JPH1065678A - Atm exchange system and its traffic control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the occurrence of a congestion in an ATM(asynchronous transfer mode) exchange, to increase valid throughput and to ensure the justice of throughput between VC (logic channel) using the same output line. SOLUTION: An ATM exchange system comprises a core switch part 40 having an ATM cell exchange function among high speed input/output ports, extension input buffer module parts 50 multiplexing a plurality of low speed input lines 91 to high speed input ports 71 and extension output buffer module parts 60 separating outputs from the high speed output ports 72 into a plurality of low speed output lines 93. The extension input buffer module parts 50 can execute queuing for the respective output ports and for respective service classes. The extension output buffer module parts 60 can execute queuing for the respective output lines which they store and for the respective service classes. The core switch part 40 emits a back pressure signal 101 and the extension output buffer module parts 60 emit back pressure signals 102 and 103.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ATM (Asynchro
nous Transfer Mode: As for an ATM switching system for switching cells (hereinafter sometimes simply referred to as "cells") between input and output lines,
The present invention relates to an exchange configuration method capable of easily increasing an exchange capacity, a traffic control method of an ATM exchange system capable of suppressing congestion occurrence, increasing an effective throughput, and achieving throughput fairness between logical channels (VCs). .

[0002]

2. Description of the Related Art In a conventional small-scale ATM switching system with a switching capacity of about 2.4 Gbps, as shown in FIG. The simple input / output buffer format to be accommodated is the mainstream.

A first conventional ATM switching system shown in FIG. 29 comprises a core switch unit 40 'and first to M-th input buffer module units 80-1, 80-2, 80-.
3,..., 80-M. The first to M-th input buffer module units 80-1 to 80-M respectively include first to M-th input lines 91-1, 91-2, 91-3,
, 91-M and the first to M-th intermediate lines 92-1, 9
2-2, 92-3,..., 92-M.
The core switch unit 40 'includes first to Mth intermediate lines 92.
-1 to 92-M and first to M-th output lines 93-1, 9
, 93-3,..., 93-M.
First to M-th input lines 91-1 to 91-M, first to M-th intermediate lines 92-1 to 92-M, and first to M-th output lines 93-1 to 93-M Is 155 Mb
It has a transmission speed of ps.

As shown in FIG. 30, each input buffer module section 80 (subscripts omitted) includes first to fourth service class units 81-1, 81-2, 81-3, 81-.
4 and the class connected to the input line 91 (subscript omitted)
It is composed of a line-by-line separator 82, an inter-class priority control unit 83, and a back pressure receiving unit 84. The first to fourth service class units 81-1 to 81-4 are:
It is arranged between the class / line-specific separator 82 and the inter-class priority control unit 83. The first to fourth service class units 81-1 to 81-4 serve as input buffers.

Here, the first to fourth services (traffic classes) provided by the first to fourth service class units 81-1 to 81-4 are respectively a constant bit rate service (Constant Bit Rate Service).
: CBR), Variable Bit Rate Service (Variable Bi
t Rate Service: VBR), Available Bit Rate Service (ABR),
And Unspecified Bit Rate Service
Rate Service: UBR). The constant bit rate service (CBR) is used for a real-time video / audio service and a circuit switching emulation service, and information is transmitted at a constant bit rate. The variable bit rate service (VBR) targets real-time variable-rate video and audio, and can support a non-real-time data communication service whose rate can be specified in advance, such as a free service in a public network. Available bit rate service (A
BR) is a service that applies to most currently existing LAN applications. TCP / IP (Tras
When accommodating an existing data application such as mission control protocol / Internet Protocol), the available bit rate service transfers data without making a bandwidth reservation. In the available bit rate service, if the link is empty, the entire available link band can be used by one connection, but when the link comes in, the rate is automatically reduced and transferred. Unspecified bit rate service (UBR), like ABR, has a peak rate PC
Although only R declares at the time of connection setting, there is no bandwidth allocation, and no input control other than PCR is performed. Therefore, there is no quality assurance rule for unspecified bit rate services.

First to fourth service class units 8
Since 1-1 to 81-4 have the same configuration, only the first service class unit 81-1 will be described below. The first service class unit 81-1 includes:
M output line correspondence queues 88 corresponding to the first to Mth output lines 93-1 to 93-M, and a rotation priority control unit 89
It is composed of The input end of each output line corresponding queue 88 is connected to the class / line separator 82, and the output end is connected to the input end of the rotation priority control unit 89. An output terminal of the rotation priority control unit 89 is connected to an input terminal of the inter-class priority control unit 83.

[0007] As shown in FIG.
′ Are the first to M-th core switch queues 41 corresponding to the first to M-th output lines 93-1 to 93-M, respectively.
, 41-2, 41-3,..., 41-M; Time division multiplex bus 42
Are the first to N-th intermediate lines 92-1 to 92-M and the first
To the M-th core switch queues 41-1 to 41-M. 1st to Mth core switch queue 4
1-1 to 41-M are first to M-th output lines 9, respectively.
3-1 to 93-M. The first to M-th core switch queues 41-1 to 41-M serve as output buffers.

The cell switching operation of the first conventional ATM switching system will be described below with reference to FIGS. The ATM cells flowing from the input line 91 (subscript omitted) are separated by the class / line separator 82 into ATM cells.
After the destination output line of the cell and the service class type are identified, they are stored in an appropriate output line corresponding queue 88.
The rotation priority control unit 89 can rotate the cell transmission right between the output line corresponding queues 88 belonging to the same service class in a circular manner. The inter-class priority control unit 83 controls competition of cell transmission requests between different service classes according to a predetermined priority control logic. The ATM cells extracted from the output line corresponding queue 88 selected by the combination processing of the rotation priority control unit 89 and the inter-class priority control unit 83 are transferred to the intermediate line 92 (subscript omitted) and the time division multiplex bus 4.
2 is stored in the core switch queue 41 (subscript omitted) corresponding to the destination output line. In the core switch queue 41, the cells are transmitted to the output line 93 (subscript omitted) in order from the first cell. The buffer occupancy counting unit 43 in the core switch unit 40 ′ observes the queue length of the core switch queue 41. The back pressure transmission unit 44 is provided with the core switch queue 4 held by the buffer occupancy counting unit 43.
1 and detects that there is a core switch queue 41 in which the queue length exceeds the threshold value and is in a congested state, all the input buffer module units 8
A back pressure signal 101 indicating an output line in a congested state is transmitted for 0. The back pressure receiving unit 84 in the input buffer module unit 80 specifies the output line that has issued the back pressure signal 101 from the information of the received back pressure signal 101, and outputs a cell from the output line corresponding queue 88 corresponding to the output line. The line priority control unit 89 is notified to prohibit the transmission.

As described above, the traffic control between the input and output buffers in the first conventional ATM switching system is performed in order to prevent the loss of ATM cells in the output buffer when a specific output line is congested. There is only a simple back pressure control, such as generating a back pressure signal 101 for all input buffers to stop outputting cells to the line.

The above-mentioned first conventional ATM switching system has the following problems. In order to increase the switching capacity, it is necessary to accommodate more low-speed line interfaces on a higher-speed time-division multiplex bus.
As the number of input / output signals on the time-division multiplexed bus increases, the number of pins becomes insufficient.

FIG. 32 shows a second conventional ATM switching system in which the switching capacity can be easily increased. ATM shown
The switching system includes a core switch unit 40 ″ and first to Nth extended input buffer module units 50′-1, 50 ′.
'-2, 50'-3, ..., 50'-N, and the first to Nth
Extended output buffer module units 60'-1, 60'-
, 60'-N. In the illustrated example, a plurality of extended input buffer module units and a plurality of extended output buffer module units are provided, but each may be one.

Each of the first to N-th extended input buffer module units 50'-1 to 50'-N has four input lines 9
1 and the first to N-th extended input buffer module units 50'-1 to 50'-N
First to Nth input ports 71-1, 71-2, 71-
3,..., 71-N. Core switch part 4
0 ″ is the first to N-th input ports 71-1 to 71-N
And the first to N-th output ports 72-1, 72-2, 72
-3,..., 72-N. 1st to Nth
Extended output buffer module units 60'-1 to 60'-
N are connected to the four output lines 93, and the first to N-th extended output buffer module units 60'-1
To 60'-N are connected to the first to N-th output ports 72-1 to 72-N, respectively. Each of the input line 91 and the output line 93 has a transmission speed of 155 Mbps, and has an input port 71 (subscript omitted) and an output port 7.
Each of 2 (subscript omitted) has a transmission speed of 620 Mbps.

The core switch unit 40 "has an ATM switching function between high-speed input / output ports. Each extended input buffer module unit 50 '(subscript omitted) has a plurality (four in this example) of low-speed input lines. 91 is multiplexed to mediate connection to the high-speed input port 71 (subscript omitted) of the core switch unit 40 ″, and queuing can be performed for each output port.
Each extended output buffer module unit 60 '(subscript omitted)
Plays a role of separating the output from the high-speed output port 72 (subscript omitted) of the core switch unit 40 ″ into a plurality of (four in this example) low-speed output lines 93, and performs queuing for each output line. ATM cells can be queued for each destination output line and for each service class in each extended input buffer module unit 50 '. In each extended output buffer module unit 60', the ATM cells can also be queued for the destination output line. Queuing is possible for each service class.

As shown in FIG. 33, each extended input buffer module unit 50 '(subscripts omitted) includes first to fourth service class units 51-1, 51-2, 51-.
3, 51-4, a class / port-specific separator 52 connected to four input lines 91, and an inter-class priority control unit 53
, A back pressure receiving unit 54 ′, a buffer occupancy counting unit 55, a packet reception control unit 56, and a resource management (hereinafter abbreviated as RM) cell processing unit 57. First to fourth service class units 51
-1 to 51-4 are arranged between the class / port-specific separator 52 and the inter-class priority control unit 53. The first to fourth service class units 51-1 to 51-4 are:
For the first to fourth service classes that provide a constant bit rate service (CBR), a variable bit rate service (VBR), an available bit rate service (ABR), and an unspecified bit rate service (UBR), respectively. is there. The first to fourth service class units 51-1 to 51-4 serve as input buffers.

