originating communication terminal 13-1 based on the ABR protocol in the ATM communication network of FIG. 20 is shown in FIG.
0, the operation of the transit exchange 30 is shown in FIG. 23, and the operation of the destination communication terminal 13-2 is shown in FIG. As shown in FIG. 22A, the communication terminal 13-1 on the calling side generates an RM cell (S1), initializes it (S2), and sends it out (S2).
3). The RM cell includes the originating local exchange 20, the transit exchange 30, the destination local exchange 40, and the destination communication terminal 13-.
Then, as shown in FIG. 22B, the call is returned to the communication terminal 13-1 on the calling side (S11). If there is a congestion notification in the RM cell (S12), the ACR is reduced (S14); otherwise, the ACR is increased (S13).
Thereby, the transmission rate of the cell is changed (S15).

Originating local exchange 20 and transit exchange 3
0, at the destination local exchange 40, the originating communication terminal 13
When the RM cell transmitted from -1 is received (S21),
The allowable cell transmission rate is written into the ER field (S22), and when it is determined that the cell is in a congested state (S23), the CI
The congestion notification is written in the field (S24), and the RM cell is transmitted (S25).

When the communication terminal 13-2 on the receiving side receives the RM cell sent from the communication terminal 13-1 on the calling side, it receives the RM cell (S
21) Write an allowable cell transmission rate in the ER field (S22), and determine that the cell is in a congested state (S2).
3) Write a congestion notification in the CI field (S24)
The RM cell is turned back (S26).

[0013] In the conventional ABR, when congestion occurs due to a start of transmission of a new communication terminal or an increase in the transmission rate of a cell and the notification is made, each of the notified communication terminals lowers the transmission rate and consequently the available capacity is reduced. Each communication terminal increases the transmission rate again when notified that the communication terminal is out of the congestion state. By repeating this, the transmission rate gradually approaches a fair transmission rate.

[0014]

However, when the distance between communication terminals is large, it takes time to transmit the RM cell,
It takes time to control the ACR of a communication terminal that newly transmits or a communication terminal that has already transmitted. Therefore,
It takes time to converge to a fair amount of bandwidth distribution. Also, it is difficult to sufficiently follow the ever-changing transmission rate and network conditions.

[0015] To shorten the time required for raising the ACR, it can be avoided by setting the ICR of each communication terminal to be high. However, when the distance between the communication terminals is large, the time until notification of congestion is large. Take it. It is necessary to take measures such as increasing the buffer length in the network or reducing the usage rate of the network.

Further, even when the distance between the communication terminals is short,
It takes a certain amount of time to converge to a transmission rate that satisfies fairness, and there is a potential demand to reduce this.

The present invention has been made in view of such a background, and an object of the present invention is to provide an ATM communication network capable of fairly controlling a transmission rate between a plurality of communication terminals in a best-effort service. Aim. SUMMARY OF THE INVENTION It is an object of the present invention to provide an ATM communication network capable of quickly converging a transmission rate between a plurality of communication terminals to a fair state at a high speed. An object of the present invention is to provide an ATM communication network capable of fairly controlling the cell transmission rate of each communication terminal without making transmission delay a problem even when the distance between a plurality of communication terminals is large. With the goal.

[0018]

SUMMARY OF THE INVENTION According to the present invention, a subscriber exchange accommodating a plurality of communication terminals receiving a best-effort service is provided with a transmission rate satisfying fairness among the communication terminals in controlling the transmission rate of the communication terminals. And a control method for causing convergence at a high speed.

In the prior art, an information collection cell is made to reciprocate between the originating and terminating communication terminals, the ATM communication network writes congestion information and information on an acceptable bandwidth amount, and the destination communication terminal loops back the cell. On the other hand, the originating communication terminal controls the transmission rate only by referring to the information on the cell. The configuration of the communication network, the setting of the transmission rate control timing, the logic of the transmission rate control, and the speed of convergence of the transmission rate are different from those of the conventional technology.

That is, the present invention is an ATM communication network comprising a communication terminal, a subscriber exchange accommodating the communication terminal, and means for setting a virtual path between the plurality of subscriber exchanges.

