KR100387131B1 - Method and Device for Matching Cell in Asynchronous Transfer Mode Switching Exchange - Google Patents

Abstract

The present invention relates to a cell matching method and apparatus in an asynchronous transmission mode switch, wherein the matching method designates one frame unit as 56 clocks when transmitting cell data to a subscriber board through a cell bus, so that one clock receives two bytes of cell data. Transmitting the cell data to the cell matching device by repeating the transmission and not transmitting the cell data of 2 bytes in the next clock; Storing the two bytes of cell data received by the cell matching device receiving the transmitted cell data in a cell memory and increasing the write pointer by one; Comparing the write pointer with a read pointer to determine whether there is cell data to be transmitted; Reading the stored two bytes of cell data from the cell matching device using a clock in which cell data is not stored and incrementing the read pointer by one; And transmitting the read cell data to a subscriber transmission device, wherein the matching device designates one frame unit as 56 clocks so that one clock transmits two bytes of cell data and the next clock is two bytes. A cell bus for repeatedly transmitting data in a manner that does not transmit cell data of the cell bus; The memory write unit receives cell data from the cell bus to determine whether the cell data belongs to a corresponding subscriber board, and stores the received 2 bytes of cell data in a cell memory when the cell belongs to a corresponding subscriber board. ; A memory read unit which reads two bytes of cell data stored in the cell memory using a clock in which no data is stored in the cell memory; A memory controller configured to control the use of the cell memory of the memory lead unit and the memory write unit; A memory pointer for determining whether there is cell data to be transmitted by recording a pointer read or stored when reading or storing cell data in the memory read unit and the memory write unit; And a subscriber transmitter matching unit for transmitting the cell data read in the unit of 2 bytes from the memory read unit to the subscriber transmitter.

According to the method and apparatus according to the present invention, when transmitting cell data to a subscriber transmission device, it is possible to reduce the size of a storage space of data to be stored in a cell matching block and to improve cell delay.

Description

Method and Device for Matching Cell in Asynchronous Transfer Mode Switching Exchange}

The present invention relates to a cell matching method and apparatus in an asynchronous transfer mode switch (hereinafter, referred to as "ATM"), and more particularly, to modifying the cell transfer method from cellbus to subscriber board in a limited speed. The present invention relates to a cell matching method apparatus suitable for transmitting a large amount of cells in an apparatus.

In ATM, service information is transmitted by a continuous flow of packets having a constant size. Such fixed size packets are called ATM cells. The ATM cell consists of 53 bytes, of which 5 bytes are cell header sections and the remaining 48 bytes are user information sections.

The subscriber matching of the ATM cell is performed in the ATM switch, and the multiplexing process of multiplexing the low-speed subscribers divided into several parts in the part of the subscriber matching process to make the high speed or the reverse process is included. .

1 illustrates a system configuration of a multiplexing apparatus for performing the multiplexing process.

As shown in FIG. 1, a general multiplexing apparatus includes a multiplexing board 10, a cell bus 11, and a plurality of subscriber boards 12.

The multiplexing board 10 processes the ATM layer protocol and transmits the processed data to the corresponding subscriber board 12. In general, the multiplexing board has an ATM layer protocol processing capacity of 155Mbps.

The cell bus 11 serves to transmit the cells processed in the multiplexing board to the subscriber board 12. The transfer rate from the cell bus to the subscriber board is 25Mbps and is 16 bits wide.

The subscriber board 12 receives data transmitted from the cell bus 11 and matches the received cells so that the cells can be transmitted to the corresponding subscribers. The plurality of subscriber boards shown in FIG. 1 can each accommodate four subscribers.

2 shows a configuration of a subscriber board.

As shown in FIG. 2, a cell bus matching block 20, a cell memory 21, and four subscriber transmitters 22 are included.

The cell bus matching block 20 transmits and stores the data transmitted from the cell bus 11 to the cell memory 21 and sends the data stored in the cell memory 21 to the corresponding subscriber transmission device 22. Do it. As shown in FIG. 2, the speed of data transmitted from the cell bus 11, the speed of writing data to the cell memory 21 in the cell bus matching block 20, the speed of reading and the width of the data are 25 Mbps / The speed and data width for transferring data from the 16-bit cell bus matching block 20 to the subscriber station 22 is 25 Mbps / 8 bit. Due to the difference in the transmission data width, the cell bus matching block 20 cannot transmit all the data read from the cell memory 21 to the subscriber transmission device 22 at the same clock frequency. shall.

3 illustrates a conventional cell transmission timing structure.

The frame synchronization signal on the cell bus is generated at 28 clock cycles. The cell bus transmits 16 bits, or 2 bytes, of data per clock and 56 bytes of data during one frame. As shown in FIG. 3, cell data is transmitted in a cell bus. That is, one frame is transmitted with a valid cell, a frame sync signal is transmitted, no data is transmitted in the next frame, and the next frame is repeated with the valid cell.

The reason why the effective cell is not transmitted during one frame is that the cell memory 21 of FIG. 2 is divided into a writing time and a reading time. In other words, the data is written to the cell memory 21 in the frame in which the effective cell is transmitted, and the written data is read from the cell memory 21 in the frame in which the valid cell is not transmitted and sent to the subscriber transmission apparatus.