First to fourth service class units 5
Since 1-1 to 51-4 have the same configuration, only the first service class unit 51-1 will be described below. The first service class unit 51-1 includes:
It comprises N output port correspondence queues 58 corresponding to the first to Nth output ports 72-1 to 72-N, and a rotation priority control section 59. Queue 58 for each output port
Is a virtual source queue 58-1 and a rate control unit 58-
2 and a virtual switch internal queue 58-3. The input end of each virtual source queue 58-1 has a class /
The output terminal of the virtual switch internal queue 58-3 is connected to the port-specific separator 52 via the rate control unit 58-2.
Is connected to the input terminal of Virtual switch internal queue 5
The output terminal of 8-3 is connected to the input terminal of the rotation priority control section 59. That is, the output port corresponding queue 58 is a virtual source queue 58 that sandwiches the rate control unit 58-2.
-1 and a virtual switch internal queue 58-3. An output terminal of the rotation priority control unit 59 is connected to an input terminal of the inter-class priority control unit 53.

By providing the output port corresponding queue 58 for each service class, a multi-service class environment can be easily provided. The buffer occupancy amount counting unit 55 outputs a logical channel (V
C) Observe the buffer occupancy for each. The packet reception control unit 56 controls packet selection and discard based on the measured buffer occupancy. The RM cell processing unit 57
ER (Explicit Rat) to backward RM cell of class
e) Write the value.

As shown in FIG. 34, the core switch section 40 "includes first to N-th output ports 72-1 to 72-.
, 41-N, the time division multiplexed bus 42, the buffer occupancy count unit 43, and the back pressure And a transmitting unit 44. The time division multiplex bus 42 includes first to Nth input ports 71-1 to 71-
N and first to Nth core switch queues 41-1 to 41-1
-N. The first to N-th core switch queues 41-1 to 41-N are connected to the first to N-th output ports 72-1 to 72-N, respectively. The first to N-th core switch queues 41-1 to 41-N serve as intermediate buffers.

As shown in FIG. 35, each extended output buffer module unit 60 '(subscripts omitted) includes first to fourth
Service class units 61-1, 61-2, 61-
3, 61-4, a class / line-specific separator 62 connected to an input port 72 (subscript omitted), and four output lines 93
, A buffer occupancy measuring unit 65, an acceptable rate calculating unit 66,
And an M cell processing unit 67. The first to fourth service class units 61-1 to 61-4 include a class /
It is arranged between the line separator 62 and the inter-class priority control unit 63. The first to fourth service class units 61-1 to 61-4 respectively include a fixed bit rate service (CBR) and a variable bit rate service (VB
R), available bit rate service (ABR),
And the first to fourth service classes that provide unspecified bit rate service (UBR). The first to fourth service class units 61-1 to 61-4 serve as output buffers.

First to fourth service class units 6
Since 1-1 to 61-4 have the same configuration, only the first service class unit 61-1 will be described below. The first service class unit 61-1 includes:
It comprises four output line queues 68 corresponding to the four output lines 93. The input terminal of each output line corresponding queue 68 is connected to the class / line separator 62, and the output terminal is connected to the input terminal of the corresponding inter-class priority control unit 63.

Like the extended input buffer module unit 50 ', the extended output buffer module unit 60' can easily provide a multi-service class environment by preparing an output line corresponding queue 68 for each service class. . The receivable rate calculator 66 is the first of the virtual queues (global queues) of the set of output port corresponding queues 58 addressed to the same port among the output port corresponding queues 58 existing in all the extended input buffer module units 50 '. And the second acceptable rate in the output line corresponding queue 68 existing in the extended output buffer module unit 60 '.

The extended output buffer module section 60 'uses a completely shared buffer system in which each logical queue can freely use the entire buffer capacity prepared for each module. In the extended input buffer module unit 50 ', an upper limit is set for each logical queue so that a specific logical queue cannot monopolize the entire buffer capacity.

The cell switching operation of the second conventional ATM switching system will be described below with reference to FIGS. In the extended input buffer module unit 50 '(subscript omitted) accommodating a plurality of input lines 91,
The ATM cell flowing from the input line 91 is stored in the appropriate output port corresponding queue 58 after the destination output port and the service class type of the ATM cell are identified by the class / port separator 52. Output port corresponding queue 58
Is composed of the virtual source queue 58-1, the rate control unit 58-2, and the virtual switch internal queue 58-3, as described above. The ATM cell is first stored in the virtual source queue 58-1, but moves from the virtual source queue 58-1 to the virtual switch internal queue 58-3 at the transfer rate provided by the rate control unit 58-2. The rotation priority control unit 59 circulates the cell transmission right between the virtual switch internal queues 58-3 belonging to the same service class. The inter-class priority control unit 53 controls competition of cell transmission requests between different service classes according to a predetermined priority control logic. By the combination process of the rotation priority control unit 59 and the inter-class priority control unit 53, the data is stored in the core switch queue 41 (subscript omitted) corresponding to the destination output port 72 (subscript omitted).

In the core switch queue 41, ATM cells are sent out to the output port 72 in order from the first cell, and sent to the subsequent extended output buffer module unit 60 '(subscript omitted).

In the extended output buffer module unit 60 ', the destination output line of the ATM cell and the service class type are identified by the class / line-specific separator 62 and stored in an appropriate output line corresponding queue 68. The inter-class priority control unit 63 prepared for each output line determines in advance the service class to which the next cell is to be transmitted from the output line correspondence queue 68 of each service class that stores cells destined for the same output line. Selected according to the priority control logic
The head cell is transmitted to the output line 93.

In the second conventional ATM switching system having such a configuration, the core switch queue 41 (subscript omitted) prepared for each output port 72 (subscript omitted) in the core switch unit 40 "has the same queue length. When the threshold value is exceeded, the back pressure transmitting section 44 transmits the back pressure signal 101 to all the extended input buffer module sections 5.
It only occurs at 0 '(subscript omitted). Further, each extended output buffer module unit 60 '(subscript omitted) does not perform back pressure control, but only performs cell discarding.

In the configuration of the second conventional ATM switching system, the extended output buffer module unit 60 '
Output buffer cannot be used effectively. As traffic control between input / output buffers in the second conventional ATM switching system having such a configuration, when a specific output line is congested, the output line is controlled to prevent cell loss in the output buffer. There is only a simple back pressure control, such as generating a back pressure signal for all input buffers to instruct the cell output to stop.

[0027]

The first and second conventional ATM switching systems have the following common problems. Congestion frequently occurs due to simultaneous arrival of ATM cells from a plurality of input lines to the same output line, and accordingly, a back pressure signal for preventing cell loss in an output buffer is frequently transmitted. Basically, the back pressure control has the effect of equalizing the throughput from each input line to the same output line. If the number of logical channels (VCs) going to the same output line varies among the input lines, the same is applied. In the first and second conventional ATM switching systems, such a problem of non-equity of throughput arises due to frequent generation of a back pressure signal, such as no guarantee of fairness in throughput between VCs using output lines. .

An object of the present invention is to provide an ATM switching system which suppresses the occurrence of congestion inside the ATM switching system, increases the effective throughput, and guarantees the fairness of the throughput between VCs using the same output line, and its traffic. It is to provide a control method.

[0029]

An AT to which the present invention is applied
The M-switching system comprises a core switch unit having an output buffer type configuration having an ATM switching function between a high-speed input port and a high-speed output port, and an A switch from a plurality of low-speed input lines.
It has at least one extended input buffer module unit for multiplexing TM cells to a high-speed input port, and at least one extended output buffer module unit for separating an output from a high-speed output port into a plurality of low-speed output lines.
The extended input buffer module unit enables queuing for each output port and service class of the core switch unit, and the extended output buffer module unit enables queuing for each output line and service class accommodated by itself. Have.

According to the present invention, in the ATM switching system having the above configuration, back pressure control is performed to prevent cell loss in the core switch unit and the extended output buffer module unit. That is, the core switch unit, when the queue length of the core switch queue prepared for each output port exceeds a predetermined first threshold,
A first back pressure signal is generated for all extended input buffer module units. The extended output buffer module generates a second back pressure signal to the extended input buffer module when the total buffer occupancy exceeds a predetermined second threshold value, and / or When the total buffer occupancy exceeds a predetermined third threshold value, a third back pressure signal is generated to the core switch unit. The extended input buffer module unit stops the cell output to the output port that generates the received first back pressure signal or second back pressure signal. The core switch section is
Cell output to the extended output buffer module that generates the received third buffer pressure signal is stopped.

Further, according to the present invention, the AT having the above configuration
In an M switching system, internal congestion is suppressed from occurring frequently to increase the throughput of each output line, improve the fairness of throughput between VCs using the same output line, and increase the buffer capacity of the extended output buffer module. Perform control to measure effective use. For this purpose, a first acceptable route in a virtual queue (global queue) composed of a set of output port corresponding queues destined for the same port among output port corresponding queues in all extended input buffer module units, and And a rate calculation unit for periodically calculating the second acceptable route in the output line corresponding queue. The output port corresponding queue in the extended input buffer module has a dual configuration of a virtual source queue and a virtual switch internal queue. The cell transfer from the virtual source queue to the virtual switch internal queue is performed by a rate control provided between the virtual source queue and the virtual switch internal queue based on the acceptable rate calculated by the global queue or the output line corresponding queue. Controlled by the unit.

Further, according to the present invention, the AT having the above configuration
In the M-switching system, the buffer occupancy of the queue corresponding to the output port in the extended input buffer module unit is determined for each output line and the logical channel (VC) so that the rate control in the rate control unit in the extended input buffer module unit corresponds to the output line. When the first cell of the packet arrives at the queue corresponding to the output port in the extended input buffer module unit, the buffer occupancy by the destination output line of the packet and the buffer occupancy by the logical channel (VC) are respectively measured. When the threshold value is exceeded, the packet is discarded, and the threshold value to be compared with the buffer occupancy for each output line is determined by the acceptable rate calculated by the output line corresponding queue in the extended output buffer module unit. And the number of active VCs in the output port corresponding queue, To be determined.