Here, a feature of the present invention is that an exchange through which a virtual path passes or terminates a virtual path transmits route information including free band information of a virtual path related to the exchange to the network. Means, wherein the local exchange includes means for collecting the route information, and means for calculating and setting a cell transmission rate allowed for the communication terminal according to the collected route information.

The local exchange collects route information irrespective of whether or not the communication terminal accommodated in the local exchange performs transmission. For this reason, it is possible to quickly calculate the transmission rate of the cell together with the transmission start request from the communication terminal and return whether or not transmission can be started to the communication terminal.

The free band information is numerical information, and the means for calculating and setting the free band information includes a constant C (0 <C ≦
Means for calculating the permissible cell transmission rate by multiplying by 1). The value of the constant C can be set appropriately in consideration of the characteristics of the ATM communication network, the type of information, and other factors.

When the minimum transmission rate of the cell included in the transmission start request from the communication terminal is smaller than the allowable transmission rate of the cell, the initial transmission rate of the cell of the communication terminal is changed to the transmission of the allowable cell. It is desirable to have control means for setting the rate.

In the present invention, RM cells are not transmitted / received between the local exchanges, and the transmission start request is sent from the communication terminal to determine whether or not the transmission start request is possible, and until the transmission rate of the cell is set. Since the time is characterized by a short time, when the minimum transmission rate of the cell included in the transmission start request is smaller than the allowable transmission rate of the cell, the transmission rate of the cell is quickly increased and the transmission of the communication terminal is performed. Corresponding.

The permissible increase and decrease of the cell transmission rate can be executed stepwise for each unit increase. The amount of increase in the transmission rate of the communication terminal that can be increased at one time is determined in advance, and this is defined as a unit increase. When the allowable cell transmission rate is equal to or less than the unit increase, the transmission rate is increased by the unit increase.
After the increase, the same procedure is performed. If the allowable cell transmission rate is still equal to or greater than the unit increase,
The transmission rate is increased again by the unit increment. By repeating this procedure, the transmission rate of the communication terminal can be increased at a high speed. Rather than gradually increasing the transmission rate while observing the situation of the entire route, the unit increment is set in advance, and the unit increment is increased at once by the judgment of only the local exchange. The transmission rate can be increased stepwise at high speed.

The route information is a quantity indicating the amount of free bandwidth of a virtual path included in the route in a stepwise manner, and the means for calculating and setting uniquely sets an allowable cell transmission rate according to this quantity. Means for performing the operation may be included. For example, a plurality of thresholds are provided for the available bandwidth, and the transmission rate is calculated by comparing with the thresholds. Furthermore, a threshold is also provided for the transmission rate of the communication terminal, and is considered in consideration of the result derived from the available bandwidth,
It is also possible to select a communication terminal to be notified of congestion.

Alternatively, the route information is a quantity indicating a queue length of a cell buffer provided in a node included in the route in a stepwise manner. Means for setting the rate uniquely may be included. For example, a plurality of thresholds are provided for the queue length of the cell buffer, and the transmission rate is calculated by comparing with the thresholds. Furthermore, a threshold value may be provided for the transmission rate of the communication terminal, and a communication terminal to be notified of congestion may be selected in consideration of the result derived from the queue length of the cell buffer.

When an exchange for transmitting an RM cell for transmitting the route information to another exchange is mixed in the ATM communication network of the present invention, the means for calculating and setting includes means for discarding the received RM cell. It is desirable to include.

For example, when the local exchange calculates the cell transmission rate and writes the operation result in the RM cell to notify the communication terminal, if another RM cell arrives from another, the local exchange will Should be identified and discarded. This can prevent the communication terminal from malfunctioning due to a plurality of different information.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. FIG. 1 is an overall configuration diagram of an ATM communication network according to an embodiment of the present invention. 1-1 and 1-2 are communication terminals on the calling side, and 2
Is an originating subscriber exchange, 3 is a relay exchange, 4 is a destination subscriber exchange, 5 is a transmission line, and 6-1 and 6-2 are destination communication terminals. FIG. 2 is a block diagram of a main part of the local exchange on the calling side. Reference numeral 10 denotes a route information collection unit, and reference numeral 12 denotes a transmission rate calculation control unit. FIG. 3 is a block diagram of the main parts of the transit exchange and the destination local exchange. Reference numeral 14 denotes a route information sending unit.

