JP2570642B2 - ATM cell switching equipment - 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 cell switching system and, more particularly, to a cell having a plurality of input ports and a plurality of outputs, and a fixed-length packet input from the plurality of input ports. The present invention relates to an ATM cell switching device for outputting from a desired output port based on address information.

[0002]

2. Description of the Related Art High-speed cell switching used for converting all information such as voice, data, and images into cells of fixed-length packets and transmitting and exchanging information at a very high speed using a simplified protocol. High interest in methods. In particular, a cell switching system having buffers on the input and output sides of a switching device has been proposed to suppress the cell loss rate when cells arrive in a burst. Cell switching used in such a high-speed cell switching system As a device, "ATM switch XA with expandable buffer capacity", which was announced by Fan et al. In IEICE technical report SSE93-6 in 1993.
TOM ”and the like. In these papers, the high-speed cell switching system is realized with a configuration as shown in FIG. FIG. 3 shows a case where there are two input ports and two output ports. This cell switching apparatus includes input buffers 200-1 and 200-2 corresponding to input ports 21 and 22, and input buffer control units 201-1 and 201-2 of each input buffer.
A time-division multiplexing bus 202 for time-division multiplexing the cells output from each input buffer;
And an output buffer control unit 203 for each output buffer.
-1, 203-2, and cells input from the input ports 21 and 22 are temporarily stored in the input buffers 200-1 and 200-2.
-2 stored in the output buffer control unit 203-
1, 203-2 monitors the accumulation state of the cells in the output buffer, and based on the information, the input buffer control unit 201
-1,201-2 are input buffers 200-1,200-
2 to select a cell destined for an output buffer having a free space, and outputs the selected cell to the time division multiplex bus 202. Time division multiplex bus 202
Are output to the address filters 204-1, 20.
At 4-2, the requested output ports 23 and 24 are checked, and only the corresponding cells are received and the output buffer 205-
1, 205-2.

[0003] The operation of the cell switching apparatus will be described. Cells input from the input ports 21 and 22 are temporarily stored in the input buffers 200-1 and 200-2. At this time, the input buffer 200- is used for each output port / traffic type.
Queue length management, which is the accumulated amount of cells in 1,200-2, is performed. Input buffer control units 201-1 and 201-2
Reference numeral 02-2 determines cells to be output from the input buffers 200-1 and 200-2 based on information from the output buffer control units 201-1 and 202-2 corresponding to each output port. Output buffer control units 201-1 and 202-2
Informs whether or not the cell can be received from the accumulation state of the buffer to be managed. Input buffer control unit 201-
1, 202-2 receives the storage state of the cells from each of the output buffer control units 203-1 and 203-2, and determines which output port 23 or 24 cell to output based on the information. Input buffers 200-1, 200-2
Are output to each of the address filters 204-1 and 204-2 by the time division multiplex bus 202, and only the cells destined for the output ports connected to the corresponding output buffers 205-1 and 205-2 are pulled in. The output buffers 205-1 and 205-2 accumulate the cells drawn by the address filters 204-1 and 204-2, and sequentially output the cells accumulating the earliest in accordance with the output line speed.

[0004]

SUMMARY OF THE INVENTION The conventional ATM described above.
In the cell switching method, the input buffer has a queue length (number of accumulated cells) in the buffer for each output port / traffic type.
Management and random in random out Ramdom
In Random Out (hereinafter referred to as RIRO)
Is required, and the input buffer unit must have complicated control. Therefore, there is a disadvantage that the control logic is increased and the cost is increased.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an ATM cell switching apparatus which solves the above-mentioned problems of the prior art, realizes control of an input buffer section in a simple manner, and has a reduced cost.