Further, according to the present invention, the A
ABR capable of adaptively changing transmission rate according to network congestion in TM exchange system
As the ABR rate control for the class, the receivable rate is calculated by the global queue of the ABR class and the queue corresponding to the output line in the extended output buffer module unit, and AB
The smaller of the receivable rates of the global queue and the output line corresponding queue through which the R class VC passes is described in the backward RM cell transmitted from the receiving terminal of the VC to the transmitting terminal.

[0034]

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

Referring to FIG. 1, an ATM switching system according to an embodiment of the present invention will be described later. Has been changed to Therefore, the extended input buffer module unit, the core switch unit, and the extended output buffer module unit have 50 (subscript omitted), 40,
And 60 (subscript omitted).

In the ATM switching system shown in FIG.
The core switch unit 40 ″ transmits the first back pressure signal 101 to all the extended input buffer module units 50 ′.
(Subscript omitted). On the other hand, in the ATM switching system shown in FIG.
0 not only sends the first back pressure signal 101 to all extended input buffer module units 50,
The extended output buffer module section 60 sends the second and third back pressure signals 102 and 103 to all the extended input buffer module sections 50 and the core switch section 40, respectively. In the present embodiment,
The extended output buffer module unit 60 sends the second and third back pressure signals 102 and 103 to all the extended input buffer module units 50 and the core switch unit 40, respectively. 2 back pressure signal 102
May be sent to all the extended input buffer module units 50, or only the third back pressure signal 103 may be sent to the core switch unit 40.

Referring to FIG. 2, the extended input buffer module section 50 (subscript omitted) is different from that shown in FIG. 33 in that the back pressure receiving section is changed.
It has a configuration similar to that shown in FIG. Therefore,
The reference numeral 54 is assigned to the back pressure receiving unit, and those having the same functions as those shown in FIG. 33 are assigned the same reference numerals, and their explanation is omitted.

The back pressure receiving section 54 transmits the first pack pressure signal 101 to the core switch section 40.
(FIG. 1) as well as the second back pressure signal 102 from the extended output buffer module 6
0 (subscript omitted), and controls the rotation priority control section 59 as described later.

Referring to FIG. 3, the core switch unit 40
Has a configuration similar to that of the core switch unit 40 ″ shown in FIG. 34 except that it has a back pressure receiving unit 45. Therefore, components having the same functions as those shown in FIG. And their description is omitted.

The back pressure receiving section 45 receives the third back pressure signal 103 from the extended output buffer module section 60 (subscript omitted) (FIG. 1), and switches the core switch queue 41 (subscript omitted) as described later. Control.

Referring to FIG. 4, the extended output buffer module section 60 (subscript omitted) has the same configuration as the extended output buffer module section 60 'shown in FIG. . Therefore, components having the same functions as those shown in FIG. 35 are denoted by the same reference numerals, and description thereof will be omitted.

The buffer pressure transmitting section 64 refers to the contents of the buffer occupancy counting section 65 as described later and transmits the second and third pack pressure signals 102 and 103 to all the extended input buffer module sections 50 ( (Subscript omitted) (FIG. 1) and core switch unit 4
Send to 0.

FIG. 5 shows an extended input buffer module section 50.
5 shows an example of the information content (buffer occupancy information table) 200 held by the buffer occupancy counting unit 55 in FIG. The buffer occupancy counting unit 55 in the extended input buffer module unit 50 outputs the queue 5 corresponding to the output port of each service class.
8, the total queue length including the virtual source queue 58-1 and the virtual switch internal queue 58-3, the queue length of the virtual switch internal queue 58-3, and the total queue length per output line /
The buffer occupancy for each VC is retained.

FIG. 6 shows an example of the information content (buffer occupancy information table) 201 held by the buffer occupancy counting unit 43 in the core switch unit 40. Core switch unit 40
The buffer occupancy counting unit 43 in each of the core switch units 4
It has a queue length of 1 (subscript omitted).

FIG. 7 shows the extended output buffer module section 60.
3 shows an example of information contents (buffer occupancy information tables) 202 and 203 held by the buffer occupancy counting unit 65 in FIG. The buffer occupancy counting unit 65 in the extended output buffer module unit 60 includes a buffer occupancy in the output line corresponding queue 61 (subscript omitted) of each service class and each output port constituting a global queue addressed to the extended output buffer module unit 60. Save the corresponding queue length.

[0046]

FIG. 8 is a schematic diagram of back pressure control in an ATM switching system according to the present invention. FIG. 8 illustrates only the first extended input buffer module unit 50-1 and the first extended output buffer module unit 60-1, and the second to Nth extended input buffer module units 5-1.
The illustration of 0-2 to 50-N and the second to N-th extended output buffer module units 60-2 to 60-N is omitted. Also, for simplicity of description, a configuration in a case where only one service class exists will be described. Therefore, the first extended input buffer module unit 50-1 has 1
Only the first service class unit 51 is included, and the first extended output buffer module unit 60-1 includes only one service class unit 61.

In the core switch unit 40, the queue length Q _cs of the core switch queue 41 (subscript omitted) prepared for each output port 72 (subscript omitted) is equal to the first threshold Q
_{When th (bpcs)} is exceeded, the buffer pressure transmitter 44
Indicates the first back pressure signal (BP) to all the extended input buffer module units 50 (subscripts omitted) C
S) Send 101. In each extended input buffer module unit 50, the first back pressure signal (BP C
S) Upon receiving 101, the back pressure receiving unit 54
The first back pressure signal (BP CS) The transmission of cells to the output port that transmitted 101 is stopped. still,
In an environment where a plurality of service classes are mixed, a first threshold value Q _{th (bpcs)} is prepared for each service class, or one back pressure signal (BP) CS) 10
By applying 1 to a plurality of service classes, control according to various service class quality requirements becomes possible.

On the other hand, the extended output buffer module 60
(Subscript omitted), total buffer usage Q_oxbIs the second
Threshold Q_{th (bpoxb low)}If you exceed
The shear transmission unit 64 is provided with all extended input buffer modules.
The second back pressure signal (BP
OXB LOW) 102 is transmitted. Each extended input battery
In the module section 50, the second back pressure
Signal (BP OXB LOW) 102 back pressure
-The receiving unit 54 receives the second back pressure signal (BP
OXB LOW) for the output port that sent 102
Stop sending cells. Second threshold for each service class
Value Q_{th (bpoxb low)}Or a second battery
Pressure signal (BP OXB LOW) 102
By limiting the service classes to be applied, various services can be
Control according to service class quality requirements becomes possible.

The extended output buffer module 60
(Subscript omitted), total buffer usage Q_oxbIs the third
Threshold Q_{th (bpoxb high)}If you exceed
The shear transmission unit 64 is a core switch unit 4 located at the preceding stage.
0 to the third back pressure signal (BP OX
B HIGH) 103 is transmitted. Core switch unit 40
Then, the third back pressure signal (BP OXB
HIGH) The back pressure receiving unit that has received 103
45 is a third back pressure signal (BP OXB
HIGH) subsequent extended output buffer module that sent 103
Cell output to the module 60 is stopped.

As described above, according to the above-described embodiment, in order to realize an ATM switching system having a large switching capacity, the first conventional technique in which a low-speed line interface is directly accommodated in a time division multiplex bus. In the ATM switching system (FIG. 29) and the ATM switching system according to the present invention which directly accommodates a higher-speed port interface, the ATM switching system according to the present invention clearly has a smaller number of interfaces accommodated in the time division multiplex bus.
As a result, it is possible to suppress the occurrence of a problem such as a shortage of pins in LSI mounting.

The extended input buffer module 50
The output port corresponding queue 58 is provided for each service class, and the application of the first and second back pressure signals 101 and 103 transmitted from the core switch unit 40 and the extended output buffer module unit 60 in order to prevent cell discard. By subdividing the service class, it is possible to provide various service class qualities with respect to the cell loss rate and the delay.

FIG. 9 shows an environment for calculating the acceptable rate.
In FIG. 9, as in FIG. 8, only the first extended input buffer module unit 50-1 and the first extended output buffer module unit 60-1 are shown, and only one service class exists for simplification of description. The configuration for the case in which it is not performed will be described.

The receivable rate calculating section 66 installed in each extended output buffer module section 60 (subscript omitted) has its own storage capacity among the output port corresponding queues 58 in all the extended input buffer module sections 50 (subscript omitted). Global queue 90, which is an aggregate of the virtual switch internal queue 58-3 of the output port corresponding queue 58 destined for the output port, and its extended output buffer module 60
Of the line output corresponding queue 68 accommodated in the service class is observed for each service class, and a receivable rate at which the queue length stabilizes with time is periodically calculated based on the change tendency. A switch internal control cell that moves only inside the switch is prepared so that the receivable rate calculation unit 66 installed in each extended output buffer module unit 60 (subscript omitted) can grasp the global queue length. Each extended input buffer module unit 50 describes the output port corresponding queue length and periodically transmits the switch internal control cells. The extended output buffer module unit 60 that receives the switch internal control cell restores the global queue length addressed to the output port from the contents of the switch internal control cell.

The transmission rate setting of the output port corresponding queue 58 in the extended input buffer module unit 50 to the rate control unit 58-2 is executed every time the acceptable rate calculation unit 66 calculates the acceptable rate. The rate control unit 58-of the output port correspondence queue 58 corresponding to the output port of the port number i in a certain extended input buffer module unit 50-
The transmission rate R [i] set to 2 is the acceptable rate ER _g [i] calculated by the global queue 90 of the output port with the port number i and the output port corresponding queue 58
The product of the current total number of active VCs N _vc [i] at
Alternatively, the acceptable rate ER _line calculated in each output line corresponding queue 68 accommodated by the output port of port number i
[I, j] (j is an output line number) and the number of active VCs N _{vc for} each output line in the output port corresponding queue 58
The smaller of the sums of the products [i, j] (where N _vc = ΣN _vc [i, j]) is set. That is,
The transmission rate R [i] is obtained by the following equation (1).

