JP3047891B2 - ATM switch - Google Patents

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) switch, in particular, includes a cell buffer (buffer memory) on the input side and a cell buffer on the output side, and the back pressure is controlled by the back pressure signal from the cell buffer on the output side. It relates to a type ATM switch.

[0002]

2. Description of the Related Art There have been various literatures on back pressure type ATM switches. For example, JP-A-8-223
No. 173, “Back pressure type ATM”
Switch "," Multistage Network with Multicast / Routing Congestion Feedback "disclosed in JP-A-9-247189, JP-A-10-3258
The "ATM switch control system" disclosed in Japanese Patent Application Laid-Open No. 5-65678 and the "ATM switching system and its traffic control method" disclosed in Japanese Patent Application Laid-Open No. H10-65678. However, no special consideration is given to broadcast cells in these documents.

[0003] Conventional cell traffic
Service priority (service class)
Per destination port (for individual destination cells and broadcast cells)
Queue the cell to the input side cell buffer (queuein
g) Then, when at least one of the destination output side cell buffers is congested, the output of the broadcast cell is stopped. That is, when a cell can be output to the most congested port among a plurality of destination ports, the cell is broadcasted to all the destination ports for the first time.

In such a conventional ATM switch, there is a problem that the temporary congestion of a specific port affects cells to other ports, and the delay time and delay time fluctuation of broadcast cells increase. In particular, when a plurality of ATM switches are connected in multiple stages and a plurality of ATM switches are broadcast-connected,
This problem becomes remarkable because the delay time of the worst route in the ATM switch at each stage is added. There is also a method of generating a plurality of individual destination cells by copying a broadcast cell in the input side cell buffer and outputting the plurality of individual destination cells to the N × N switch.
Establishing a broadcast connection of (ll rate) has a problem in that the throughput of the N × N switch is squeezed.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a conventional ATM.
An object of the present invention is to solve the above-described problem in a switch. That is, in the transmission of a broadcast cell, in a normal state, the broadcast cell is broadcast-outputted to all destination ports, and when a specific output port is congested, the broadcast cell is first output only to the other output ports. It is another object of the present invention to provide an ATM switch which can output to a congested port later so as not to affect the other destination port of the broadcast cell by the congested port.

[0006]

According to the present invention, a broadcast cell is queued to a queue for the broadcast cell.
g) If no back pressure signal is output from any destination port, the destination information is added as it is and the cell is output to the switch. If a back pressure signal is output from one or more destination ports, the back pressure signal is output. The cell with the destination port information rewritten so as to be output only to the destination port where no is output is output, and the cell with the destination port information rewritten so as to be output to the remaining destination ports is added to the head of the broadcast cell queue. And output after the back pressure signal is released.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the entire ATM switch. As shown in FIG.
Switch is the input side cell buffer (cell buffer memory)
It comprises 110 to 1N0, an N × N switch 200, and output-side cell buffers 310 to 3N0.

The input side cell buffers 110 to 1N0 are provided with a large-capacity memory (me
mory), and for each service class (service class),
In addition, cells are queued separately for each destination port. The destination port here is the output port of the N × N switch 200, that is, the output side cell buffers 310 to 3N0.

The output side cell buffers 310 to 3N0 have a large-capacity memory for traffic priority control, and queue cells separately for each service class and each destination port. The destination port here is the output side cell buffer 31
It is the outgoing line at the subsequent stage of 0-3N0. When the output port speed and the output line speed of the N × N switch 200 are the same, the number of destination ports is one.

FIG. 2 shows the input-side cell buffer 110 of FIG.
FIG. 3 is a block diagram illustrating a configuration example of FIG. However, in the example shown in FIG. 2, there are two service classes: a real time system and a non-real time system. The configuration of the other input-side buffers in FIG. 1 is the same as the configuration of the input-side buffer 110. The input cell is converted by the header conversion unit 112 into the input side connection table 1.
11, connection information is added, and distributed to each cell queue by a de-multiplexer 113.

