JPH04314235A - cell exchange device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention is a wideband ISDN (Integrated Services Digital Network) based on the ATM (Asynchronous Transfer Mode) system. This invention relates to a cell switching device that performs priority control for discarding information (divided transmission unit of information consisting of).

0002

[Prior Art] For example, literature (Kozaki et al.: LSI configuration method for common buffer type ATM switch, 1989 IEICE Technical Report, S
In the conventional common buffer cell switching device shown in SE89-144), as shown in FIG.
n is connected to the common buffer section 2a. Common buffer section 2
a commonly uses the buffer area, and input cell connection section 1a
The write address command 40 of the control section 4a holds the multiplexed input cell from 1, and the read address command 50 of the control section 4a reads out the multiplexed output cell to the output connection section 3a. On the other hand, the reserved cell address is first in, first out (F
IFO) operation. The output cell connection section 3a separates the output cells 20 using a demultiplexer and connects the common buffer section 2a to a plurality of output lines 1 to n. The control unit 4a is provided with a cell discard uniform priority control means, decodes the header information (outgoing line destination information and cell discard priority information) 30 of the input cell from the input cell connection unit 1a, and performs uniform input cell discard priority control. Then, write and read address commands 40 and 50 are issued to the common buffer section 2a. On the other hand, the newly written address 60 is added to the end of the reserved cell addresses in the common buffer section 2a, and the addresses 70 sequentially read from the beginning of the reserved cell addresses are treated as unused addresses.

The above conventional common buffer type cell switching device discards input cells 10 by dividing them into priority cells (cells that are strict against discarding data communication information, etc.) and non-priority cells (cells that are lenient with respect to discarding image information, etc.). A method of uniform priority control for each cell (uniform cell discard priority control method) is adopted.

[0004] As shown in FIG. 11, the cell discard uniform priority control means of the control unit 4a first outputs the respective count signals 11 and 12 of the priority cells and non-priority cells held in the common buffer unit 2a to the respective count signals 11 and 12 of the priority cells and non-priority cells. Counters 5 and 6 respectively count. Next, each count value of each counter 5 and 6 of a priority cell and a non-priority cell is multiplied by each comparator 7 and 8 of a priority cell and a non-priority cell.
and Y with predetermined thresholds (X>Y), and outputs respective discard command signals 13 and 14 so as to discard priority cells and non-priority cells exceeding the respective thresholds.

[0005]

[Problem to be Solved by the Invention] In the conventional cell switching device as described above, there is a method (cell discard uniform priority control method) in which the discard of input cells is uniformly prioritized and controlled for each priority cell and non-priority cell. Therefore, if the ratio of non-priority cells is high, there is sufficient buffer space, but non-priority cells that exceed a threshold are discarded, resulting in the problem that the buffer space cannot be used effectively.

[0006] The problem to be solved by this invention is to conditionally control the discarding of input cells to only non-priority cells in a cell switching device, to satisfy the required quality for discarding priority cells, and to discard non-priority cells. The object of the present invention is to provide a method (cell discard condition priority control method) that can effectively use a buffer area without discarding more cells than necessary.

[0007]

[Means for Solving the Problems] In order to solve the above problems, the cell switching device of the present invention is characterized by having the following means and adopting a cell discard condition priority control system.

The input cell connection section and the output cell connection section connect a plurality of incoming lines to a buffer section, and connect the buffer section to a plurality of outgoing lines.

The buffer section writes and holds input cells from the input cell connection section in response to a write address command from the control section, and reads out output cells to the output cell connection section in response to a read address command from the control section. On the other hand, addresses of reserved cells are held in correspondence with outgoing lines by FIFO operation.

The control unit is provided with a cell discard condition priority control means, which decodes the header information (outgoing line destination information and cell discard priority information) of the input cell from the input cell connection unit, and performs condition priority control for input cell discard. and commands the write/read address to the buffer section. On the other hand, the newly written address is added to the end of the reserved cell addresses in the buffer section, and the addresses sequentially read from the beginning of the reserved cell addresses are treated as unused addresses.

The cell discard condition priority control means overwrites the input priority cell with the address of the reserved non-priority cell only when the buffer section is full of reserved cells, and controls so that the overwritten address is not read twice. Discard the cell. Also, the number of reserved cells in the buffer section is counted and non-priority cells are discarded only when a predetermined condition is met. Also, the number of reserved cells and the number of reserved cell addresses in the buffer section are counted, and non-priority cells are discarded only when respective predetermined conditions are satisfied.

0012

[Operation] The cell switching device of the present invention uses the above means to perform conditional priority control on input cells on a plurality of incoming lines, discard non-priority cells, effectively use buffer area, and output cells on a plurality of outgoing lines. Determine.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A divided common buffer type cell switching device according to an embodiment of the present invention is shown in FIG. 1, which corresponds to the conventional example shown in FIG. 10. However, input cell connection part 1 and output cell connection part 3
routes the input cell 10 and output cell 20 using a space switch. The divided common buffer section 2 divides the buffer area and uses it commonly. The control unit 4 is provided with a cell discard condition priority control means and performs condition priority control for discarding input cells.