[0055]

(Equation 1) The number of active VCs is calculated with reference to buffer occupancy information for each VC in each output port corresponding queue 58 held by the buffer occupancy counter 55.

As described above, according to the above-described embodiment, the input queue is larger than the output rate and the global queue 90 or the output line corresponding queue 68 in the extended output buffer module unit 60 where the congestion occurs. An acceptable rate at which the utilization rate can be increased without causing congestion is calculated, and the output port corresponding queue 58 in the extended input buffer module unit 50 is changed to the virtual source queue 58-1 and the virtual switch internal queue 58-3. Of the cell transfer rate from the virtual source queue 58-1 to the virtual switch internal queue 58-3 as AT
The control is performed based on the acceptable rate calculated by the rear arrangement module of the M exchange system. As a result, for the unclear input traffic that does not specify the traffic characteristics, which is a major factor causing the internal congestion of the ATM switching system, the virtual source queue 58-
It is possible to temporarily store data in the ATM switch 1 to limit the substantial inflow into the ATM exchange. In addition, it is possible to reduce the frequency of occurrence of internal congestion and remove interference between service classes due to internal congestion.

The cell transfer to the entire output port 72 (subscript omitted) can be controlled, but cannot be controlled for each output line 93 accommodated by the output port 72. Queue 5
8 is multiplied by the acceptable rate calculated by the output line corresponding queue 68 accommodated by the corresponding destination output port by the number of active VCs for each output line in the output port corresponding queue 58. 58-2
Is set in all the extended input buffer module units 50. Thereby, even when the number of VCs to the same output line varies among the extended input buffer module units 50, each extended input buffer module unit 50 autonomously determines the transmission rate in consideration of the VC number for each output line. Therefore, it is possible to guarantee an even throughput between VCs going to the same output line.

Next, the relationship between ATM cells and packets will be described. As is well known, the communication protocol is hierarchical, and each layer drops an identifiable information block to a lower layer and requests transmission. The uppermost protocol layer is the application layer, and the lower protocol layer has an ATM layer.
There are various intermediate protocol layers between the TM layer.

First, the application layer generates a transmission request and passes the data to the lower intermediate protocol layer. The intermediate protocol layer passes it to the ATM layer after special processing (segment header / trailer addition) in that layer. The ATM layer divides the dropped information block of the intermediate protocol layer into a fixed length (53 bytes) called an ATM cell and attempts transmission of each ATM cell. Here, the information block of the intermediate protocol layer corresponds to a packet. Therefore, the packet is divided into a plurality of ATM cells. In other words, a packet is composed of a plurality of ATM cells.

In the upper protocol layer, since processing is performed on a packet basis, it is indifferent to how many ATM cells constituting the packet have dropped. In short, it is important for the upper protocol layer whether the whole packet is transmitted or not. The packet selection and discarding is a method of identifying a cell group belonging to the same packet from individual cell information and discarding the cell in packet units.

Next, with reference to FIG. 10, a description will be given of the packet selection and discarding process by the packet reception control unit 56 in the extended input buffer module unit 50 (subscript omitted). The packet reception control unit 56 determines that the first cell of the packet is the output port corresponding queue 5 corresponding to the output port of the port number i in a certain extended input buffer module unit 50.
8 (step F1), the fixed threshold Q _th set for the entire queue and the acceptable rate ER _line [i for each output line accommodated in the output port 72-i of the port number i. , J] (j is the output line number) and the number of active VCs N _vc [i, j] for each output line in the output port corresponding queue 58, as shown in the following equation 2, the threshold value Q _{th (line) )} Is calculated (step F2).

[0062]

(Equation 2) Here, A is the destination output line number of the packet. The packet reception control unit 56 causes the buffer occupancy counting unit 55 to occupy Q _line [i, j] for each output line in the output port correspondence queue 58 corresponding to the output port at the port number i.
(J is the output line number) (step F
3), the occupation amount Q of the destination output line A of the packet
_Line [i, A] is compared with threshold value _{Qth (line)} (step F4). If the occupancy Q _line [i, A] is smaller than the threshold value Q _{th (line),} (Q _line [i, A] <Q
_{th (line)} ), the packet reception control unit 56 receives the packet as it is (step F9). On the other hand, if the occupancy Q
_{If line} [i, A] is greater than or equal to threshold value _{Qth (line),} (Q
_line [i, A] ≧ Q _{th (line)} ), packet reception control unit 5
_Reference numeral 6 denotes the number of active VCs VC number N _vc [i,
A] and a predetermined coefficient K, a threshold Q _{th (vc)} is calculated as in the following Expression 3 (step F5).

[0063]

(Equation 3) Here, K is a control parameter that can be freely set by the exchange manager. The packet reception control unit 56 causes the buffer occupancy counting unit 55 to count the occupancy _{Qvc of the} VC belonging to the packet (step F6), and the occupancy _Qvc.
Is compared with the threshold value Q _{th (vc)} (step F7). If the occupancy _Qvc is smaller than the threshold value _{Qth (vc)} ( _Qvc < _{Qth (vc)} ), the packet reception control unit 56 receives the packet as it is (step F9). On the other hand, if the occupation amount Q _vc is equal to or larger than the threshold value Q _{th (vc),} (Q _vc ≧ Q
_{th (vc)} ), the packet reception control unit 56 discards the packet (step F8).

As described above, in the above embodiment, whether or not a packet arriving at the output port corresponding queue 58 in the extended input buffer module unit 50 can be received is determined by the output port corresponding to the output port corresponding to the output port corresponding queue 58. The ratio is calculated in consideration of the ratio of the destination output line corresponding to the packet to the total sum of the acceptable rate calculated by the line corresponding queue 68 multiplied by the number of active VCs for each output line in the output port corresponding queue 58. The threshold is compared with the buffer occupancy of the destination output line. As a result, the buffer occupancy for each output line in the output port corresponding queue 58 is controlled by the rate control unit 58-.
It is possible to make the rate assigned to 2 equal to the ratio of each output line. This has the same effect as controlling the transfer rate according to the output line ratio of the designated transfer rate in the output port corresponding queue 58 in which the output line 93 cannot be distinguished at all.

Further, as a further condition for determining whether or not a packet can be received, a threshold value calculated for a destination output line is used as a threshold value for comparison with the buffer occupancy by the VC to which the packet belongs. Active V
By using the value divided by the number of C, it is possible to achieve fair throughput among a plurality of VCs passing through the same output line.

Next, the extended input buffer module 50
The RM cell processing in the RM cell processing unit 57 in the RM cell processing unit 67 and the RM cell processing unit 67 in the extended output buffer module unit 60 will be described.

When the backward RM cell arrives at the extended input buffer module 50, the backward RM
Since the forward RM cell for the cell should pass through the extended output buffer module unit 60 paired with the extended input buffer module unit 50, the RM cell processing unit 57
Is calculated from the receivable rate calculating unit 66 of the pair of extended output buffer module units 60 and the receivable rate calculated by the global queue 90 addressed to the extended output buffer module unit 60 and the output line corresponding queue 68 through which the forward RM cell passes. The smaller of these values is written to the backward RM cell. When the forward RM cell arrives at the extended input buffer module unit 50, the RM cell processing unit 57
Indicates the forward switch RM length of the virtual switch internal queue length of the virtual switch internal queue 58-3 of the output port corresponding queue 58 of the ABR class in which the forward RM cell is stored.
Write to cell. When the forward RM cell arrives at the extended output buffer module section 60, the RM cell processing section 67 reads the virtual switch internal queue length written in the forward RM cell and restores the global queue length addressed to the output port.

As described above, in the above embodiment, the queue length of the core switch queue 41 (subscripts omitted) and the extended output buffer module in the core switch 40 where congestion occurs because the input rate is higher than the output rate 60
The receivable rate calculation unit 66 calculates the receivable rate from the queue length of the output line corresponding queue 68 in the inside, and notifies the transmitting terminal that generates the ABR class traffic of the
To reflect. This makes it possible to suppress the occurrence of congestion due to ABR class traffic inside the ATM switching system. In addition, the receivable rate calculation unit 66 must grasp the time change of the global queue length in order to calculate the receivable rate in the global queue 90, and each of the extended input buffer module units 50 It is necessary to notify the acceptable rate calculation unit 66 in the extended output buffer module unit 60 of the virtual switch internal queue length of -3. A
In the case of the BR class global queue, the virtual switch internal queue length is written in the forward RM cell passing through each extended input buffer module unit 50, and is read by the extended output buffer module unit 60 to restore the global queue length. By doing so, it is not necessary to prepare extra signal lines and information carrying cells.

Next, a specific case will be described with reference to FIGS. 11 to 28 show the case where N is 2.

In FIGS. 11 to 22, the number of ports / lines is 2/8 and the ATM according to the present invention which can provide four service classes of CBR / VBR / ABR / UBR class.
In the switching system, the core switch unit 40
A first back pressure signal (BP) for stopping the R / VBR / ABR / UBR class. CS) is _80/80 , respectively.
60/40/20 cells, and a second back pressure signal (BP OXB LOW) and a third back pressure signal (BP) OXB The second and for originating the HIGH) 3 threshold Q _{th (bpo xb low)} and _{Q th (bpoxb high)} respectively 8000 cells and 810
0 cells. Note that the second back pressure signal (BP OXB The service class whose transmission can be stopped by LOW) is UBR only.

First, a processing procedure for switching an ATM cell between input / output lines will be described with reference to FIGS. FIGS. 11 to 16 show the first input line 91 (#
1) and the fourth output line 93 (# 4) of the second extended output buffer module section 60-2 between the UBR class V
This shows a state where C is stretched. The first input line 91 (#) of the first extended input buffer module 50-1
UBR set between 1) and the fourth output line 93 (# 4) of the second extended output buffer module unit 60-2.
A description will be given of how input / output line switching is performed for the ATM cell 300 belonging to the class VC1.

FIG. 11 shows that VC1 is an ATM cell # VC1.
Shows the state when the data has arrived at the first extended input buffer module unit 50-1.