According to the present invention, the communication terminals 1-1 and 1-2 on the calling side are provided.
Means for setting a virtual path between the originating local exchange 2 accommodating the communication terminals 1-1 and 1-2, and the originating local exchange 2 and the destination local exchange 4. An ATM communication network comprising: The means for setting the virtual path includes the originating local exchange 2, the destination local exchange 4, the transit exchange 3, and the originating communication terminals 1-1 and 1-.
2. It is provided in each of the communication terminals 6-1 and 6-2 on the receiving side, but is not shown because it is not a main part of the present invention.

Here, the feature of the present invention is that the transit exchange 3 which is an exchange through which the virtual path passes or terminates the virtual path, and the subscriber exchange 4 on the receiving side are free of the virtual path related to the exchange. It includes a route information transmitting unit 14 as means for transmitting route information including band information into the network, and the originating local exchange 2
A route information collecting unit 10 as a means for collecting the route information, and a means for calculating and setting a cell transmission rate allowed for the communication terminals 1-1 and 1-2 on the calling side according to the collected route information. Transmission rate calculation control unit 12
And where it is.

The relay exchange 3 and the destination subscriber exchange 4 are:
A route information transmitting unit 14 for transmitting route information including free bandwidth information of a virtual path to the originating local exchange 2;
Send to. As the transmission timing, the transmission may be performed at a predetermined cycle or may be performed at a timing when the situation changes.

[0035]

【Example】

(First Embodiment) The communication terminals 1-1 and 1-2 on the calling side are ABR
Communicate based on protocol. The originating local exchange 2 emulates the ABR protocol with the originating communication terminals 1-1 and 1-2 so as to be connectable.
The transit exchange 3, the subscriber exchange 4 on the receiving side, and the communication terminals 6-1 and 6-2 on the receiving side do not necessarily need to operate based on the ABR protocol. However, the transit exchange 3 and the destination local exchange 4 have to notify the originating local exchange 2 of the use status of the route as route information when there is a periodic or state change. The current available bandwidth is calculated based on information on the use status notified to the originating local exchange 2 and / or the transmission status from each of the communication terminals 1-1 and 1-2, or both.

The operation of the originating local exchange 2 when there is a request from the communication terminal 1-1 or 1-2 to newly start transmission via the route will be described with reference to the flowchart of FIG. FIG. 4 is a flowchart showing the operation of the originating local exchange 2. When a transmission start request is received from a new communication terminal (S30), a constant C
Initial transmission rate IC for transmission of a value multiplied by (0 <C ≦ 1)
R (S31). The constant C is a parameter determined to prevent the information at the time of acceptance from being shifted from the current state and setting an incorrect transmission rate. If the ICR is smaller than the minimum transmission rate MCR (Minimum Cell Rate) required from the communication terminals 1-1 and 1-2 on the calling side (S32), it is dangerous to accept it as it is. It is necessary to perform negotiation (negotiation) again with the terminals 1-1 and 1-2, and in this state, it is not accepted (S33). If IC
If R is equal to or greater than MCR (S32), transmission by ICR is permitted (S34). According to the first embodiment of the present invention, it is instantaneously determined whether a transmission start request from a new communication terminal 1-1 or 1-2 on the calling side is accepted or not, and the accepted communication terminal 1-1 or 1 on the calling side is accepted. -2 from the ICR.