The divided common buffer type cell switching device of the above embodiment adopts a method (cell discard condition priority control method) in which discarding input cells 10 is conditionally controlled with priority only for non-priority cells.

As shown in FIG. 2, the cell discard condition priority control means of the control section 4 overwrites the input priority cell with the address of the reserved non-priority cell only when the divided common buffer section 2 is full of reserved cells, and uses the overwritten address. is controlled so that it is not read twice, and the non-priority cell is discarded. First, the non-priority cell address determination and reserved cell address format generation means 11 determines the write address 11 of the reserved cell from the cell discard priority information (priority/non-priority determination bit) 120 of the input cell header.
0 and holds the non-priority cell address in the non-priority cell address buffer 12. On the other hand, a format is generated in which a priority/non-priority determination bit is added to the write address 110 of the reserved cell, and the format is set as the reserved cell end address 60 of the divided common buffer unit 2. Next, with the input priority cell overwrite command 150 when the reserved cells of the divided common buffer unit 2 are full, the non-priority cell address from the non-priority cell address buffer 12 is set as the input priority cell overwrite address 130, and is held in the overwrite address buffer 13 at the same time. do. Furthermore, from the reserved cell start address 70 of the divided common buffer section 2, overwritten addresses in the overwritten address buffer 13 referred to by the overwritten address invalidating means 14 and having a non-priority determination bit are determined and invalidated, and the addresses that have not been overwritten are invalidated. is set as the read address 140 of the reserved cell after absorbing the difference between the speed at which the address is invalidated and the speed at which the reserved cell is read in the speed adjustment buffer 15. Note that the speed at which addresses are invalidated is set several times the speed at which reserved cells are read, so that the throughput will not decrease due to the vacant space in reading reserved cells even if the addresses are invalidated. Furthermore, when an address is invalidated, the address is deleted from the overwrite address buffer 13.

In the above embodiment, the means for controlling to prevent the overwritten address from being read twice may be as shown in FIG. First, the non-priority cell address determination and address format generation means 11a determines the write address 110 of the reserved cell from the header information (outgoing destination information and cell discard priority information) 30 of the input cell, and sets the outgoing destination to the non-priority cell address. A format with a number and own pointer value (position where own address is written) is generated and held in the non-priority cell address buffer 12. On the other hand, a format is generated in which a previous pointer value (the position where the previous address is written) and a subsequent pointer value (the position where the next address is written) are added to the write address 110 of the reserved cell. Next, with an input priority cell overwrite command 150 when the reserved cells of the divided common buffer section 2 are full, the non-priority cell address from the non-priority cell address buffer 12 is set as the input priority cell overwrite address 130. Further, the pending cell address format conversion means 16 receives the outgoing line destination number and own pointer value of the overwrite address 130 from the non-priority cell address buffer 12, and receives the write address 11 of the pending cell.
Convert the generation format of 0 and divide common buffer section 2.
The last address of the reserved cell is 60. For example, when receiving n as the outgoing destination number and 7 as the own pointer value of the overwriting address 130, the previous pointer value 6 at the position indicated by the own pointer value 7 of the reserved cell address of the outgoing destination number n
and the rear pointer value 8 is read, and the rear pointer value 7 of the position indicated by the previous pointer value 6 is rewritten to 8. In this way, the post-pointer value is rewritten and the overwrite address 130 is skipped and read.

In the above embodiment, the cell discard condition priority control means of the control section 4 counts the number of reserved cells in the divided common buffer section 2 and discards non-priority cells only when a predetermined condition is met, as shown in FIG. You can. First, the reserved cell count signal 210 of the divided common buffer unit 2 is counted by the reserved cell counter 21, the counted value is compared with a predetermined threshold value by the reserved cell comparator 22, and the header information (cell discard priority information) 30 of the input cell is
is decoded by the header decoder 23. Next, a cell discard determining means 24 makes a decision based on the results of the reserved cell comparator 22 and header decoder 23, and outputs a cell discard command signal 220 so as to discard only non-priority cells exceeding a threshold value.

In the above embodiment, the reserved cell comparator 22 and the cell discard determination means 24 compare the counted value with a predetermined threshold value using a plurality of reserved cell comparators 22a, in which the threshold value A is larger than the threshold value B, as shown in FIG. First, the cell discard determining means 24a may output a cell discard command signal 220 so that non-priority cells exceeding threshold B are discarded at a predetermined frequency, and all non-priority cells exceeding threshold A are discarded. Further, the reserved cell comparator 22a may perform precise control by increasing the number of used cells and the threshold value, or may monitor the input ratio of priority cells and non-priority cells, and set a dynamically changing threshold value.