First, as shown in FIG. 12, the class / port-specific separator 52 refers to the connection information of the ATM cell 300 and sets the destination output port and the service class type to the second output port 72-2 and the second output port 72-2, respectively. UBR
Class and recognizes the ATM cell 300 as U
It is stored in the virtual source queue 58-1 of the output port correspondence queue 58 addressed to the output port 72-2 for the BR class.

Next, as shown in FIG. 13, the transfer rate value currently set in the rate control unit 58-2 is 10
Since the transmission rate is 0 Mbps, the cell transfer from the virtual source queue 58-1 to the virtual switch internal queue 58-3 takes 100
ATM cell 3 after being controlled to about Mbps.
00 is sent to the virtual switch internal queue 58-3. A
The ATM cells stored before the TM cell 300 are sequentially transmitted from the virtual switch internal queue 58-3, and the ATM cells 300 are transmitted from the virtual switch internal queue 58-.
Reach the beginning of 3.

Here, referring to the back pressure status 301 held by the pack pressure receiving section 54 as shown in FIG.
The first back pressure signal (BP) applied to the UBR class from the core switch queue 41-2 CS)
101 and the second extended output buffer module 60-2
Back pressure signal (BP OXB
LOW) 102 has not been received (“ON” in the back pressure situation 301),
FF "indicates that it has not been received), the rotation priority control unit 59 for the UBR class selects the output port corresponding queue 58 addressed to the second output port 72-2, and the inter-class priority control unit 53 selects the UBR class. When the class is selected, the ATM cell 300 is taken out from the virtual switch internal queue 58-3 and corresponds to the second output port 72-2 via the first input port 71-1 and the time division multiplex bus 42. And stored in the second core switch queue 41-2.
The ATM cells stored before the cell 300 are sequentially transmitted from the second core switch queue 41-2, starting from the ATM cell stored therein.
When the ATM cell 300 is in the second core switch queue 41-2.
Reaches the beginning.

Here, as shown in FIG. 15, referring to the back pressure receiving status 302 held by the back pressure receiving unit 45, the second extended output buffer module unit 60-2 of the second output port 72-2 is referred to. From the third back pressure signal (BP OXB HIG
H), the ATM cell 300 receives the second output port 72- from the second core switch queue 41-2.
2 to the subsequent second extended output buffer module 60-2. In the second extended output buffer module unit 60-2, the class / line-specific separator 62 refers to the connection information of the ATM cell 300 and sets the destination output line and the service class type to the fourth output line 93 (# 4) Recognizing that the cell is of the UBR class, the ATM cell 300 is stored in the output line correspondence queue 68 addressed to the fourth output line 93 (# 4) for the UBR class.
The ATM cells stored before the ATM cell 300 are sequentially transmitted from the output line corresponding queue 68 in order from the ATM cell stored therein.
The M cell 300 reaches the head of the output line corresponding queue 68.

Here, as shown in FIG. 16, the inter-class priority control unit 63 for the fourth output line 93 (# 4)
When the class is selected, the first cell is set to the fourth output line 9
3 (# 4).

Next, referring to FIGS. 17 and 18, the core switch queue length is set to the first pack pressure signal (BP). A processing procedure when a plurality of ATM cells arrive at the same time when the threshold value is equal to or less than the CS) generation threshold will be described. FIG. 17 shows the second output port 72-2 for the second output port 72-2.
The first of back pressure signal core switch queue length Q _cs of the core switch queue 41-2 for the UBR class stop of (BP CS) 101 is less than or equal to the first threshold value Q _{th (bpcs)} (= 20 cells), and the plurality of ATM cells 300 are connected to the second output port 72-2 for the second output port 72-2.
2 shows a state when the data arrives at the core switch queue 41-2 at the same time. This By storing the ATM cell 300, core switches queue length Q _cs of the second core switch queue 41-2 exceeds the first threshold _{Q th (bpcs).} Therefore, as shown in FIG. 18, the back pressure transmitting unit 44 transmits a first back pressure signal (BP) for stopping transmission of the UBR class cell destined for this port. CS) 101 to all extended input buffer module units 50-1 and 50-2. In each of the extended input buffer module sections 50-1 and 50-2, the back pressure receiving section 54 receives the first back pressure signal (BP). CS) 101,
The transmission of the UBR raster cell to the second output port 72-2 is stopped.

Similarly, the core switch queue length Q_csIs
Threshold Q for service class_{th (bpcs)}Over
The service class for the core switch queue.
Back pressure for stopping cell transmission of cells
-Signal (BP CS) 101 for all extended input buffers
Send to module units 50-1 and 50-2
You. In this embodiment, individual service classes are applied individually.
Back pressure signal (BP CS) was prepared
Is the first back pressure signal (BP) CS)
Can be configured to apply to multiple service classes.
Both are possible.

Referring to FIGS. 19 and 20, extended output
When the buffer occupancy of the buffer module unit 60 is
Pressure signal (BP OXB LOW) For generation
When the ATM cell arrives
The processing procedure will be described. FIG. 19 shows the second extended output bar.
Buffer occupancy Q of the buffer module 60-2_obxBut
When the number of cells is 7999, the ATM cell 300 is
When it arrives at the output buffer module 60-2.
The state is shown. This ATM cell 300 can be stored.
And the buffer occupancy Q_obxIs the second back pressure
-Signal (BP OXB LOW) 102 for sending
Second threshold Q_{th (bpoxb low)}(= 8000 cells)
It will be on top. Therefore, as shown in FIG.
In the extended output buffer module unit 60-2,
The pressure transmitter 64 is configured to transmit the second back pressure signal.
No. (BP OXB LOW) 102 to all extended input
Issued to the buffer module sections 50-1 and 50-2.
I believe. Each extended input buffer module 50-1 and
50-2, the back pressure receiving unit 54
The second back pressure signal (BP OXB LO
W) Upon receiving 102, the second output port 72-2 line
Transmission of the UBR class cell is stopped.

In this embodiment, the second back pressure signal (BP OXB Although the service class to which the (LOW) 102 is applied is limited to the UBR class, it may be configured to be applied to a plurality of service classes.

Referring to FIGS. 21 and 22, extended output
The buffer occupancy of the buffer module unit 60 is
Pressure signal (BP OXB HIGH) occurrence
The ATM cell arrives when it is below the threshold
Will be described. FIG. 21 shows the second extension battery.
Buffer occupancy Q of the fa module section 60-2_obxIs 8
099 cell, the ATM cell 300 has the second extension
The state when it arrives at the output buffer module unit 60-2
State. Storing this ATM cell 300
Then, the third back pressure signal (BP OXB H
IGH) Third threshold Q for transmitting 103
_{th (bpoxb high)}(= 8100) or more. So
Here, as shown in FIG.
In the rule unit 60-2, the back pressure transmitting unit 64
Third back pressure signal (BP OXB HIG
H) Send 103 to the immediately preceding core switch unit 40
You. The core switch unit 40 receives back pressure
The unit 45 receives the third back pressure signal (BP O
XB HIGH) 103, the second core switch
Stop all cell transmission to the switch queue 41-2.
You.

FIGS. 23 to 26 show an ATM according to the present invention.
In the switching system, the first input line 91 (# 1) of the first extended input buffer module unit 50-1 and the second
And the fourth output line 93 (# 4) of the extended output buffer module unit 60-2. The input line paired with the fourth output line 93 (# 4) of the second extended output buffer module unit 60-2 is the fourth input line 91 (#) of the second extended input buffer module unit 50-2. 4)
The backward RM cell of C2 arrives at the fourth input line 91 (# 4) of the second extended input buffer module 50-2. Then, it flows to the first output line 93 (# 1) of the first extended output buffer module unit 60-1.

Referring to FIGS. 23 and 24, the forward RM cell carries the queue length corresponding to the output port in extended input buffer module unit 50, and buffer occupancy counting unit 65 in extended output buffer module unit 60 A processing procedure for recognizing the global queue length will be described. As shown in FIG. 23, the first input line 91 (# 1) of the first extended input buffer module unit 50-1 and the fourth output line 9 of the second extended output buffer module unit 60-2.
3 (# 4), when the forward RM cell 303 belonging to the VC2 of the ABR class arrives at the first extended input buffer module unit 50-1, the class / port-specific separator 52 sets the forward RM Referring to the connection information of the cell 303, the destination output port and the service class type are respectively set to the second output port 72-2, AB
Recognizing that it is the R class, the forward RM cell 303 is transferred to the virtual source queue 58-of the output port corresponding queue 58 addressed to the second output port 72-2 for the ABR class.
1 is stored. At the same time, the RM cell processing unit 57 writes the virtual switch internal queue length of the virtual switch internal queue 58-3 of the ABR class queue in which the forward RM cell 303 is stored in the forward RM cell 303. At this time, since the queue length inside the virtual switch of the stored ABR class queue is 40 cells, 40 cells are described in the forward RM cell 303.

FIG. 24 shows a forward RM cell 30 of VC2.
3 shows a state when the third data has arrived at the second extended output buffer module unit 60-2. The class / line-specific separator 62 refers to the connection information of the forward RM cell 303 and recognizes that the destination output line and the service class type are the fourth output line 93 (# 4) and the ABR class, respectively. AB the forward RM cell 303
It is stored in the output line correspondence queue 63 addressed to the fourth output line 93 (# 4) for the R class. At the same time, the RM cell processing unit 67 transmits the A in the first extended input buffer module unit 50-1 described in the forward RM cell.
The BR-class output port-corresponding queue length is extracted and notified to the buffer occupancy counter 65. In the buffer occupancy counting unit 65 of the second extended output buffer module 60-2, in order to recognize the global queue length for each service class, the buffer occupancy counter 65 corresponding to the same output port existing in each extended input buffer module unit 50 The queue length is stored for each service class, and according to the notification from the RM cell processing unit 67, the A of the first extended input buffer module 50-1 through which the forward RM cell 303 has passed is stored.
Output port queue length for BR class forward R
Replace with the contents of M cell 303.