[0006]

An ATM cell switching apparatus according to the present invention comprises an input buffer unit provided for an input port, and an output buffer unit provided for an output port. A first address filter unit, a first collision avoidance buffer, a first arbiter unit, and a first collision absorption buffer. The first address filter unit is provided corresponding to each of the output buffer units. Receiving the cell input from the port, the address filter unit receives the received cell if the address filter unit corresponding to the desired output port of the received cell,
If the received cell is not an address filter unit corresponding to a desired output port of the received cell, the received cell is discarded, and the first
The collision avoidance buffers are provided in correspondence with the respective output buffer sections, accumulate the cells drawn by the first address filter section, and output the output request information of the cells stored first.
And outputs the earliest stored cell when the output-capable information is received from the first arbiter. The first arbiter outputs the congestion information from the output buffer corresponding to the output port. Receiving the output request information from the first collision avoidance buffer and the accumulated information from the first collision absorption buffer, and determining that the collision absorption buffer can be received from the accumulated information from the first collision absorption buffer; and When there is at least one first collision avoidance buffer installed corresponding to the output buffer unit determined to be not in the congestion state from the congestion information from the output buffer unit corresponding to the output port, and it is not in the congestion state. Output request information is output from one or more first collision avoidance buffers among one or more first collision avoidance buffers installed corresponding to the determined output buffer unit. One or more first collision avoidance buffers installed corresponding to the output buffer unit corresponding to the output port which is determined to be not in the congestion state from the congestion information when the communication is in communication; Is transmitted to the collision avoidance buffer, output enable information is transmitted to the collision avoidance buffer, a cell output from the collision avoidance buffer is received, the received cell is output to the first collision absorption buffer, and the first collision absorption buffer is The first arbiter unit accumulates the cells received from the first collision avoidance buffer, and when the number of accumulated cells exceeds a set threshold value, determines that congestion has occurred in the first arbiter unit and transmits congestion information. Transmitting, receiving the congestion information from the output buffer corresponding to the output port, and determining that the earliest accumulated cell is not in the congestion state from the congestion information from the output buffer corresponding to the output port. If desired cell output port connected to the output buffer unit has has a function of outputting the cell to said output buffer unit,
The output buffer unit includes a second address filter unit and a second address filter unit.
, An output collision avoidance buffer, a second arbiter circuit, and a second output collision absorption buffer, and a second address filter section is provided corresponding to each of the input buffer sections and connected to each of the input buffer sections. Receiving a cell input from the input buffer unit, and outputting the cell to the second collision avoidance buffer if the received cell is a cell that desires an output port connected to the output buffer unit; If a cell other than the desired output port is desired, the cell is discarded, and the second collision avoidance buffer stores the cell drawn in by the second address filter unit, and outputs the output request information of the cell stored the earliest to the second arbiter unit. And outputs the earliest stored cell when receiving the output enable information from the second arbiter unit, and outputs the input when the number of stored cells exceeds a set threshold. The first arbiter unit of Ffa portion and the first
The second arbiter unit receives the output request information from the second collision avoidance buffer and the accumulated information from the second collision absorption buffer, and transmits the congestion information assuming that congestion has occurred in the second collision absorption buffer. When it is determined from the stored information from the collision avoidance buffer that the collision avoidance buffer is receivable, the output from the second collision avoidance buffer making an output request is 1
Selecting the collision avoidance buffers, transmitting output enable information to the collision avoidance buffer, receiving cells output from the second collision avoidance buffer, outputting the received cells to a second collision absorption buffer, The second collision absorbing buffer accumulates cells received by the second arbiter from the second collision avoidance buffer, and congestes the second arbiter when the number of accumulated cells exceeds a set threshold. Has the function of transmitting congestion information assuming that an error has occurred, and sequentially outputting the stored cells from the earliest stored cell in accordance with the speed of the output port.

Also, the first arbiter of the input buffer is determined to be not in the congestion state from the congestion information. The output buffer corresponding to the output port is determined to be not in the congestion state from the output buffer corresponding to the output port. Selecting one collision avoidance buffer from the one or more first collision avoidance buffers in which cells desired for the connected output port are stored, transmitting output enable information to the collision avoidance buffer,
, Which controls the reception of cells output from the collision avoidance buffer a plurality of times during the transmission time of one cell at the input port or output port.