(Second Embodiment) FIG. 5 is a block diagram showing a main part of an ATM communication network according to a second embodiment of the present invention. 1-1, 1-2 and 1-3 perform communication according to the ABR protocol. The originating communication terminal, 2 is an originating local exchange for emulating the ABR protocol for each communication terminal, and 5 is a part of a route shared by the originating communication terminals 1-1 to 1-3. FIG. 6 is a diagram showing a band use state before the control of the second embodiment of the present invention is applied in the ATM communication network configuration of FIG. In FIG. 6, Wtotal
Is the total bandwidth of the route, Wa is the free bandwidth of the route, W1 is the bandwidth used by the communication terminal 1-1 on the calling side, W2 is the bandwidth used by the communication terminal 1-2 on the calling side, and W3 is the bandwidth used. Represents the used bandwidth amount of the communication terminal 1-3 on the side. In FIG. 6, after transmitting the first RM cell at time t0, the communication terminal 1-3 on the calling side immediately starts transmitting data at the initial transmission rate ICR indicated by W3.

FIG. 7 is a diagram showing the operation of the second embodiment of the present invention and the change in the used bandwidth amount due to the operation. Available bandwidth Wa
Is multiplied by a constant C (0 <C ≦ 1) is the communication terminal 1-3 on the calling side that started transmission at the transmission rate ICR at t0.
When the transmission rate is larger than the unit increase in the unit time within the unit time, an RM cell notifying that congestion does not occur in the originating local exchange 2 is generated, and the originating communication terminal 1 is generated.
-3, allowing the transmission rate to increase. In FIG. 7, the communication terminal 1-3 on the calling side receives the RM cell at time t1, and increases the transmission rate. Thereafter, when the value obtained by multiplying the available bandwidth amount Wa by the constant C is still larger, the originating local exchange 2 further generates and transmits an RM cell.
FIG. 8 is a flowchart showing the operation of the local exchange 2 in the second embodiment of the present invention. When a free band occurs (S40), a value obtained by multiplying the free band amount by a constant C is calculated (S41). When the value obtained by multiplying the available bandwidth by the constant C is larger than the unit increase of the transmission rate (S42), the originating local exchange 2 notifies the originating communication terminals 1-1 to 1-3 of no congestion. (S43), and the communication terminals 1-1 to 1-1 on the calling side are executed.
-3 increases the transmission rate by the unit increment. According to the second embodiment of the present invention, rather than gradually increasing the transmission rate while observing the status of the entire route, the unit increment is set in advance, and only the originating local exchange 2 makes a judgment. Since the unit increment is increased at a stretch, the transmission rates of the communication terminals 1-1 to 1-3 on the calling side can be increased stepwise at high speed.

(Third Embodiment) FIGS. 9 to 14 are views for explaining a third embodiment of the present invention. FIG. 9 is a configuration diagram of a main part of an ATM communication network according to a third embodiment of the present invention. In FIG. 9, the communication terminals 1-1 to 1-4 on the calling side are shown.
Is a communication terminal on the calling side that performs communication according to the ABR protocol, 2 is a subscriber exchange that emulates the ABR protocol for each communication terminal, and 5 is a part of a route shared by each communication terminal. FIG. 10 is a diagram showing the used bandwidth of each communication terminal at a certain point in time, where Wa is the free bandwidth in the route, and W1, W2, W3, and W4 are the communication terminals 1-1 to 1-4 on the calling side, respectively. Represents the used bandwidth. In FIG. 10, the amount of used bandwidth varies greatly, and there is a possibility that unfairness of the transmission rate occurs between communication terminals. FIG. 11 shows the maximum cell transmission rate (PCR) and the minimum cell transmission rate (MCR) of the transmission rates from the originating communication terminals 1-1 to 1-4 in the same situation as in FIG. Threshold value Rth
It is a figure showing the relationship between 1 and Rth2. FIG. 12 shows the amount of free bandwidth and the thresholds Wth1 and Wth in the third embodiment of the present invention.
It is a figure showing the relationship of th2 and Wth3.

