JPH09247174A - Atm communication network - Google Patents

Abstract

PROBLEM TO BE SOLVED: To mix a speed explicit system and a congestion notice control system in a single network by allowing a subscriber and relay exchange to have each of cell temporary storage buffer, detection an notice and providing a specific means to each of transmission or reception terminal equipment. SOLUTION: A virtual transmission terminal equipment 5 is provided between a transmitter side subscriber network 1 and a relay network 2, and a virtual reception terminal equipment 7 is provided between the relay network 2 and a recipient subscriber network 3. The virtual transmission terminal equipment 5 and the virtual reception terminal equipment 7 are subscriber exchanges. A data cell 9 is transferred to a reception terminal equipment 8 via the virtual transmission terminal equipment 5, a relay exchange 6 and the virtual reception terminal equipment 7 from the transmission terminal equipment 4 through a virtual channel. The reception terminal equipment 8 transfers an RM cell 12 describing a receptible cell transfer speed to the virtual reception terminal equipment T for a prescribed period. The virtual reception terminal equipment 7 reads the value described in the RM cell 12 and the data cell 9 is sent to the reception terminal equipment 8 at a speed less than the value.

Description

Detailed Description of the Invention

[0001]

The present invention relates to an ATM (Asynchronou).
s Transfer Mode: Used for communication.
The present invention relates to a technique for mixing two different congestion control methods in one network.

[0002]

2. Description of the Related Art ATM communication is a communication system for transferring a fixed-length packet consisting of a 5-byte header called a cell and a 48-byte payload. In the ATM communication network, a virtual transmission line called a virtual channel corresponds to each line. In the ATM communication network, by preparing a plurality of service classes, it is possible to transfer information having different traffic characteristics such as voice, video and data or different required quality at high speed in the same network.

As a service class for suppressing cell loss by changing the transfer rate according to the cell flow rate in the network, ABR (A
vailable Bit Rate) service has been devised (reference: The ATM Forum "UNI ver.3.1").

This conventional example will be described with reference to FIG. FIG. 6 is a speed explicit method which is one of the ABR service methods (reference: SSSathaye, "ATM Forum Traffic Manageme
nt Specification Version 4.0 ", ATM-Forum / 95-0013R
It is a figure which shows 8.).

In the speed explicit method, an RM (Resource Management) cell 87 is periodically transmitted and received between the transmitting terminal 4 and the receiving terminal 8 for each virtual channel and used for a speed notification signal. The subscriber exchange 82, the transit exchange 83, and the subscriber exchange 84 can extract the RM cell 87, read the speed information described in the RM cell 87, observe the traffic volume of the own exchange, and receive the cell. Calculate the speed,
The calculated speed is compared with the speed read from the RM cell, a smaller speed is written in the RM cell, and the RM cell is sent again. Further, the subscriber exchange 82, the transit exchange 83, and the subscriber exchange 84 can write and send the speed information to the folded RM cell.

The receiving terminal 8 extracts the RM cell 87, reads the described speed information, calculates the speed at which the cell can be received, and compares the calculated speed with the read speed.
Write a smaller speed to the RM cell and fold the RM cell back.

The transmitting terminal 4 reads the speed information described in the RM cell, and transmits the cell at a speed equal to or lower than the speed to transfer information without cell loss.

That is, in the speed explicit method, the cell flow speed is directly changed according to the minimum traffic amount that can be transferred, so that efficient information transfer can be performed.

[0009]

In theory, the speed explicit method is an excellent method for efficient information transfer. However, as shown in FIG. 6, means (A) for extracting the RM cell and reading the speed, means (B) for writing and inserting the speed in the RM cell, means (C) for observing the traffic volume, and traffic Since it cannot be realized unless all the exchanges on the route have the means (D) for calculating the receivable speed from the amount, the total equipment cost between the transmitting terminal and the receiving terminal becomes extremely large. In particular, a large-scale transit switch performs cell processing for a large number of virtual channels as compared with a subscriber switch, so that the speed explicit method is difficult.

Therefore, in an actual ATM communication network, the queue length of a buffer that temporarily stores cells is measured, and if the queue length of the buffer of the own node exceeds a threshold value, a congestion notification is sent to another node, and this congestion notification is sent. Generally, the node that has received the cell flow control (hereinafter, this method is referred to as a congestion notification control method) by a simple congestion notification such as stopping cell transmission.