The second arbiter unit of the output buffer unit selects one collision avoidance buffer from the second collision avoidance buffers requesting the output, and transmits output enable information to the collision avoidance buffer. The control includes receiving the cell output from the second collision avoidance buffer a plurality of times during the transmission time of one cell at the input port or the output port.

The first collision absorbing buffer of the input buffer unit receives the congestion information from the output buffer unit corresponding to the output port, and the cell which has accumulated the earliest is the congestion information from the output buffer unit corresponding to the output port. If it is determined that the output port connected to the output buffer unit is not in a congestion state, the control to output the cell to the output buffer unit is performed for the transmission of one cell at the input port or the output port. Including one that is performed several times in a time.

[0010]

A collision avoidance buffer and a collision absorption buffer are dispersedly arranged in an input buffer section and an output buffer section, and a back pressure is applied to a buffer immediately preceding the collision avoidance buffer and the collision absorption buffer and a buffer preceding the previous buffer. Since control is applied, congestion occurs due to bursts of cells destined for the same port arriving for the cells destined for the output port, the number of accumulations increases, and the number of cells discarded for other output ports increases. To the random in random out (RIR)
Instead of the control of O), it can be realized by simple first-in first-out First In First Out (hereinafter referred to as FIFO) control.

[0011]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of an input buffer unit of the ATM cell switching device of the present invention, and FIG. 2 is a block diagram of an output buffer unit of the ATM cell switching device of FIG.

The ATM cell switching apparatus has input ports 11 and 12 to which a packet is input, and input ports 11 and 1 respectively.
2, input buffer units 104 and 114 whose inputs are connected to respective input ports, and output port 1
3 and 14, and output buffer units 124 and 134 whose inputs are connected to the outputs of all the input buffer units 104 and 114, respectively.
The configuration of each unit will be described below.

The input buffer unit 104 includes the address filters 100-1 and 100-2 and the collision avoidance buffer 101-
1, 101-2, arbiter 102, and collision absorption buffer 1
03, the input buffer unit 114 includes the address filters 110-1 and 110-2 and the collision avoidance buffer 111.
-1, 111-2, an arbiter unit 112, and a collision absorption buffer 113. Here, the input buffer unit 104 will be described as an example.

Address filters 100-1 and 100-2
Checks the destination of the cell input from the input port 11, receives the cell if the own address filter corresponds to the desired output port, outputs the cell, and outputs the cell to another port. If it is a cell of, discard it.

The collision avoidance buffers 101-1 and 101-2
Are the address filters 100-1 and 100-, respectively.
2 and the input is an address filter 100
-1 and 100-2 and the cells output from the address filters 100-1 and 100-2 are stored if there is a free capacity, otherwise discarded and stored, as connected to the arbiter unit 102 at the subsequent stage. If there is, the output request information is output to the arbiter unit 102 at the subsequent stage, and when the output available information is received from the arbiter unit 102, the cell that has accumulated the earliest is output.

The arbiter unit 102 receives input from each of the collision avoidance buffers 101-1 and 101-2 and the collision absorption buffer 10
3 is connected to the collision avoidance buffers 121-1 and 131-1 of the output buffer units 124 and 134. The output request information from the collision avoidance buffers 101-1 and 101-2 and the congestion information of the collision absorption buffer 103. Avoidance buffers 121-1 and 13 of the output buffer units 124 and 134
When it is determined from the congestion information from 1-1 that the collision absorption buffer 103 is not congested (the number of accumulated cells does not exceed the set threshold) and the collision avoidance buffer 1
21-1 and 131-1 select the output buffer units 124 and 134 that are not congested, and the collision avoidance buffer 1 storing cells destined for the selected output buffer units.
When an output request has been made from 01-1, 101-2, one of the collision avoidance buffers 101-1 and 101-2 is selected from the collision avoidance buffers 101-1 and 101-2, and the collision avoidance buffer 101 is selected. -1, 101-2, and outputs the output enable information to the collision avoidance buffers 101-1 and 101-.
2 and outputs the cells to the subsequent collision absorption buffer 103.