A control algorithm according to the third embodiment of the present invention will be described with reference to FIGS. FIG. 13 is a flowchart of an algorithm for notifying congestion to each communication terminal by the local exchange. FIG. 14 is a diagram illustrating the relationship between the amount of available bandwidth, the transmission rate of the communication terminal, and the content of notification of congestion at that time. The originating local exchange 2 monitors the amount of available bandwidth, and compares the value with the thresholds Wth1 and Wt.
h2 and Wth3 are compared. The free bandwidth amount Wa is equal to the threshold W
When it is smaller than th1 (S51), it notifies the congestion to all the communication terminals 1-1 to 1-4 on the calling side (S52). When the available bandwidth Wa is equal to or larger than the threshold Wth1 and smaller than the threshold Wth2 (S53), the communication terminal having the transmission rate equal to or larger than the threshold Rth1 is notified of the congestion (S54). When the available bandwidth Wa is equal to or greater than the threshold value Wth2 and smaller than the threshold value Wth3 (S55), the communication terminal having the transmission rate equal to or less than Rth2 is notified of no congestion (S56). If the available bandwidth Wa is equal to or larger than the threshold value Wth3 (S57), all the communication terminals 1-1 to 1-4 on the calling side are notified of no congestion (S5).
8). Then, as shown in FIG. 14, based on the comparison result, the congestion information is transmitted to each of the communication terminals 1-1 to 1-4 on the calling side by generating and transmitting an RM cell. Each of the communication terminals 1-1 to 1-4 on the calling side has an opportunity to increase the transmission rate when receiving notification of no congestion according to the ABR protocol. Conversely, when the notification that there is congestion is received, the transmission rate is reduced.

In the third embodiment of the present invention, the communication terminals 1-1 to 1-4 on the calling side according to the transmission rate and the available bandwidth before the change.
Are different in the timing of notifying congestion. As a result, when there is room in the bandwidth, the effect of shifting the entire transmission rate to a high transmission rate, the effect of reducing the variation in the transmission rate and imparting fairness among communication terminals, particularly, the transmission rate of a low transmission rate Has the effect of increasing the speed at high speed.
Conversely, when the band starts to run short, the transmission rate is reduced for high rates, and when the band runs short, the overall transmission rate is lowered. In each case, R
This function can be realized without the M cell having to go back and forth between the originating and terminating communication terminals.

(Fourth Embodiment) FIG. 15 is an overall configuration diagram of an ATM communication network according to a fourth embodiment of the present invention. 1-1 to 1-4 are communication terminals on the originating side, 2 is the local exchange on the originating side, 3 is the relay exchange, 4 is the local exchange on the receiving side, 5 is a transmission line, and 6-1 to 6-2.
6-4 is a communication terminal on the receiving side. The configuration of the fourth embodiment of the present invention will be described with reference to FIG.

The communication terminals 1-1 to 1-4 on the calling side perform communication based on the ABR protocol. Originating local exchange 2
Emulates the ABR protocol to the communication terminals 1-1 to 1-4 on the calling side to enable connection.
The transit exchange 3, the destination subscriber exchange 4, and the destination communication terminals 6-1 to 6-4 do not necessarily need to operate based on the ABR protocol. The transit exchange 3 and the destination local exchange 4 notify the number of cells stored in the respective queue buffers when the originating local exchange 2 changes periodically or when the situation changes. Originating local exchange 2
Determines the current usage status based on the notified queue buffer length and the number of cells stored in the queue buffer of the originating local exchange 2.

FIG. 16 shows the maximum cell transmission rate (PCR).
FIG. 13 is a diagram illustrating the relationship between the minimum cell transmission rate (MCR), threshold values Rth1 and Rth2 in the fourth embodiment of the present invention, and the transmission rate of each communication terminal. In FIG. 16, Rate1 to Rate4 are communication terminals 1-1 to 1-4 on the calling side, respectively.
Is the transmission rate. In FIG. 16, the transmission rates vary greatly, and there is a possibility that the transmission rates among the communication terminals 1-1 to 1-4 on the calling side are unfair. FIG.
7 is the free bandwidth and the threshold Qt in the fourth embodiment of the present invention.
It is a figure showing the relationship of h1, Qth2, and Qth3.