Therefore, it is unrealistic to configure the speed explicit method in the entire ATM communication network, and there are two methods in which the speed explicit method is performed in a part and the congestion notification control method is used in another part. It is more realistic to construct an ATM communication network.

However, in the conventional technique, there is no means for providing an interface between these two systems, and it has been impossible to construct an ATM communication network in which the two systems coexist.

The present invention has been made in view of such a background, and an object thereof is to provide an ATM communication network in which a speed explicit method and a congestion notification control method can coexist in one network. To do. An object of the present invention is to provide an ATM communication network capable of efficiently transferring information while maintaining a simple structure. It is an object of the present invention to provide a subscriber exchange that can handle both the speed explicit method and the congestion notification control method in common.

[0014]

SUMMARY OF THE INVENTION A first aspect of the present invention is that A
A TM communication network, which includes means for transmitting an RM cell and transmitting the cell in accordance with the cell transfer rate information written in the RM cell received back, and R
This R is received according to its own free band information after receiving M cells.
A receiving terminal having means for writing cell transfer rate information in the M cell and sending back the RM cell, and a relay network interposed between the receiving terminal and the transmitting terminal. Is an ATM communication network including two subscriber exchanges in which the transmitting terminal and the receiving terminal are respectively accommodated, and a relay exchange.

Here, a feature of the present invention is that the subscriber exchange and the transit exchange are provided with a buffer for temporarily storing cells, and means for detecting the presence or absence of congestion according to the queue length of the buffer, And a means for notifying congestion between the exchanges by means of a congestion notification cell according to the detection result of the detecting means, and the subscriber exchange accommodating the transmitting terminal extracts the RM cell transmitted from the transmitting terminal. And a means for writing the cell transfer rate information to this RM cell according to the presence / absence information of the detecting means or the presence / absence information of the congestion by the notifying means and returning it to the transmitting terminal. The receiving terminal is accommodated. The subscriber exchange switches the means for generating an RM cell, the means for transmitting this RM cell to this receiving terminal, and the means for folding from this receiving terminal. Means for extracting the generated RM cell, means for transmitting a cell to the receiving terminal according to the cell transfer rate information of the receiving terminal written in the RM cell, and means for transmitting the cell to the receiving terminal according to the cell transfer rate information. It is provided with means for determining the presence or absence of congestion, and means for generating the congestion notification cell according to the determination result of this determining means.

Thus, on the one hand, the speed explicit method is realized, and on the other hand, by using the subscriber exchange which functions as an interface for realizing the congestion notification control method, the speed explicit method is realized in one network. The congestion notification control method can be mixed. By applying the two different methods while making the best use of their respective advantages, efficient information transfer can be performed while maintaining a simple configuration. It is desirable that each of the above means is provided for each virtual channel.

A second aspect of the present invention is a subscriber exchange used in this ATM communication network.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION

[0019]

DETAILED 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.

The present invention is an ATM communication network, and is provided with a transmission section 74 as a means for transmitting an RM cell and transmitting the cell in accordance with the cell transfer rate information written in the RM cell received back. A transmitting terminal 4, a receiving terminal 8 having a receiving section 78 as a means for receiving an RM cell, writing cell transfer rate information in the RM cell in accordance with its own free band information, and sending back the RM cell.
The relay network 2 is provided between the receiving terminal 8 and the transmitting terminal 4, and the relay network 2 is a virtual two-member switchboard in which the transmitting terminal 4 and the receiving terminal 8 are accommodated. The transmitting terminal 5, the virtual receiving terminal 7, and the transit exchange 6
It is an ATM communication network equipped with.