A cell queue is provided for each service class and for each destination port. In the example of FIG.
Reference numerals 51 to 115n and 115x denote real-time cell queues, and cell queues 1161 to 116n and 116x denote non-real-time cell queues.
x and 116x are cell queues for broadcast cells. The cell queues 115x and 116x of the broadcast cell include broadcast cell output control units 118 and 119, respectively. The output of each cell queue (the output of the cell queue of a broadcast cell is output via a broadcast cell output control unit) is passed through an output cell selection control unit 117 to N.
It is input to the × N switch 200.

FIG. 3 is a format diagram showing the storage contents of the input-side connection table 111 of FIG. 1, and the VP described in the cell header of the cell.
I / VCI (VP identifier / VC identifier) (VP: Virtua
The destination port number (bitmap: bit map), service class, and internal connection number are stored for lPath, VC: Virtual Connection).

FIG. 4 is a block diagram showing an example of the configuration of the N.times.N switch 200 shown in FIG. 1. Cells from each input-side cell buffer are multiplexed by a cell multiplexing unit 201, and are transmitted to destination ports by cell filters 2021 to 202n. The number is checked (checked) and filtered (filtering)
The data is buffered and output by the cell buffers 2031 to 203n for each output port. Cell buffers 2031 to 203
n is controlled by the back pressure.

FIG. 5 shows the output side cell buffer 310 of FIG.
FIG. 3 is a block diagram illustrating a configuration example of FIG. However, in the example shown in FIG. 5, there are two service classes: a real-time system and a non-real-time system. The configuration of the other output-side cell buffer in FIG. 1 is the same as the configuration of the output-side cell buffer 310. The input cells are added with connection information by referring to the output side connection table 311 in the header conversion unit 312, and are distributed to each cell queue by the demultiplexer 313. The cell queue is provided for each service class and for each output line. In the example of FIG. 5, the cell queues 3151 and 3152 are real-time cell queues, and the cell queues 3161 and 3162 are non-real-time cell queues. The storage levels of these cell queues are monitored by the storage cell level monitoring unit 318 to determine the output of the back pressure signal. The output of each cell queue is output to each line via the output cell selection control unit 317.

FIG. 6 is a format diagram showing the storage contents of the output side connection table 311 of FIG. 5, and includes the outgoing line number, service class, VPI / VCI for outgoing line 0, and outgoing line 1 for each internal connection. VPI / VCI is stored.

The operation of the apparatus shown in FIGS. 1, 2, 4 and 5 will be described below. The header conversion unit 112 of the input-side cell buffer 110 performs VPI / VC of the header of the input cell.
According to I, the input side connection table 111 (FIG. 3)
And adds connection information such as a destination port number, a service class, and an internal connection number to the input cell. The demultiplexer 113 of the input-side cell buffer 110 distributes input cells to real-time cell queues 1151 to 115n and 115x and non-real-time cell queues 1161 to 116n and 116x according to the destination port number and service class added to the input cells.
The broadcast cell of the real-time system is queued to the cell queue 115x, and the broadcast cell of the non-real-time system is queued to the cell queue 116x.

The accumulation level monitoring section 318 (see FIG. 5) of each output side cell buffer outputs a back pressure signal to a non-real time system cell or a back pressure signal to all cells according to the cell accumulation level. Output to the N × N switch 200. The output cell selection control unit 117 of the input side cell buffer 110, based on the back pressure signal from the output side cell buffers 310 to 3N0, controls the real-time cell queues 1151 to 115n, 1
15x and non-real-time cell queues 1161-1
The cells to be output from 16n and 116n are selected. The output of the non-real-time cell to the port is stopped while the back pressure signal is being received to the non-real-time cell, and the output of all the cells to the port is stopped while the back pressure signal is being received to all the cells. In a queue group of real-time cells having a high service class, a cell to be output from a queue of a destination port not receiving a backpressure signal from an output side cell buffer of the destination port is selected and output to the N × N switch 200. I do.