FIG. 18 is a flowchart of an algorithm for controlling the transmission rate of each of the communication terminals 1-1 to 1-4 on the calling side by the local exchange 2 on the calling side. In FIG. 18, Qu is the maximum value among the buffer usages notified to the local exchange 2 on the calling side. Originating local exchange 2
Compares Qu with threshold values Qth1, Qth2, and Qth3. When the maximum value Qu of the buffer usage is equal to or larger than the threshold value Qth3 (S61), all of the communication terminals 1-1 to 1-1 on the calling side.
4 is notified of congestion (S62). When the maximum value Qu of the buffer usage is equal to or greater than the threshold value Qth2 and smaller than the threshold value Qth3 (S63), the transmission rate is notified to the communication terminals 1-1 to 1-4 on the calling side whose transmission rate is equal to or greater than the threshold value Rth1 (S6).
4). When the maximum value Qu of the buffer usage is equal to or larger than the threshold Qth1 and smaller than the threshold Qth2 (S65), the communication terminals 1-1 to 1-1 on the outgoing side whose transmission rate is equal to or smaller than the threshold Rth2.
-4 is notified of no congestion (S66). When the maximum value Qu of the buffer usage is smaller than the threshold value Qth1 (S6
7), all the communication terminals 1-1 to 1-4 on the calling side are notified of no congestion (S68). 19 is a diagram showing the relationship between the maximum value Qu of the buffer usage, the transmission rates of the communication terminals 1-1 to 1-4 on the calling side, and the notification contents of congestion at that time. As shown in FIG. Generates RM cells for congestion information in the communication terminals 1-1 to 1-4 on the calling side based on
Tell by sending. Communication terminal 1-1 of each calling side
4 has an opportunity to increase the transmission rate when it is notified that there is no congestion according to the ABR protocol. Conversely, when it is notified that there is congestion, it lowers the transmission rate.

In the fourth embodiment of the present invention, the timing of notifying congestion to the communication terminals 1-1 to 1-4 on the calling side differs according to the transmission rate before the change and the buffer length used in common. . Accordingly, when there is room in the bandwidth or the buffer, the effect of shifting the whole to a high transmission rate, the variation of the transmission rate is reduced, and the communication terminals 1-1 to 1-1 on the calling side are reduced.
There is an effect of imparting fairness among the information 1-4, and in particular, an effect of rapidly increasing the transmission rate of a low transmission rate. Conversely, when the bandwidth or the buffer length starts to run short, the transmission rate is reduced although the transmission rate is high, and when the band and buffer length are further short, the overall transmission rate is lowered. In any case, this function can be realized without the RM cell having to go back and forth between the communication terminals that send and receive.

(Fifth Embodiment) In the ATM communication network of the present invention, if a part of the ATM communication network includes another system, for example, the system described in the conventional example, the transit exchange 3 and the receiving side The local exchange 4 and the destination communication terminals 6-1 to 6-
4 may voluntarily transmit RM cells. In such a case, if it is described in the RM cell that there is no congestion, in the local exchange 2, the communication terminals 1-1 to 1-1 on the calling side are called.
Even if the operation of lowering the transmission rate of -4 is performed, the opposite operation is required by the returned RM cell. Therefore, in the fifth embodiment of the present invention, the communication terminals 1-1 to 1-4 on the calling side serving as conditions for notifying congestion are set.
Of the originating subscriber exchange 2
Discard at According to the fourth embodiment of the present invention, there is an effect of preventing transmission rate control by RM cells having erroneous congestion information.

[0048]

As described above, according to the present invention,
It is possible to fairly control the transmission rate between a plurality of communication terminals in the best-effort service. Furthermore, it is possible to quickly converge the transmission rates among a plurality of communication terminals to a fair state. As a result, even when the distance between a plurality of communication terminals is large, it is possible to control the cell transmission rate of each communication terminal fairly without making transmission delay a problem.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an ATM communication network according to an embodiment of the present invention.

FIG. 2 is a block diagram of a main part of an originating local exchange.

FIG. 3 is a block diagram showing the main parts of a transit exchange and a destination local exchange.

FIG. 4 is a flowchart showing the operation of the originating local exchange;

FIG. 5 is a configuration diagram of a main part of an ATM communication network according to a second embodiment of the present invention.

FIG. 6 is a diagram illustrating a band use state before control according to the second embodiment of the present invention is performed.

FIG. 7 is a diagram showing an operation of the second embodiment of the present invention and a change in the used bandwidth amount due to the operation.