Further, in the above embodiment, the cell discard condition priority control means of the control section 4 counts the number of reserved cells and the number of reserved cell addresses in the divided common buffer section 2, and only when respective predetermined conditions are satisfied, as shown in FIG. Non-priority cells may be discarded. First, the reserved cell counter 21, the reserved cell comparator 22a, and the header decoder 23 are the same as those in FIG. 25, and each count value is counted by each reserved cell address comparator 26 corresponding to the outgoing line.
is compared with a predetermined threshold value. Next, the reserved cell comparator 22a
Based on the results of each reserved cell address comparator 26 and header decoder 23 corresponding to the outgoing line, the cell discard determination means 24b makes a determination as shown in FIG. A discard command signal 220 is output. As shown in FIG.
is a priority cell, it is not discarded unconditionally (steps S1, S
6). Next, in the case of a non-priority cell, the reserved cell comparator 22a
If it exceeds threshold A, it is discarded, and if it does not exceed threshold B, it is not discarded (steps S2, S3, S5, S6). Furthermore, if the non-priority cell exceeds the threshold B without exceeding the threshold A of the reserved cell comparator 22a, the outgoing line destination that exceeds the threshold of each reserved cell address comparator 26 corresponding to the outgoing line is discarded and is not exceeded. The outgoing line destination is not discarded (steps S4 to S6). Note that each reserved cell address comparator 26 corresponding to an outgoing line may set a different threshold value.

In the above embodiment, each reserved cell address comparator 26 and cell discard determination means 24b corresponding to the outgoing line calculates each count value of each reserved cell address counter 25 by the reserved cell address comparator 26a, as shown in FIG. They are compared with each other, and when the non-priority cell exceeds the threshold B of the reserved cell comparator without exceeding the threshold A of the non-priority cell as shown in FIG. It may be determined that the outgoing line destination with the maximum count value is discarded, and the other outgoing line destinations are not discarded (steps S4a, S5, and S6). Further, the reserved cell address comparator 26a may output order information of the counted values instead of the maximum counted values compared with each other for determination.

Although the cell switching device in the above embodiment has been explained as a divided common buffer type, it is also applicable to a common buffer type, an input buffer type, an output buffer type, etc., except for the common buffer type, FIGS. 6 and 8 of the above embodiment. Not even.

[0022]

[Effects of the Invention] The cell switching device of the present invention as described above adopts a method (cell discard condition priority control method) in which the discard of input cells is conditionally prioritized and controlled only for non-priority cells.
This has the effect of satisfying the required quality for discarding priority cells and effectively using the buffer area without discarding non-priority cells more than necessary.

[Brief explanation of drawings]

FIG. 1 is a functional block diagram of a cell switching device according to an embodiment of the present invention.

FIG. 2 is a functional block diagram of an embodiment of cell discard condition priority control means of the control unit shown in FIG. 1;

FIG. 3 is a functional block diagram of another embodiment of the cell discard condition priority control means shown in FIG. 2;

FIG. 4 is a functional block diagram of another embodiment of cell discard condition priority control means of the control unit shown in FIG. 1;

FIG. 5 is a functional block diagram of another embodiment of the cell discard condition priority control means shown in FIG. 4;

FIG. 6 is a functional block diagram of another embodiment of cell discard condition priority control means of the control unit shown in FIG. 1;

FIG. 7 is a flow diagram of the cell discard determination means shown in FIG. 6;

FIG. 8 is a functional block diagram of another embodiment of the cell discard condition priority control means shown in FIG. 6;

FIG. 9 is a flow diagram of the cell discard determination means shown in FIG. 8;

FIG. 10 is a functional block diagram of a conventional cell switching device.

FIG. 11 is a functional block diagram of cell discard uniform priority control means of the control unit shown in FIG. 10;

[Explanation of symbols]

1 Input cell connection section 2 Division common buffer section 3 Output cell connection section 4 Control section 10 using cell discard condition priority control method
Input cell 20 Output cell 30 Input cell header information 40 Write address command 50 Read address command 60 Pending cell end address 70 Pending cell first address

Claims (3)

[Claims] 1. An input cell connection section that connects a plurality of input lines to a buffer section, and an input cell connection section through which an input cell is written and held in response to a write address command from a control section, and an output cell is written to and held in response to a read address command from the control section. a buffer unit that reads the address of the reserved cell to the output cell connection unit and holds the address of the reserved cell in a first-in, first-out operation corresponding to the outgoing line; an output cell connection unit that connects the buffer unit to a plurality of outgoing lines; It decodes the header information of the input cell, prioritizes discarding the input cell, issues a write/read address command to the buffer section, adds the newly written address to the end of the reserved cell address in the buffer section, and discards the reserved cell. In the cell switching device, the cell switching device includes a control unit that treats addresses sequentially read from the beginning of addresses as unused addresses, in which the control unit converts input priority cells to addresses of reserved non-priority cells only when the buffer unit is full of reserved cells. 1. A cell switching device comprising a cell discard condition priority control means for overwriting and controlling the overwritten address so as not to read it twice and discarding the non-priority cell. 2. Cell exchange according to claim 1, further comprising cell discard condition priority control means for counting the number of reserved cells in the buffer section in the control section and discarding non-priority cells only when a predetermined condition is satisfied. Device. 3. A cell discard condition priority control means for counting the number of reserved cells and the number of reserved cell addresses in the buffer section in the control section and discarding non-priority cells only when respective predetermined conditions are satisfied. Item 1. Cell switching device according to item 1.