The collision absorbing buffer 103 has an input connected to the arbiter unit 102 and the collision avoiding buffers 121-1 and 131-1 of the output buffer units 124 and 134.
The cells output from the arbiter unit 102 are accumulated, and when the number of accumulated cells exceeds a set threshold value, the congestion information is transmitted to the arbiter unit 102. Output buffer unit 12 connected
4,134 collision avoidance buffers 121-1 and 131-1
Is determined to be in a non-congested state based on the congestion information from the collision avoidance buffers 121-1 and 131-1 of the output buffer units 124 and 134, and outputs the earliest accumulated cells.

The input buffer 104 is an arbiter 102
Control of the collision avoidance buffers 101-1 and 101-2 and the corresponding collision avoidance buffers 101-1 and 101-2
The cell output control from 1-2 can be performed a plurality of times within the time for transmitting one cell at the input port or output port (bit length of cell / line speed).

The input buffer unit 104 can perform the cell output operation from the collision absorbing buffers 101-1 and 101-2 a plurality of times during the transmission of one cell at the input port or the output port. .

The output buffer unit 124 includes the address filters 120-1 and 120-2 and the collision avoidance buffer 121-
1, 121-2, an arbiter unit 122, and a collision absorption buffer 123. The output buffer unit 134 includes the address filters 130-1 and 130-2 and the collision avoidance buffer 13.
1-1, 131-2, an arbiter section 132, and a collision absorption buffer 133. Here, the output buffer section 124 will be described as an example.

Address filters 120-1 and 120-2
Is connected to the collision absorption buffers 103 and 113 of the input buffer units 104 and 114, and if the cell output from the collision absorption buffers 103 and 113 is the output buffer unit 124 corresponding to the desired output port, the cell And outputs the received cell to the subsequent collision avoidance buffers 122-1 and 122-2. If the cell is not the output buffer unit 124 corresponding to the desired output port, the cell is discarded.

The collision avoidance buffers 121-1 and 121-2
Has inputs connected to the address filter units 120-1 and 120-1, and the address filter units 120-1 and 120-1
The cells output from 0-2 are accumulated, and when the number of accumulated cells exceeds a set threshold value, the congestion information is set to a congestion state and collides with the arbiter units 102 and 112 of the input buffer units 104 and 114. The data is transmitted to the absorption buffers 103 and 113.

The arbiter unit 122 receives input from the collision avoidance buffers 121-1 and 121-2 and the collision absorption buffer 124.
And each of the collision avoidance buffers 121-1 and 121-1
21-2, output possible information only when it is determined from the output request information and the congestion information of the collision absorption buffer 123 that the collision absorption buffer 123 is not congested (the number of accumulated cells does not exceed the set threshold). Is selected from among the collision avoidance buffers 121-1 and 121-2 that output
Outputtable information is transmitted to the collision avoidance buffers 121-1 and 121-2, and the collision avoidance buffers 121-1 and 121-1 are output.
The cell output from 21-2 is received, and the cell is output to the collision absorption buffer 123 in the subsequent stage.

The collision absorbing buffer 123 has an input connected to the arbiter unit 122, stores cells output from the arbiter unit 122, and becomes congested when the number of stored cells exceeds a set threshold. The information is transmitted to the arbiter unit 122, and the cell that has accumulated the earliest is output to the output port in accordance with the line speed of the output port.

The output buffer units 124 and 134 perform the operation of selecting the collision avoidance buffer of the arbiter unit and the operation of outputting the cell from the collision avoidance buffer a plurality of times during the transmission of one cell at the input port or output port. It is also possible to do.

The collision avoidance buffers 101-1, 101-2, 111-1, and 111 of the input buffer units 104 and 114
-2, the collision avoidance buffers 121-1 of the collision absorption buffers 103 and 113 and the output buffer units 124 and 134.
121-2, 131-1 and 131-2, and cell accumulation and output control of the collision absorption buffers 123 and 133 are performed in such a manner that when the output permission is obtained from the buffer and the arbiter unit at the subsequent stage, the cells are sequentially output from the earliest accumulated cells. The basic operation is based on the principle described above.