The feature of the present invention is that the virtual transmission terminal 5, the virtual reception terminal 7 and the transit exchange 6 are
Line-corresponding buffer units 22, 32, 4 for temporarily storing cells
2, the congestion determination units 24, 40, 44 as means for detecting the presence or absence of congestion according to the queue lengths of the line corresponding buffer units 22, 32, 42, and the congestion determination unit 2
Congestion notification cell extraction units 28, 31 and congestion notification cells as means for notifying congestion among the virtual transmission terminals 5, virtual reception terminals 7, and transit exchanges 6 according to the detection results of 4, 40, and 44. Generators 35, 45,
The virtual transmission terminal 5 includes the congestion notification cell insertion units 37 and 47, and the virtual transmission terminal 5 detects the presence or absence of congestion in the RM cell extraction unit 21 as a unit that extracts the RM cell transmitted from the transmission terminal 4 and the congestion determination unit 24. The virtual reception terminal 7 is provided with an RM cell insertion unit 27 as a means for writing cell transfer rate information in this RM cell according to the congestion presence / absence information by the notification cell extraction unit 28 and returning it to the transmission terminal 4. An RM cell generation unit 36 as means, an RM cell insertion unit 34 as means for sending this RM cell to the receiving terminal 8, and an RM cell extraction as means for extracting the RM cell returned from this receiving terminal 8. And a buffer control unit 33 as means for transmitting a cell to this receiving terminal according to the cell transfer rate information of this receiving terminal 8 written in this RM cell. A congestion determination unit 40 as a unit for determining the presence / absence of congestion of the receiving terminal 8 according to the cell transfer rate information, and a congestion notification as a unit for generating the congestion notification cell according to the determination result of the congestion determination unit 40. The cell generator 35 is provided. The respective units are provided for each virtual channel.

[Principle of the Present Invention] Here, the principle of the present invention will be described with reference to FIG. FIG. 2 is a conceptual diagram for explaining the principle of the present invention.

In the present invention, the subscriber exchange is used as the virtual transmission terminal 5
Alternatively, the virtual receiving terminal 7 is used, and the functions required for the speed explicit method are provided only in the subscriber exchange. The present invention relates to the transmitting terminal 4
And the virtual transmission terminal 5, between the virtual transmission terminal 5 and the virtual reception terminal 7, and between the virtual reception terminal 7 and the reception terminal 8 by dividing the three cell flow control areas, the transmission terminal 4 and the reception terminal 8 are divided. The cell flow control between the virtual transmission terminal 5 and the virtual reception terminal 7 is performed without depending on the cell flow control method of.

By providing the virtual transmission terminal 5 with means (a) for transmitting the speed notification cell and means (b) for calculating the notification speed, the transmission side subscriber line can control the cell flow by the speed explicit method. To do.

According to the present invention, the virtual transmission terminal 5 is provided with the means (c) for receiving the congestion notification signal, so that the trunk line controls the cell flow by the congestion notification. It is also possible to perform cell flow control using the speed obtained by the means (b) for calculating the notification speed (z).

According to the present invention, the virtual receiving terminal 7 is provided with means (f) for receiving a speed notification cell and means (g) for transmitting a cell to the receiving terminal at a speed not higher than the notification speed. Then, the cell flow control is performed by the speed explicit method.

According to the present invention, the virtual transmission terminal 5 is provided with a means for changing the speed at which the transmission terminal 4 is notified when the congestion notification is triggered, so that a different cell flow control method can be used for the transmission side subscriber line and the relay line. Even when it is adopted, smooth cell flow control is possible in the whole between the transmitting terminal 4 and the receiving terminal 8.

According to the present invention, by using the congestion notification triggered by monitoring the queue length of the counter in the transit exchange 6 (e), the traffic exchange observation, speed calculation, and speed notification signal transmission / reception functions of the transit exchange 6 are significantly increased. It can be simplified.

According to the present invention, the virtual receiving terminal 7 is provided with means for judging congestion from the queue length of the buffer or the cell arrival rate,
A means for transmitting a congestion notification signal is provided to enable cell flow control by congestion notification on the trunk line.

According to the present invention, the virtual receiving terminal 7 has a buffer for each subscriber and monitors the queue length or the cell arrival rate, so that the virtual receiving terminal 7 calculates the speed from the speed notification cell of the receiving terminal 8. Even if it does not, by predicting the congestion of the receiving side subscriber line, smooth cell flow control is possible even when different cell flow control systems are adopted for the receiving side subscriber line and the trunk line.

According to the present invention, when there is a congestion notification from the relay network in the transmitting side subscriber exchange, the cell transfer to the relay network is regulated and at the same time the transmission speed is explicitly notified to the transmitting terminal 4. , A congestion notification type relay network,
Connects to the transmission side subscriber network of the speed explicit method.