In this embodiment, the buffer occupancy counter 65 of the second extended output buffer module 60-2 is first addressed to the second output port 72-2 of the first extended input buffer module 50-1. ABR class queue is 1
0, but the forward RM cell 30 from the first extended input buffer module unit 50-1.
With the arrival of 3, this has been changed to 40 cells. Originally, a special information carrying cell used only inside the ATM switching system is prepared to inform the buffer occupancy counter 65 of the extended output buffer module 60 of the queue length corresponding to the output port of the extended input buffer module 50. However, by using the forward RM cell only for the ABR class, there is no need to prepare extra information-carrying cells or signal lines, and the amount of hardware implemented can be reduced accordingly. It is possible. In addition, there is an effect that the frequency of occurrence of internal congestion caused by the information carrying cell for controlling the ATM switching system which is not the user's data cell is reduced.

Next, with reference to FIGS. 25 and 26, the acceptable rate for the ABR class calculated by the global queue and the output line corresponding queue 68 in the extended output buffer module unit 60 is described in the backward RM cell. The processing procedure will be described. As shown in FIG. 25, when the backward RM cell 304 of VC2 arrives at the fourth input line 91 (# 4) of the second extended input buffer module unit 50-2, the class / port-specific separator 52 receives the destination. The RM cell processing unit 5 recognizes the output port and the service class type and stores them in the corresponding virtual source queue 58-1.
7 is a global queue 90 corresponding to the second output port 72-2 through which the VC2 passes, and a fourth output line 93 (# 4) of the second extended output buffer module unit 60-2.
Is referenced in the output line corresponding queue 68 corresponding to.

As shown in FIG. 26, the second output port 7
The receivable rate in the global queue corresponding to 2-2 is 40 Mbps, while the receivable rate in the output line corresponding queue 68 corresponding to the fourth output line 93 (# 4) of the second extended output buffer module unit 60-2. Since the rate is 20 Mbps, the data is written into the backward RM cell 304 of 20 Mbps which is the smaller value.

Referring to FIG. 27, a description will be given of a processing procedure for setting an acceptable rate in rate control section 58-2 in extended input buffer module section 50. FIG. 27 shows the first
Shows that the transfer rate R [2] is set in the rate control unit 58-2 of the output port correspondence queue 58 of a certain service class corresponding to the second output port 72-2 of the extended input buffer module unit 50-1 of FIG. ing. The receivable rate calculating unit 66 periodically calculates the receivable rate in each queue, but every time the calculation is executed, the rate control unit 58-2.
Set the rate to. By the latest rate calculation processing, the receivable rate ER _g [2｝] in the global queue of the second output port 72-2 is 80 Mbps, and the first to the second stored in the second extended output buffer module unit 60-2. 4 output line 93 (# 1, # 2, # 3, # 4)
The acceptable rate ER _line [2, j] (j = 1, 2, 3, 4) in the output line corresponding queue is 5 Mbps, 10 Mbps, 15 Mbps, and 20 Mbps, respectively.
s. At this time, the total number of active VCs N _vc [2] in the output port corresponding queue 58 corresponding to the second output port 72-2 of the first extended input buffer module unit 50-1 is 4, and the second extended output The first to fourth output lines 93 of the buffer module unit 60-2 (# 1, # 2,
# 3, # 4) Total number of active VCs N _vc [2, j]
(J = 1, 2, 3, 4) are 2, 1, 0, 1 respectively, and the transfer rate R set in the output port corresponding queue 58
[2] is represented by Equation 4 below.

[0090]

(Equation 4) Output port corresponding queue 5 corresponding to second output port 72-2 of first extended input buffer module unit 50-1
8 is set to 40 Mbps in the rate control unit 58-2.
This rate setting process is performed for each service class using the acceptable rate for that service class.

Next, with reference to FIG. 28, a description will be given of a processing procedure for determining whether or not a packet can be received when the head cell of the packet arrives at the extended input buffer module unit 50. FIG. 28 shows the first input line 91 (# 1) of the first extended input buffer module section 50-1 and the fourth input line 91 (# 1) of the second extended output buffer module section 60-2 in the ATM switching system according to the present invention. A UBR class VC7 is set up between the output line 93 (# 4) and the
7 shows the state when the head cell of the packet belonging to 7 has arrived. The fixed threshold Q _th set to the queue is 5
00 cells.

In FIG. 28, the output line corresponding to the first to fourth output lines 93 (# 1, # 2, # 3, # 4) accommodated in the second extended buffer module section 60-2. Acceptable rate ER in queue 68
_line [2, j] are 5Mbps, 10Mbps,
They are 15 Mbps and 20 Mbps. The second output port 72- of the first extended input buffer module unit 50-1
2 in the output port correspondence queue 58 corresponding to
, The total number of active VCs _Nvc [2, j] (j = 1, 2) addressed to the first to fourth output lines 93 (# 1, # 2, # 3, # 4) of the extended output buffer module unit 60-2 of FIG. 2,3,4)
Are 2, 1, 0, and 1, respectively, and the threshold value Q _{th (line)} to be compared with the buffer occupancy for each output line is represented by the following Expression 5.

[0093]

(Equation 5) At this point, the first extended input buffer module 50
The buffer occupancy by the destination output line of VC7 (the fourth output line 93 (# 4)) in the output port correspondence queue 58 corresponding to the second output port 72-2 of -1 is 300.
Since the cell exceeds the threshold value Q _{th (line)} , VC
The threshold value Q _{th (vc)} to be compared with the occupation amount for each is represented by the following equation (6 _).
Calculate according to

[0094]

(Equation 6) Here, 1.0 is used as the value of the control parameter K, which is a value that can be freely set by the exchange manager.
Since the buffer occupation amount by the VC 7 exceeds the threshold value Q _{th (vc)} in 300 cells, it is determined that the packet whose head is this cell is discarded, and the packet reception control unit 56 determines that this head cell and this packet are discarded. Control is performed so that all cells of the VC 7 arriving before the last cell arrives are discarded. Here, if either the buffer occupancy by the destination output line or the buffer occupancy by the VC 7 is smaller than the threshold value, it is determined that the packet whose head is this cell is received.

The embodiments described in detail in the present specification and the drawings do not limit the present invention. Various modifications within the spirit and scope of the invention are within the scope of the invention.

[0096]

The present invention has the following effects. In order to realize an ATM switching system having a large switching capacity, a conventional system in which a low-speed line interface is directly accommodated in a time-division multiplexed bus and a switch configuration of the present invention in which a higher-speed port interface is directly accommodated, Obviously, the switch configuration according to the present invention has a smaller number of interfaces accommodated in the time division multiplex bus, and
It is possible to suppress the occurrence of problems such as a shortage of pins on the I-mount. In addition, an output port corresponding queue in the extended input buffer module is prepared for each service class, and the application of the back pressure signal transmitted from the core switch and the extended output buffer module is subdivided for each service class to prevent cell loss. Accordingly, it is possible to easily provide various service class qualities with respect to the cell loss rate and the delay.

Further, according to the present invention, the utilization rate is increased without causing congestion in the global queue where the input rate is higher than the output rate and where congestion occurs, or in the output line corresponding queue in the extended output buffer module unit. The cell transfer rate from the virtual source queue to the virtual switch internal queue is calculated by calculating the acceptable reception rate and the output port corresponding queue in the extended input buffer module as a dual configuration of the virtual source queue and the virtual switch internal queue. Is controlled based on the receivable rate calculated by the downstream module of the ATM switching system, so that for indistinct input traffic that does not specify traffic characteristics, which is a major factor causing internal congestion of the ATM switching system, Temporarily store them in a virtual source queue To limit substantial inflow into the internal ATM exchange Te it is possible to suppress the occurrence frequency of the internal congestion, it is possible to eliminate the interference between service classes according to internal congestion.

Further, it is possible to control cell transfer to the entire output port, but not to control for each output line accommodated by the output port. All of the extended input buffers set the sum of the acceptable rate calculated in the output line corresponding queue accommodated by the output port and the number of active VCs for each output line in the output port corresponding queue in the rate control unit. By using the module unit, even if the number of VCs to the same output line varies among the extended input buffer module units, each extended input buffer module unit autonomously adjusts the transmission rate in consideration of the number of VCs per output line. Since the determination is made, it is possible to guarantee an even throughput between VCs going to the same output line.

Whether or not a packet arriving at the output port corresponding queue in the extended input buffer module unit can be received is determined based on the acceptable rate calculated by the output line corresponding queue accommodated by the corresponding output port of the output port corresponding queue. Active V for each output line in the corresponding queue
By comparing a threshold calculated in consideration of a ratio of a packet occupied by a portion corresponding to the destination output line to the sum of the products multiplied by the number of Cs and the buffer occupancy by the destination output line, the output port-corresponding queue is determined. It is possible to make the buffer occupancy of each output line the same as the ratio of the rate assigned to the rate control unit to each output line, and in the output port corresponding queue where output lines cannot be distinguished at all, this is the specified transfer rate If the transfer rate is controlled in accordance with the output line ratio, the same effect is obtained.

Further, as a further condition for determining whether or not a packet can be received, a threshold value to be compared with the buffer occupancy of the VC to which the packet belongs is determined by a threshold value calculated for the destination output line. Dividing by the number of active VCs makes it possible to achieve fair throughput among a plurality of VCs passing through the same output line.

The transmitting terminal which calculates the acceptable rate in the core switch queue in which congestion occurs because the input rate is higher than the output rate and the output line corresponding queue in the extended output buffer module unit and generates the ABR class traffic is calculated. , It is possible to suppress the occurrence of congestion due to ABR class traffic inside the ATM switching system. In addition, the receivable rate calculation unit must grasp the time change of the global queue length in order to calculate the receivable rate in the global queue. It is necessary to notify the acceptable calculation section in the module section.
As for the global queue of the ABR class, the internal queue length of the virtual switch is written in the forward RM cell passing through each extended input buffer module section, and is read by the extended output buffer module side to restore the global queue length. By doing so, there is no need to prepare extra signal lines and information carrying cells.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an ATM switching system according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of an extended input buffer module used in the ATM switching system shown in FIG.