FIG. 8 is a flowchart showing the operation of the originating local exchange in the second embodiment of the present invention.

FIG. 9 is a configuration diagram of a main part of an ATM communication network according to a third embodiment of the present invention.

FIG. 10 is a diagram illustrating a used bandwidth amount of each communication terminal at a certain time.

FIG. 11 is a diagram illustrating a relationship between a maximum cell transmission rate (PCR) and a minimum cell transmission rate (MCR) of transmission rates from a communication terminal and threshold values Rth1 and Rth2 in the third embodiment of the present invention.

FIG. 12 is a diagram showing the relationship between the amount of free bandwidth and threshold values Wth1, Wth2, and Wth3 in the third embodiment of the present invention.

FIG. 13 is a flowchart of an algorithm for notifying congestion to each communication terminal by the local exchange;

FIG. 14 is a diagram illustrating a relationship between an available bandwidth, a transmission rate of a communication terminal, and a notification content of congestion at that time.

FIG. 15 is an overall configuration diagram of an ATM communication network according to a fourth embodiment of the present invention.

FIG. 16 is a diagram illustrating a relationship between a maximum cell transmission rate (PCR) and a minimum cell transmission rate (MCR), and threshold values Rth1 and Rth2 and a transmission rate of each communication terminal in the fourth embodiment of the present invention.

FIG. 17 is a diagram showing the relationship between the amount of available bandwidth and threshold values Qth1, Qth2, and Qth3 in the fourth embodiment of the present invention.

FIG. 18 is a flowchart of an algorithm for controlling the transmission rate of each communication terminal by the local exchange.

FIG. 19 is a diagram showing the relationship between the maximum value Qu of the buffer usage, the transmission rate of the communication terminal, and the content of notification of congestion at that time.

FIG. 20 is an overall configuration diagram of a conventional ATM communication network.

FIG. 21 is a diagram showing a configuration of an RM cell.

FIG. 22 is a flowchart showing the operation of the communication terminal on the calling side;

FIG. 23 is a flowchart showing the operation of the destination local exchange and transit exchange.

FIG. 24 is a flowchart showing the operation of the communication terminal on the receiving side.

[Explanation of symbols]

1-1 to 1-4, 3-1, 3-2, 6-1 to 6-4, 1
3-1, 13-2 Communication terminal 2, 4, 20, 40 Subscriber exchange 3, 30 Transit exchange 5 Transmission line 10 Route information collection unit 12 Transmission rate operation control unit 14 Route information transmission unit

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-7-231322 (JP, A) 1995 IEICE Communication Society Conference B-347 (August 15, 1995) IEICE 1995 Communications Society Conference B-345 (August 15, 1995) IEICE Technical Report SS E95-30 (July 14, 1995) IEICE Technical Research Report SS E95-14 (May 1995) (19th) (58) Fields surveyed (Int. Cl. ⁷ , DB name) H04L 12/28 H04L 12/56

Claims (2)

(57) [Claims] An ATM communication network comprising a communication terminal, a plurality of local exchanges accommodating the communication terminal, and means for setting a virtual path between the plurality of local exchanges, wherein the virtual path is An exchange that passes through or terminates the virtual path, includes means for transmitting route information including free bandwidth information of the virtual path relating to the exchange into the network, wherein the subscriber exchange collects the route information; Means for calculating and setting the cell transmission rate allowed for the communication terminal according to the collected route information ;
Minimum number of cells included in the transmission start request from the communication terminal
Transmission rate (MCR) and cells allowed for the communication terminal
Comparison with the initial transmission rate (ICR)
And the minimum transmission rate is the initial transmission rate.
If larger, notify the communication terminal that it is not acceptable
And the minimum transmission rate is smaller than the initial transmission rate.
In this case, the communication terminal is provided with the initial transmission rate.
Means for permitting transmission . 2. The free bandwidth information is numerical information, and the calculation setting means includes a constant C (0 <C) in the free bandwidth information.
2. The ATM communication network according to claim 1, further comprising means for calculating the permissible cell transmission rate by multiplying by ≤1).