In addition, in the receiving side subscriber exchange, when the transmission speed is explicitly notified from the receiving terminal 8, cells are transmitted according to the notified speed, but the transmission buffer does not depend on the notified speed. The congestion of the receiving side subscriber line is predicted from the queue length or the cell arrival rate of the sending buffer, and the congestion is notified to the sending side subscriber exchange. Connect the subscriber network.

Next, an embodiment of the present invention will be described with reference to FIGS. 1 and 3 to 5. In FIG. 1, a virtual transmission terminal 5 is provided between the transmission side subscriber network 1 and the relay network 2. Further, a virtual receiving terminal 7 is provided between the relay network 2 and the receiving side subscriber network 3.
Is provided. The virtual transmission terminal 5 and the virtual reception terminal 7 are subscriber exchanges. Although a plurality of virtual channels are connected to the virtual transmission terminal 5, the transit exchange 6, and the virtual reception terminal 7,
In the embodiment of the present invention, a case where one virtual channel is connected will be described for the sake of easy understanding. The subscriber exchange has both the functions of the virtual receiving terminal 5 and the virtual transmitting terminal 7 in order to perform bidirectional cell transfer. However, in the embodiment of the present invention, only the unidirectional cell transfer is performed for the sake of clarity. explain.

The data cell 9 is transferred from the transmission terminal 4 to the reception terminal 8 via the virtual transmission terminal 5, the transit exchange 6, and the virtual reception terminal 7 on the virtual channel. Receiving terminal 8
The RM cell 12 describing the receivable cell transfer rate is transferred to the virtual receiving terminal 7 at a constant cycle. The virtual receiving terminal 7 reads the value described in the RM cell 12 and transmits the data cell 9 to the receiving terminal 8 at a speed equal to or lower than the value.
The virtual receiving terminal 7 determines congestion when the number of cells accumulated in the line corresponding buffer unit 22 exceeds a predetermined threshold value, and transmits the congestion notification cell 11 to the virtual transmitting terminal 5.

Alternatively, the virtual receiving terminal 7 determines congestion when the number of cells arriving at the line corresponding buffer unit 22 at a certain fixed time interval exceeds a predetermined threshold value,
It is also possible to transmit the congestion notification cell 11 to the virtual transmission terminal 5.

Alternatively, the virtual receiving terminal 7 is the transit exchange 6
When the congestion notification signal is received from the congestion notification cell 1
1 can be sent back.

When the number of cells accumulated in the line-corresponding buffer unit 22 exceeds a predetermined threshold value, the transit exchange 6 determines that there is congestion and sends the congestion notification cell 11 to the virtual receiving terminal 7 or the virtual transmitting terminal 5. To do.

When the virtual sending terminal 5 receives the congestion notification cell 11 from the virtual receiving terminal 7, the virtual sending terminal 5 stops the transmission of the cell toward the virtual receiving terminal 7.

Alternatively, the virtual transmission terminal 5 is the transit exchange 6
When the congestion notification cell 11 is received from, the transmission of the cell toward the transit exchange 6 is stopped.

When the congestion notification cell is received, the virtual transmission terminal 5 decreases the speed of notifying the transmission terminal 4 and writes the speed in the RM cell 10 and transmits the speed to the transmission terminal 4.

The transmitting terminal 4 reads the speed from the RM cell 10 received from the virtual transmitting terminal 5 and transmits the cell at a speed not higher than the notified speed.

If the virtual transmission terminal 5 does not receive the congestion notification for a certain period of time or more, the virtual transmission terminal 5 increases the speed described in the RM cell 10 and transmits it to the transmission terminal 4.

Next, the virtual transmission terminal 5 will be described with reference to FIG. FIG. 3 is a block diagram of the virtual transmission terminal.
The virtual transmission terminal 5 includes an RM cell extraction unit 21, a line corresponding buffer unit 22 provided for each subscriber line, and a buffer control unit 2
3, a congestion determination unit 24, an RM cell generation unit 25, a speed calculation unit 26, an RM cell insertion unit 27, a congestion notification cell extraction unit 28, and a table 29.

The table 29 stores the VPI / VCI of the connected virtual channel, the pointer indicating the cell position in the line corresponding buffer unit 22, the information on the congestion state, and the current speed.