FIG. 3 is a block diagram showing a configuration of a core switch unit used in the ATM switching system shown in FIG. 1;

FIG. 4 is a block diagram showing a configuration of an extended output buffer module used in the ATM exchange system shown in FIG. 1;

FIG. 5 is a diagram showing a configuration of a buffer occupancy information table stored in a buffer occupancy counter of an extended input buffer module of the ATM switching system shown in FIG. 1;

FIG. 6 is a diagram showing a configuration of a buffer occupancy information table stored in a buffer occupancy counter of a core switch unit of the ATM switching system shown in FIG. 1;

FIG. 7 is a diagram showing a configuration of a buffer occupancy information table stored in a buffer occupancy counter of an extended output buffer module of the ATM switching system shown in FIG. 1;

FIG. 8 is a diagram showing a back pressure control in the ATM switching system shown in FIG. 1;

FIG. 9 is a diagram of an acceptable rate calculation environment in the ATM exchange system shown in FIG. 1;

FIG. 10 is a flowchart of a process of selecting and discarding a packet in the ATM switching system shown in FIG. 1;

11 is a state diagram illustrating an initial (first) stage of a processing procedure when switching ATM cells between input and output lines in the ATM switching system illustrated in FIG. 1;

FIG. 12 is a state diagram illustrating a second stage of the processing procedure.

FIG. 13 is a state diagram illustrating a third stage of the processing procedure.

FIG. 14 is a state diagram illustrating a fourth stage of the processing procedure.

FIG. 15 is a state diagram illustrating a fifth stage of the processing procedure.

FIG. 16 is a state diagram illustrating a sixth (last) stage of the processing procedure.

17 is a first half of a processing procedure when a plurality of ATM cells arrive at the same time when the core switch queue length is equal to or less than the first pack pressure signal generation threshold in the ATM exchange system shown in FIG. FIG. 4 is a state diagram for explaining FIG.

FIG. 18 is a state diagram for explaining the latter half of the processing procedure.

FIG. 19 shows a processing procedure when an ATM cell arrives when the buffer occupancy of the extended output buffer module section is equal to or less than a second back pressure signal generation threshold value in the ATM switching system shown in FIG. It is a figure for explaining the first half.

FIG. 20 is a diagram illustrating the latter half of the processing procedure.

FIG. 21 shows a processing procedure when an ATM cell arrives when the buffer occupancy of the extended output buffer module is equal to or smaller than a third back pressure signal generation threshold in the ATM switching system shown in FIG. It is a figure for explaining the first half.

FIG. 22 is a diagram for explaining the latter half of the processing procedure.

23. In the ATM switching system shown in FIG. 1, the forward RM cell carries the queue length corresponding to the output port in the extended input buffer module unit, and the buffer occupancy counting unit in the extended output buffer module unit determines the global queue length. It is a figure for explaining the first half of the processing procedure to recognize.

FIG. 24 is a diagram for explaining the latter half of the processing procedure.

FIG. 25 is a first half of a processing procedure for describing an acceptable rate for an ABR class calculated in a global queue and an output line corresponding queue in an extended output buffer module unit in a backward RM cell in the ATM exchange system shown in FIG. 1; FIG.

FIG. 26 is a diagram illustrating the latter half of the processing procedure.

FIG. 27 is a state diagram for explaining a processing procedure for setting an acceptable rate in a rate control unit in the extended input buffer module unit in the ATM switching system shown in FIG. 1;

FIG. 28 is a state diagram illustrating a processing procedure for determining whether or not to receive a packet when the head cell of the packet arrives at the extended input buffer module in the ATM switching system shown in FIG. 1;

FIG. 29 is a block diagram showing a configuration of a first conventional ATM switching system.

FIG. 30 is a block diagram showing a configuration of an input buffer module used in the ATM switching system shown in FIG. 29;

FIG. 31 is a block diagram showing a configuration of a core switch unit used in the ATM switching system shown in FIG. 29;

FIG. 32 is a block diagram showing a configuration of a second conventional ATM switching system.

FIG. 33 is a block diagram showing a configuration of an extended input buffer module used in the ATM switching system shown in FIG. 32;

FIG. 34 is a block diagram showing a configuration of a core switch unit used in the ATM switching system shown in FIG. 32;

FIG. 35 is a block diagram showing a configuration of an extended output buffer module used in the ATM switching system shown in FIG. 32;

[Explanation of symbols]

 40 core switch unit 50-1 to 50-N extended input buffer module unit 60-1 to 60-N extended output buffer module unit 71-1 to 71-N input port 72-1 to 72-N output port 91 input line 93 Output line 101-103 Back pressure signal

Claims (24)