Cells input from the input port are input buffer units 104 and 114 and output buffer unit 12.
4,134 address filters 100-1, 100-
2,110-1,110-2,120-1,120-
The destinations are checked at 2, 130-1 and 130-2, and are sequentially stored in a buffer corresponding to a desired destination, thereby being replaced with a desired output port.

The arbiter unit 102 of the input buffer unit 104
Is not only the congestion information of the collision absorption buffer 103 in the input buffer unit 104 immediately downstream, but also the output buffer unit 1
24, 134 collision avoidance buffers 121-1, 121-
2, 131-1 and 131-2 to obtain the congestion information, and the collision avoidance buffers 101-1 and 101- of the input buffer unit 104.
2 to the collision absorption buffer 103.
This control causes congestion due to bursts of cells destined for the same port arriving at the output port.
Since the cells wait at 1-2, the congested cells destined for the output port occupy the collision absorption buffers 103 and 113 of the input buffer units 104 and 114, and the cells destined for the other output ports are occupied by the collision absorption buffers 103 and 113. The waiting time in the collision avoidance buffers 101-1 and 101-2 increases, and the collision avoidance buffers 101-1 and 101-2 increase the waiting time.
-2 disappears, and the effect of cell discarding can be suppressed.

[0030]

As described above, according to the present invention, the collision avoiding buffer and the collision absorbing buffer distributed in the input buffer unit and the output buffer unit are used to back up the immediately preceding buffer and the buffer preceding the immediately preceding buffer. By applying pressure control, every time a cell destined for the same port arrives in a burst, the number of cells waiting for a congested output port increases and the number of accumulated cells increases, and the number of cells discarded for other output ports increases. Since this can be realized by simple FIFO control, the control logic can be reduced, the structure can be simplified, and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram of an input buffer unit of an ATM cell switching device according to the present invention.

FIG. 2 is a block diagram of an output buffer unit of the ATM cell switching device of FIG.

FIG. 3 is a block diagram of a conventional example of an ATM cell switching device.

[Explanation of symbols]

11, 12 input port 13, 14 output port 100-1, 100-2, 110-1, 110-2, 1
20-1, 120-2, 130-1, 130-2 Address filters 101-1, 101-2, 111-1, 111-2, 1
21-1, 121-2, 131-1, 131-2 Collision avoidance buffer 102, 112, 122, 132 Arbiter unit 103, 113, 123, 133 Collision absorption buffer 104, 114 Input buffer unit 124, 134 Output buffer unit

Claims (4)