When the RM cell extraction unit 21 receives a cell from the transmission terminal 4, the payload type and protocol I
D is read, and if it is an RM cell, it is extracted, and if it is not an RM cell, it is transferred to the line corresponding buffer unit 22.

The line-corresponding buffer unit 22 has a table 29.
, And stores cells for each virtual channel.

The buffer control unit 23 refers to the table 29, stops the cell transmission of the virtual channel in the congested state, and selects and transmits only the cell of the virtual channel not in the congested state.

The congestion determination unit 24 is a congestion notification cell extraction unit 28.
The congestion state of the table 29 is set or released based on the notification from.

When receiving a cell, the congestion notification cell extraction unit 28 extracts a congestion notification cell, notifies the congestion determination unit 24 of the congestion, and transfers it to the RM cell insertion unit 27 if it is not the congestion notification cell.

When the congestion determination unit 24 is notified of the congestion, it notifies the speed calculation unit 26 of the congestion, and sets the corresponding virtual channel in the table 29 to the congestion state.

The rate calculator 26 calculates the notification rate for each virtual channel and notifies the RM cell generator 25 of the notification rate.

Next, an example of the calculation method of the speed calculator 26 will be described with reference to FIG. FIG. 4 is a flowchart showing the calculation method of the speed calculation unit 26. The present invention is not limited to the calculation method shown in FIG.

When a congestion notification is received from the congestion determination unit 24 (S1), a value obtained by dividing the current speed by the deceleration parameter is subtracted from the current speed (S2). However, if the speed after calculation is less than the predetermined minimum speed (S3),
The minimum speed is set (S4). The speed calculation unit 26 is provided with a timer for each virtual channel, and when there is no congestion notification (S1), the timer is checked, and if the value of the timer is less than the calculation cycle, the operation ends (S5). If the value of the timer is equal to or longer than the calculation cycle (S5), the value obtained by dividing the peak speed by the acceleration parameter is added to the current speed (S6). However, if the calculated speed is higher than a predetermined peak speed (S7), the peak speed is set (S8).
The speed calculator 26 uses the calculated speed as the RM cell generator 25.
(S9), and the timer is reset (S10).

The RM cell inserting section 27 is provided with a counter for each virtual channel, counts the cells transferred from the congestion notification cell extracting section 28 for each virtual channel, and the counter is equal to or larger than a predetermined number of cells. Then, it issues an RM cell generation request to the RM cell generation unit 25.

In the RM cell generation unit 25, when there is a request for RM cell generation from the RM cell insertion unit 27, the table 29 is referred to, the notification speed is described in the RM cell, and the RM cell insertion unit 27 issues the notification speed. Insert.

Next, the virtual receiving terminal 7 will be described with reference to FIG. FIG. 5 is a block diagram of the virtual receiving terminal 7. The virtual receiving terminal 7 includes a congestion notification cell extraction unit 31, a line corresponding buffer unit 32 provided for each subscriber line, a buffer control unit 33, an RM cell insertion unit 34, a congestion notification cell generation unit 35, and an RM. The cell generation unit 36, the congestion notification cell insertion unit 37, the RM cell extraction unit 38, and the table 39.

The table 39 stores the VPI / VCI of the connected virtual channel, the pointer indicating the cell position in the line corresponding buffer unit 32, and the current speed.

When receiving a cell, the congestion notification cell extraction unit 31 extracts a congestion notification cell and transfers it to the congestion notification cell generation unit 35, and transfers it to the line corresponding buffer unit 32 when it is not a congestion notification cell. .

The line-corresponding buffer section 32 has a table 39.
Cells are stored for each virtual channel by referring to. The buffer control unit 33 refers to the table 39 and outputs cells at the current speed.

Further, the buffer control unit 33 monitors the number of cells accumulated for each virtual channel, and when the number of cells accumulated for each virtual channel exceeds a predetermined threshold value, the congestion notification is issued. Cell generator 35
To the VPI / VCI of the corresponding virtual channel.

Alternatively, the buffer control unit 33 monitors the number of cells arriving at a certain fixed time interval for each virtual channel, and when the number of cells arriving at the certain fixed time interval exceeds a predetermined threshold, The congestion notification cell generation unit 35 is notified to the VPI / VCI of the corresponding virtual channel.
It is also possible to notify.