[Claims] An ATM switching system for exchanging ATM cells between a plurality of low-speed input lines and a plurality of low-speed output lines, having an ATM switching function between a high-speed input port and a high-speed output port. A core switch unit of an output buffer type configuration, at least one extended input buffer module unit for multiplexing ATM cells from the plurality of low-speed input lines to the high-speed input port, and an output from the high-speed output port. At least one extended output buffer module for separating into a plurality of low-speed output lines, wherein the extended input buffer module enables queuing of ATM cells for each destination output port and for each service class; ATM exchange that enables queuing in the buffer module unit for each destination output line and for each service class The core switch unit, when the queue length of a core switch queue prepared for each output port exceeds a first threshold, sends a first back pressure signal to all of the extended input buffer module units. The extended output buffer module section generates a second back pressure signal to all of the extended input buffer module sections when the total buffer occupancy exceeds a second threshold value. Means for stopping cell output to an output port transmitting the first back pressure signal in response to the first back pressure signal, and responsive to the second back pressure signal. Means for stopping cell output to an output port for transmitting the signal.
TM exchange system. 2. An ATM switching system for exchanging ATM cells between a plurality of low-speed input lines and a plurality of low-speed output lines, having an ATM switching function between a high-speed input port and a high-speed output port. A core switch unit of an output buffer type configuration, at least one extended input buffer module unit for multiplexing ATM cells from the plurality of low-speed input lines to the high-speed input port, and an output from the high-speed output port. At least one extended output buffer module for separating into a plurality of low-speed output lines, wherein the extended input buffer module enables queuing of ATM cells for each destination output port and for each service class; ATM exchange that enables queuing in the buffer module unit for each destination output line and for each service class In the system, the core switch unit sends a first back pressure signal to all the extended input buffer module units when a queue length of a core switch queue prepared for each output port exceeds a first threshold value. The extended output buffer module includes a means for generating a second back pressure signal to the core switch when the total buffer occupancy exceeds a second threshold, The extended input buffer module unit includes means for stopping cell output to an output port transmitting the first back pressure signal in response to the first back pressure signal, wherein the core switch unit responds to the second back pressure signal. And means for stopping cell output to the extended output buffer module for transmitting the signal. M switch system. 3. An ATM switching system for exchanging ATM cells between a plurality of low-speed input lines and a plurality of low-speed output lines, having an ATM switching function between a high-speed input port and a high-speed output port. A core switch unit of an output buffer type configuration, at least one extended input buffer module unit for multiplexing ATM cells from the plurality of low-speed input lines to the high-speed input port, and an output from the high-speed output port. At least one extended output buffer module for separating into a plurality of low-speed output lines, wherein the extended input buffer module enables queuing of ATM cells for each destination output port and for each service class; ATM exchange that enables queuing in the buffer module unit for each destination output line and for each service class The core switch unit, when the queue length of a core switch queue prepared for each output port exceeds a first threshold, sends a first back pressure signal to all of the extended input buffer module units. The extended output buffer module section generates a second back pressure signal to all the extended input buffer module sections when the total buffer occupancy exceeds a second threshold value. Means for generating a third back pressure signal to the core switch unit when the total buffer occupancy exceeds a third threshold value, wherein the extended input buffer module unit comprises: Means for halting cell output to an output port transmitting said back pressure signal in response to said second back pressure signal; Means for stopping cell output to an output port transmitting the signal in response to a signal, wherein the core switch unit transmits the signal in response to a third back pressure signal. An ATM switching system including means for stopping cell output to the ATM switch. 4. The extended output buffer module section,
A first one of virtual queues (global queues) composed of a set of queues addressed to the same output among output port corresponding queues existing in all of the extended input buffer module units.
And a rate calculating means for periodically calculating a second acceptable rate in an output line corresponding queue existing in the extended output buffer module unit. The ATM exchange system according to any one of claims 1 to 4. 5. An extended input buffer module unit having means for periodically transmitting a special switch internal control cell describing an output port corresponding queue length, wherein each extended output buffer module unit 5. The apparatus according to claim 4, further comprising means for restoring the global queue length based on the contents of the switch internal control cell, whereby the rate calculating means can grasp the global queue length. ATM exchange system. 6. An available bit rate service (AB) capable of adaptively changing a transmission rate according to a degree of network congestion as one of the service classes.
R) class, and for the ABR class, when a forward RM cell sent in the direction from the transmitting terminal to the receiving terminal passes through the extended input buffer module unit,
The output queue corresponding to the BR class is described, and when the extended output buffer module receives the forward RM cell, the entire global queue of the ABR class is calculated from the output port corresponding queue described in the forward RM cell. The ATM switching system according to claim 5, wherein the queue length is restored. 7. An available bit rate service (AB) capable of adaptively changing a transmission rate according to a degree of network congestion as one of the service classes.
R) class, wherein the extended output buffer module unit calculates a receivable rate on a regular basis from a state time change of the global queue for the ABR class or the output line corresponding queue of the extended output buffer module unit. The extended input buffer module unit, for the logical channel (VC) of the ABR class, assigns the smaller of the global queue through which the ABR class passes and the acceptable rate presented by the output line corresponding queue to the smaller value. Logical channel (V
The ATM exchange system according to any one of claims 1 to 3, further comprising: means for describing in a backward RM cell transmitted from the accepting terminal to the transmitting terminal in (C). 8. The extended output buffer module section,
It has means for periodically calculating an acceptable rate for each service class from a change in the state time of the global queue or the output line corresponding queue for each service class, and the extended input buffer module unit is configured to calculate each acceptable rate based on the acceptable rate. 2. An internal rate control means for controlling cell output to an output port.
4. The ATM switching system according to any one of claims 1 to 3. 9. The output port corresponding queue installed in the extended input buffer module unit includes a virtual source queue, a virtual switch internal queue, and a rate provided between the virtual sole queue and the virtual switch internal queue. And a control unit, wherein the rate control unit controls cell transfer from the virtual source queue based on an acceptable rate calculated in a global queue or an output line corresponding queue. 1 to 3
The ATM exchange system according to any one of claims 1 to 4. 10. A transfer rate set in the rate control unit, an acceptable rate calculated in a global queue addressed to an output port corresponding to the output port corresponding queue, and a cell currently stored in the output port corresponding queue. Is the product of the number of logical channels (the number of active logical channels) stored therein, or the acceptable rate for each output line calculated by each output line corresponding queue accommodated by the output port corresponding to the output port corresponding queue. 10. The ATM switching system according to claim 9, wherein a smaller one of a sum of respective products of the number of active logical channels for each output line in said output port corresponding queue is used. 11. The extended input buffer module section monitors the buffer occupancy of an output port corresponding queue in each output line and each logical channel (VC), and determines the first cell of the packet as the output cell. When the packet arrives at the port corresponding queue, when the buffer occupancy by the destination output line of the packet in the output port corresponding queue and the buffer occupancy by the logical channel (VC) exceed the respective thresholds, The ATM switching system according to any one of claims 1 to 3, further comprising means for discarding the ATM. 12. A threshold value, which is calculated for each output line corresponding queue in the extended output buffer module of the destination output port of the packet, as a threshold value to be compared with the buffer occupancy of the packet by the destination output line in the output port corresponding queue. Of the total number of active logical channels per output line in the output port corresponding queue and the acceptable rate, the ratio of the destination output line equivalent of the packet to the fixed threshold value set for the entire output port corresponding queue. The value calculated above is used as a value to be compared with the buffer occupancy of the packet in the output port corresponding queue by the logical channel (VC) in the output port corresponding queue. Using the value divided by the number of active logical channels of the ATM exchange system according to claim 11. 13. A traffic control method in an ATM switching system for exchanging ATM cells between a plurality of low-speed input lines and a plurality of low-speed output lines, wherein the ATM switching system has a high-speed input port and a high-speed output port. A core switch unit having an output buffer type configuration having an ATM switching function between the core switch unit and at least one extended input buffer module unit for multiplexing ATM cells from the plurality of low-speed input lines to the high-speed input port; At least one extended output buffer module for separating an output from a high-speed output port into the plurality of low-speed output lines;
The extended input buffer module unit enables queuing of ATM cells for each destination output port and for each service class, and the extended output buffer module unit enables queuing for each destination output line and for each service class. In the traffic control method for an exchange system, in the core switch unit, when a queue length of a core switch queue prepared for each output port exceeds a first threshold value, a first back pressure signal is extended to all of the expansions. When the first back pressure signal is received by the extended input buffer module, the cell output to the output port transmitting the first back pressure signal is stopped at the extended input buffer module. When the total buffer occupancy exceeds a second threshold, A back pressure signal is generated to all of the extended input buffer module sections. When the extended input buffer module section receives the second back pressure signal, it stops cell output to an output port transmitting the second back pressure signal. A traffic control method for an ATM switching system, comprising the steps of: 14. A traffic control method in an ATM switching system for exchanging ATM cells between a plurality of low-speed input lines and a plurality of low-speed output lines, said ATM switching system comprising a high-speed input port and a high-speed output port. A core switch unit of an output buffer type configuration having an ATM switching function with a port, and an ATM from the plurality of low-speed input lines
An extended input buffer module for multiplexing cells to the high-speed input port; and an extended output buffer module for separating an output from the high-speed output port to the plurality of low-speed output lines. The unit enables queuing of ATM cells for each destination output port and for each service class, and the extended output buffer module unit enables queuing for each destination output line and for each service class. In the method, when a queue length of a core switch queue prepared for each output port exceeds a first threshold value, a first back pressure signal is sent to all the extended input buffer module units. Generating the first backup data in the extended input buffer module unit. When receiving a shear signal, the cell output to the output port transmitting the signal is stopped, and when the total buffer occupancy exceeds a second threshold in the extended output buffer module section, the second Generating a back pressure signal to the core switch unit; and stopping the cell output to the extended output buffer module unit that transmits the second back pressure signal when the core switch unit receives the second back pressure signal. A traffic control method for an ATM exchange system. 15. A traffic control method in an ATM switching system for exchanging ATM cells between a plurality of low-speed input lines and a plurality of low-speed output lines, wherein the ATM switching system has a high-speed input port and a high-speed output. A core switch unit of an output buffer type configuration having an ATM switching function with a port, and an ATM from the plurality of low-speed input lines
At least one extended input buffer module for multiplexing cells to the high-speed input port; and at least one extended output buffer module for separating the output from the high-speed output port to the plurality of low-speed output lines. The extended input buffer module enables queuing of ATM cells for each destination output port and for each service class, and the extended output buffer module enables queuing for each destination output line and for each service class. In the traffic control method for an ATM switching system, when the queue length of a core switch queue prepared for each output port exceeds a first threshold value in the core switch unit, the first back pressure signal is transmitted to all of the core switch queues. The extended input buffer generated in the extended input buffer module section; When the first back pressure signal is received by the module, the cell output to the output port transmitting the first back pressure signal is stopped, and the total buffer occupancy of the extended output buffer module is reduced by the second threshold. When the value exceeds the value, a second back pressure signal is generated to all the extended input buffer module units, and when the second back pressure signal is received by the extended input buffer module unit, the second back pressure signal is transmitted. Stopping the cell output to an output port, and generating a third back pressure signal to the core switch unit when the total buffer occupancy exceeds a third threshold value in the extended output buffer module unit; The extended output buffer module for transmitting the third back pressure signal when the core switch unit receives the third back pressure signal. Traffic control method in the ATM switching system, characterized in that it comprises a step of stopping the cell output to parts. 16. A first reception in a virtual queue (global queue) composed of a set of queues destined for the same output among output port corresponding queues present in all of the extended input buffer module units in the extended output buffer module unit. The method according to any one of claims 13 to 15, further comprising a step of periodically calculating a possible rate and a second acceptable rate in an output line corresponding queue existing in the extended output buffer module unit. 5. A traffic control method for an ATM switching system according to any one of the first to fifth aspects. 17. In each extended input buffer module unit,
A step of periodically transmitting a special switch internal control cell describing an output port corresponding queue length, and restoring a global queue length in each extended output buffer module unit based on the contents of the switch internal control cell that arrives; 17. The traffic control method for an ATM switching system according to claim 16, further comprising: 18. An available bit rate service (AB) capable of adaptively changing a transmission rate according to a degree of network congestion as one of the service classes.
R) class, and describes, for the ABR class, a queue length corresponding to an output port of the ABR class when a forward RM cell sent in the direction from the transmitting terminal to the receiving terminal passes through the extended input buffer module unit. And the extended output buffer module unit is configured to
18. The method of claim 17, further comprising: when receiving an M cell, restoring the total queue length of an ABR class global queue from the output port corresponding queue length described in the forward RM cell. A traffic control method for an ATM switching system. 19. An available bit rate service (AB) capable of adaptively changing a transmission rate according to a degree of network congestion as one of the service classes.
R) class, wherein the extended output buffer module unit periodically calculates an acceptable rate from a state time change of the global queue for the ABR class or the output line corresponding queue of the extended output buffer module unit, In the extended input buffer module unit, for the logical channel (VC) of the ABR class, the smaller value of the global queue through which the ABR class passes and the acceptable rate presented by the output line corresponding queue is assigned to the logical channel (V
The traffic of the ATM switching system according to any one of claims 1 to 3, further comprising a step of describing in a backward RM cell transmitted from the accepting terminal to the transmitting terminal in the step (C). Control method. 20. The extended output buffer module unit periodically calculates an acceptable rate for each service class from a change in the state time of a global queue or an output line corresponding queue for each service class. 16. The traffic control method for an ATM switching system according to claim 11, further comprising a step of controlling cell output to each output port based on the acceptable rate. 21. A queue corresponding to an output port provided in the extended input buffer module section has a dual configuration of a virtual source queue and a virtual switch internal queue, and cell transfer from the virtual source queue is performed by a global queue or an output line. 14. The method according to claim 13, further comprising a step of controlling a rate control unit provided between the virtual sole queue and the virtual switch internal queue based on an acceptable rate calculated in the corresponding queue. 15. The traffic control method for an ATM switching system according to any one of 15. 22. As the transfer rate set in the rate control unit, an acceptable rate calculated in a global queue addressed to an output port corresponding to the output port corresponding queue, and a cell currently stored in the output port corresponding queue. Is the product of the number of logical channels (the number of active logical channels) stored therein, or the acceptable rate for each output line calculated by each output line corresponding queue accommodated by the output port corresponding to the output port corresponding queue. 22. The traffic control method for an ATM switching system according to claim 21, wherein a smaller one of sums of respective products of the number of active logical channels for each output line in said output port corresponding queue is used. 23. The extended input buffer module section monitors the buffer occupancy of an output port corresponding queue in each output line and each logical channel (VC), and determines the head cell of the packet as the output cell. When the packet arrives at the port corresponding queue, when the buffer occupancy by the destination output line of the packet in the output port corresponding queue and the buffer occupancy by the logical channel (VC) exceed the respective thresholds, 16. The traffic control method for an ATM switching system according to claim 13, further comprising the step of: 24. A threshold value calculated for each output line corresponding queue in the extended output buffer module unit of the destination output port of the packet as a threshold value to be compared with the buffer occupancy of the packet in the output port corresponding queue by the destination output line. Of the total number of active logical channels per output line in the output port corresponding queue and the acceptable rate, the ratio of the destination output line equivalent of the packet to the fixed threshold value set for the entire output port corresponding queue. The value calculated above is used as a value to be compared with the buffer occupancy of the packet in the output port corresponding queue by the logical channel (VC) in the output port corresponding queue. Using the value divided by the number of active logical channels of the Traffic control method in the ATM exchange system according to claim 23.