(57) [Claims] 1. A cell having a plurality of input ports and a plurality of output ports, wherein a cell which is a fixed-length packet input from the plurality of input ports is transmitted from a desired output port based on address information of the cell. An output ATM cell switching device, comprising: an input buffer unit installed corresponding to the input port; and an output buffer unit installed corresponding to the output port, wherein the input buffer unit has a first address filter unit and a first address filter unit.
A collision avoidance buffer, an arbiter unit, and a first collision absorption buffer, wherein a first address filter unit is provided corresponding to each of the output buffer units, receives a cell input from the input port, If the address filter unit is an address filter unit corresponding to a desired output port of the received cell, the received cell is received. If the address filter unit is not an address filter unit corresponding to a desired output port of the received cell, the received filter is not received. The first collision avoidance buffer is disposed in correspondence with each of the output buffer units, accumulates cells drawn by the first address filter unit, and outputs the output request information of the earliest accumulated cell. 1 arbiter unit, and outputs the earliest accumulated cell when the output enable information is received from the first arbiter unit. Receiving the congestion information from the output buffer unit corresponding to the input port, the output request information from the first collision avoidance buffer, and the accumulated information from the first collision absorption buffer; When the absorption buffer is determined to be receivable and the first collision avoidance buffer installed corresponding to the output buffer unit determined not to be in the congestion state from the congestion information from the output buffer unit corresponding to the output port, Output from one or more first collision avoidance buffers among one or more first collision avoidance buffers installed corresponding to the output buffer unit determined to be not congested when there is at least one. One or more installed corresponding to the output buffer unit corresponding to the output port, which is determined not to be in the congestion state from the congestion information when receiving the request information One collision avoidance buffer is selected from the first collision avoidance buffer, output enable information is transmitted to the collision avoidance buffer, a cell output from the collision avoidance buffer is received, and the reception is performed by the first collision absorption buffer. The first collision absorbing buffer accumulates cells received by the first arbiter unit from the first collision avoidance buffer, and outputs the first collision absorbing buffer when the number of accumulated cells exceeds a set threshold. Transmitting congestion information assuming that congestion has occurred in one arbiter unit, receiving congestion information from an output buffer unit corresponding to the output port,
If the earliest accumulated cell is the desired cell for the output port connected to the output buffer unit determined to be not in the congestion state from the congestion information from the output buffer unit corresponding to the output port, the output buffer unit Outputting a cell, wherein the output buffer unit includes a second address filter unit and a second address filter unit.
A collision avoidance buffer, a second arbiter circuit, and a second collision absorbing buffer. A second address filter unit is provided corresponding to each of the input buffer units, and connected to each of the input buffer units. Receiving a cell input from the input buffer unit, and outputting the cell to the second collision avoidance buffer if the received cell is a cell that desires an output port connected to the output buffer unit; If a cell other than the desired output port is desired, the cell is discarded. The second collision avoidance buffer stores the cell drawn in by the second address filter unit, and outputs the output request information of the cell stored earlier to the second arbiter unit. And outputs the earliest stored cells when receiving the output enable information from the second arbiter unit, and when the number of stored cells exceeds a set threshold value, the input buffer. The first arbiter unit and the first collision absorbing buffer of the phasing unit transmit congestion information assuming that congestion has occurred, and the second arbiter unit outputs output request information from the second collision avoidance buffer and the second collision absorbing buffer. Receiving one of the collision avoidance buffers from the second collision avoidance buffer that is receiving the accumulated information from the buffer and making an output request when it is determined from the accumulated information from the second collision avoidance buffer that the collision avoidance buffer is receivable; Selecting a buffer, transmitting output enabled information to the collision avoidance buffer, receiving cells output from the second collision avoidance buffer, outputting the received cells to a second collision absorption buffer, The absorbing buffer stores cells received by the second arbiter unit from the second collision avoidance buffer, and congestion occurs in the second arbiter unit when the number of stored cells exceeds a set threshold. Transmits congestion information as, ATM cell switching device characterized by having a function of sequentially outputting the earliest accumulated cells in accordance with the speed of the output ports. 2. A method according to claim 1, wherein the first arbiter section of the input buffer section determines that the first arbiter section is not in the congestion state from the congestion information. Selecting one collision avoidance buffer from the one or more first collision avoidance buffers in which cells desired for the connected output port are stored, transmitting output enable information to the collision avoidance buffer, 2. The ATM cell switching apparatus according to claim 1, wherein control for receiving a cell output from the collision avoidance buffer is performed a plurality of times within a transmission time of one cell at an input port or an output port. A second arbiter unit of the output buffer unit selects one collision avoidance buffer from the second collision avoidance buffers requesting the output, and transmits output enable information to the collision avoidance buffer; 3. The ATM cell switching device according to claim 1, wherein control for receiving a cell output from the second collision avoidance buffer is performed a plurality of times within a transmission time of one cell at an input port or an output port. 4. A first collision absorption buffer of an input buffer unit receives congestion information from an output buffer unit corresponding to the output port, and a cell stored first stores congestion information from an output buffer unit corresponding to the output port. If it is determined that the output port connected to the output buffer unit is not in a congestion state, the control to output the cell to the output buffer unit is performed for the transmission of one cell at the input port or the output port. 4. The ATM cell switching device according to claim 1, wherein the ATM cell switching is performed a plurality of times during a time period.