In the RM cell inserting section 34, the number of cells output from the line corresponding buffer section 32 is counted for each virtual channel, and when the counter reaches or exceeds a predetermined fixed number of cells, the RM cell generating section 36 receives the RM cell. Issue a cell generation request.

In the RM cell generator 36, the RM cell inserter 3
4, the RM cell insertion unit 34 inserts the RM cell when the RM cell generation request is issued. Table 39 at this time
It is also possible to describe the current speed in the RM cell with reference to.

When the RM cell extracting unit 38 receives a cell from the receiving terminal 8, if the cell is an RM cell, the RM cell extracting unit 38 extracts the RM cell and writes the speed described in the RM cell in the table 39.

Alternatively, when the RM cell extracting unit 38 receives a cell from the receiving terminal 8, if it is not an RM cell, the RM cell extracting unit 38 transfers it to the congestion notification cell inserting unit 37.

When there is a congestion notification from the congestion notification cell extraction unit 31 or the buffer control unit 33, the congestion notification cell generation unit 35 immediately generates a congestion notification cell and transmits it from the congestion notification cell insertion unit 37.

[0067]

As described above, according to the present invention,
The speed explicit method and the congestion notification control method can be mixed in one network. As a result, efficient information transfer can be performed while maintaining a simple configuration. That is, it becomes possible to connect the terminal of the speed explicit method to the existing network of the congestion notification method. Further, in the transit exchange, the function for the speed explicit method can be omitted, and the effect of reducing the network cost can be obtained.

[Brief description of 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 conceptual diagram for explaining the principle of the present invention.

FIG. 3 is a block diagram of a virtual transmission terminal.

FIG. 4 is a flowchart showing a calculation method of a speed calculation unit.

FIG. 5 is a block diagram of a virtual receiving terminal.

FIG. 6 is a diagram showing a speed explicit method.

[Explanation of symbols]

 1 sending side subscriber network 2 relay network 3 receiving side subscriber network 4 sending terminal 5 virtual sending terminal 6 transit exchange 7 virtual receiving terminal 8 receiving terminal 9 data cell 10, 12, 87 RM cell 11 congestion notification cell 21, 38 RM Cell extraction unit 22, 32, 42 Line-corresponding buffer unit 23, 33 Buffer control unit 24, 40, 44 Congestion determination unit 25 RM cell generation unit 26 Speed calculation unit 27, 34 RM cell insertion unit 28, 31 Congestion notification cell extraction unit 29, 39 Tables 35, 45 Congestion notification cell generator 36 RM cell generator 37, 47 Congestion notification cell inserter 74 Transmitter 78 Receiver 82, 84 Subscriber switch 83 Transit switch

Claims (3)

[Claims] 1. A transmission terminal equipped with means for transmitting an RM cell and transmitting the cell in accordance with the cell transfer rate information written in the RM cell received back, and an empty band of its own receiving the RM cell. A receiving terminal provided with means for writing cell transfer rate information in the RM cell according to the information and returning the RM cell for returning; and a relay network interposed between the receiving terminal and the transmitting terminal. In this ATM network, which includes two subscriber exchanges each accommodating the transmitting terminal and the receiving terminal, and a relay exchange, the subscriber exchange and the relay exchange temporarily store cells. A buffer for accumulating is provided, and means for detecting the presence or absence of congestion according to the queue length of this buffer and mutual exchange between the exchanges according to the detection result of this detecting means. And a means for notifying congestion by a congestion notification cell, the subscriber exchange accommodating the transmitting terminal, means for extracting the RM cell sent from the transmitting terminal, and the presence or absence of congestion of the detecting means or the Means for writing cell transfer rate information in the RM cell according to the presence / absence information of the congestion by the means for notifying and returning to the transmitting terminal, the subscriber exchange accommodating the receiving terminal, means for generating an RM cell, and Means for sending an RM cell to this receiving terminal, means for extracting an RM cell returned from this receiving terminal, and a cell for this receiving terminal according to the cell transfer rate information of this receiving terminal written in this RM cell To determine whether there is congestion at the receiving terminal according to the cell transfer rate information, and the determination result of this determining means. ATM communication network, comprising the means for generating said congestion notification cell I. 2. The ATM communication network according to claim 1, wherein each of the means is provided for each virtual channel. 3. A subscriber exchange used in the ATM communication network according to claim 1.