The broadcast cell output control unit 118 issues a broadcast cell output request to the output cell selection control unit 117. If the broadcast cell output control unit 118 selects the output cell, the destination port number of the output cell and the back pressure from each output side cell buffer are output. Compare the signals and if there is no backpressure signal from all destination ports,
The cell is output to the N × N switch as it is, and if a backpressure signal is output from one or more destination ports, a rewritten destination port number is added so as to output only the destination port where no backpressure signal is output. Cell N
The cell to which the destination port number rewritten to be output to the × N switch and output to the remaining destination ports is added is left at the head of the broadcast cell queue, and the back pressure signal is released for the remaining cells. Later, a broadcast cell output request is issued to the output cell selection control unit 117 again.

When there is no cell to be output in the queue group of the real-time cell, a cell to be output by the same operation is selected in the queue group of the non-real-time cell.
Output to the × N switch 200.

In the N × N switch 200, the cell multiplexing unit 2
01, multiplex the cells from each input side cell buffer,
The destination port number added to the cell is checked by the cell filters 2021 to 202n, and filtering is performed so that only the cell that matches the corresponding output port number is passed.
Writing to the cell buffers 2031 to 203n for each output port, the output side cell buffer 31 of each destination port
The cell is output to 0 to 3N0 (see FIG. 1). During the reception of the back pressure signal from the output side cell buffer of the destination port to all the cells, the output of the cells is stopped.

The header conversion section 312 of the output side cell buffer 310 (FIG. 5) searches the output side connection table 311 according to the internal connection number added to the input cell, and finds outgoing line number, service class, output Connection information such as line VPI / VCI is added. Demultiplexer 31 of output side cell buffer 310
Reference numeral 3 denotes a real-time cell queue 31 for input cells according to the outgoing line number and service class added to the input cells.
51, 3152, non-real-time cell queue 316
1, 3162. The broadcast cell of the real-time system is queued to the queues 3151 and 3152, and the broadcast cell of the non-real-time system is queued to the queues 3161 and 3162 by adding the outgoing line VPI / VCI.

The output cell selection control unit 317 of the output side cell buffer 310 selects cells to be output from the real-time cell queues 3151 and 3152 and the non-real-time cell queues 3161 and 3162 based on the outgoing line speed. That is, a cell to be output from a real-time cell group having a high service class is selected and output to the outgoing line side. Output to the outgoing line.

FIG. 7 is an operation diagram for comparing the operation of the ATM switch of the present invention with the operation of the conventional ATM switch. Reference numerals 700 to 703 indicate the operation of the conventional ATM switch, and reference numerals 710 to 713 indicate the present invention. 1 shows the operation of the ATM switch. Reference numerals 700 and 710 indicate the input of a broadcast cell to the ATM switch, respectively, reference numerals 701 and 711 indicate output of cells to the outgoing line of No. 1, reference numerals 702 and 712 indicate output of cells to the outgoing line of No. 2, Reference numerals 703 and 713 indicate output of cells to the outgoing line of number 3, respectively. It is also assumed that the back pressure signal is output from the outgoing line of No. 1 for a certain period. In conventional equipment,
Broadcast cells are output to all outgoing lines after the back pressure is released. In the ATM switch of the present invention,
The broadcast cell is immediately output to the line without outputting the back pressure signal, and the broadcast cell is output only after the back pressure is released only to the outgoing line of No. 1 which outputs the back pressure signal.

[0024]

As described above, the ATM switch of the present invention normally broadcasts a broadcast cell to all destination ports and, when a specific output port is congested, only to other output ports. Output first, and output to the congested port after congestion is released, so it is possible to realize priority control of sibling cells with relatively simple control so as not to affect congestion on other destination ports effective.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an ATM switch.

FIG. 2 is a block diagram showing a configuration of an input-side cell buffer of the ATM switch according to the present invention.

FIG. 3 is a format diagram showing a format of an input connection table of FIG. 2;

FIG. 4 is a block diagram showing a configuration of an N × N switch of the ATM switch according to the present invention.

FIG. 5 is a block diagram showing a configuration of an output-side cell buffer of the ATM switch according to the present invention.

FIG. 6 is a format diagram showing a format of an output side connection table of FIG. 5;

FIG. 7 shows the operation of the ATM switch of the present invention and a conventional ATM switch.
It is an operation | movement figure which compares operation | movement of a switch.

[Explanation of symbols]

110-1N0 Input-side cell buffer 111 Input-side connection table 112 Header conversion unit 113 Demultiplexer 1151-115n, 115x Real-time cell queue 1161-116n, 116x Non-real-time cell queue 117 Output cell selection control unit 118, 119 Broadcast cell output control Unit 200 N × N switch 201 Cell multiplexing unit 2021 to 202n Cell filter 2031 to 203n Cell buffer 310 to 3N0 Output cell buffer 311 Output connection table 312 Header conversion unit 313 Demultiplexer 3151, 1152 Real-time cell queue 3161, 3162 Non real time System cell queue 317 Output cell selection controller 318 Storage cell level monitor

Claims (5)

(57) [Claims] 1. ATM (Asynchronous Transfer Mode)
An input-side cell buffer in which a switch is provided for each input port, an N × N switch,
And an output-side cell buffer provided for each output port. The output-side cell buffer sends back pressure to the input-side cell buffer according to the cell accumulation level.
e) output a signal, the input side cell buffer queues input cells separately for each service class and for each destination port, and based on the back pressure signal from the output side cell buffer of the destination port, the service class Means for queuing broadcast cells to be output to a plurality of destination ports in a cell queue for broadcast cells different from a cell queue for each destination port in an ATM switch for selecting cells to be output by priority control for each destination The cells queued in the broadcast cell cell queue include a back pressure signal from any of the output cell buffers of the output cell buffers corresponding to the plurality of destination ports to which the broadcast cells are to be output. When no is output, the destination port information is added as it is to the cell queued in the broadcast cell cell queue, and the Means for outputting to the N × N switch, wherein the cells queued in the broadcast cell cell queue are output from the output side cell buffer corresponding to a plurality of destination ports to which the broadcast cell is to be output among the output side cell buffers. When a back pressure signal is output from one or more of the cell buffers, the cell is output with the destination port information rewritten so as to be output only to the destination port where the back pressure signal is not output, and the cell is output to the remaining destination ports. The cell added with the destination information rewritten to be output is left at the head of the broadcast cell cell queue, and the head left cell is released from the back pressure signal from the output side cell buffer corresponding to the remaining destination port. Means for outputting after an ATM switch. 2. The ATM switch according to claim 1, wherein said broadcast cell queue includes a real-time broadcast cell queue and a non-real-time broadcast cell queue. Wherein the output of the cells queued in the ATM switch is started after the output of all the cells queued in the real-time broadcast cell queue is completed. 3. The ATM switch according to claim 1, wherein the input-side cell buffer provided for each input port uses data stored in an input-side connection table and uses a VPI / VCI described in a cell header of the input cell.
(VP identifier / VC identifier) (VP: Virtual Path, V
C: Virtual Connection), a header conversion unit that adds connection information such as a destination port number, a service class, and an internal connection number of the input cell to the cell header.
A demultiplexer for distributing and inputting to a cell queue provided for each service class; attached to each broadcast cell cell queue among the cell queues, all back pressure signals from the output side cell buffer are collected, and a corresponding broadcast A broadcast cell output control unit for controlling cell output from the cell cell queue; a back pressure signal from a corresponding output side cell buffer; and an output cell selection control unit for controlling cell output from each cell queue according to a service class. An ATM switch, characterized in that: 4. The ATM switch according to claim 1, wherein said N × N switch is provided for each destination port, for multiplexing all cells input from said input side cell buffer. An ATM switch comprising: a cell filter that allows only a destination port number of a destination port to pass a cell described in a cell header; and a cell buffer that temporarily stores an output of the cell filter. 5. The ATM switch according to claim 1, wherein the output-side cell buffer provided for each output port uses data stored in an output-side connection table and uses an internal connection number described in a cell header of an input cell. A header conversion unit that adds connection information such as the outgoing line number, service class, and outgoing line VPI / VCI of the input cell to the cell header. A cell output from the header converting unit is output for each outgoing line number.
A demultiplexer that sorts and inputs the cell queues provided for each service class, and a storage cell level monitoring unit that monitors the storage cell level of each cell queue of the cell queue and generates and outputs a back pressure signal for each cell queue. ATM switch.