4 shows a cell format transmitted during 28 clocks, which is one frame of the cell bus.

As shown in FIG. 4, a cell transmitted during one frame includes a board ID 41, a link ID 42, a cell header 43, and a payload 44.

The board ID 41 is an ID indicating which of the plurality of subscriber boards 12 connected to the cell bus to the ATM cell processed by the multiplexing board 10 of FIG. 1 and has a size of 1 byte. . The link ID 42 is an ID indicating which of the four subscriber transmission apparatuses in one subscriber board is to be transmitted, and has a size of 1 byte. The subscriber board takes all the cells on the cell bus, analyzes the board ID, stores it in its own memory, and discards it otherwise.

As described above, when all 56-byte cells are transmitted in a cell bus for one frame, and read in the next frame and transmitted to the subscriber transmission device, when the data read from the cell bus matching block 20 to the subscriber transmission device is transmitted. Since the speed is halved, data read at 25Mbps / 16bits from cell memory must store up to 1 cell in the cell bus matching block. Normally, a cell bus matching block consists of a programmable logic array, which requires the use of expensive products to store all of the cells. There is a problem in that the delay of the cell is increased because it is sent to the device.

In the present invention, in order to solve the problems of the prior art as described above, by changing the data transmission method from the cell bus to the subscriber board, to minimize the data space to be stored in the cell bus matching block when transmitting data to the subscriber transmission device The present invention proposes a cell matching method and apparatus for reducing cell delay.

1 shows a system configuration of a multiplexing device,

2 shows a configuration of a subscriber board;

3 illustrates a conventional cell transmission timing structure,

4 illustrates a cell format transmitted during 28 clocks as one frame of a cell bus,

5 illustrates a cell transmission timing structure according to a preferred embodiment of the present invention;

6 illustrates a configuration of a cell bus matching block according to a preferred embodiment of the present invention.

7 is a flow chart of a cell matching method in an ATM switch in accordance with a preferred embodiment of the present invention.

In order to achieve the above object, a cell matching method in an ATM switch system according to the present invention, when one cell unit is designated as 56 clocks when transmitting cell data to a subscriber board through a cell bus, one clock cell is two bytes. Transmitting the data to the cell matching device by repeating the transmission of data and the next clock not transmitting 2 bytes of cell data; Storing the two bytes of cell data received by the cell matching device receiving the transmitted cell data in a cell memory and increasing the write pointer by one; Comparing the write pointer with a read pointer to determine whether there is cell data to be transmitted; Reading the stored two bytes of cell data from the cell matching device using a clock in which cell data is not stored and incrementing the read pointer by one; And transmitting the read cell data to a subscriber transmission device.

In addition, the present invention is characterized in that the transmission of the cell data is determined when the write pointer is larger than the read pointer.

The read cell data is transmitted over two clocks when transmitted to a subscriber transmission device.

In the ATM switch according to the present invention, the cell matching device repeatedly designates one frame unit as 56 clocks, one clock transmits two bytes of cell data, and the next clock does not transmit two bytes of cell data. A cell bus for transmitting data; The memory write unit receives cell data from the cell bus to determine whether the cell data belongs to a corresponding subscriber board, and stores the received 2 bytes of cell data in a cell memory when the cell belongs to a corresponding subscriber board. ; A memory read unit which reads two bytes of cell data stored in the cell memory using a clock in which no data is stored in the cell memory; A memory controller configured to control the use of the cell memory of the memory lead unit and the memory write unit; A memory pointer for determining whether there is cell data to be transmitted by recording a pointer read or stored when reading or storing cell data in the memory read unit and the memory write unit; And a subscriber transmitter matching unit for transmitting the cell data read in the unit of 2 bytes from the memory read unit to the subscriber transmitter.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the cell matching method and apparatus in an asynchronous transmission mode switch according to the present invention.

5 illustrates a cell transmission timing structure according to a preferred embodiment of the present invention.

Conventionally, one frame is composed of 28 clocks, one frame transmits a valid cell, and the next frame repeats the procedure of not transmitting a cell. However, according to a preferred embodiment of the present invention, one frame consists of 56 clocks. One clock sends data and one clock sends no data, sending 56 bytes of cell data for one frame. In FIG. 5, the part indicated by A is a time at which data is transmitted and the part indicated by X is a time at which data is not transmitted.

The subscriber board receiving cell data transmitted in the manner described above at 25 Mbps / 16 bits through the cell bus checks the board ID of the received cell and stores it in the cell memory if the cell corresponds to the cell. According to a preferred embodiment of the present invention, since two bytes are transmitted per clock, two bytes of data are stored in the cell memory.

In the next clock, since no valid cell is transmitted from the cell bus, two bytes of data stored in the cell memory are read and transmitted to the subscriber station. However, since the subscriber transmission device can transmit only one byte of data per clock, the stored two bytes of data are transmitted over two clocks.

In this way, one clock transmits a valid cell and one clock does not transmit. Thus, when a cell bus matching block transmits a cell read to a subscriber station, only two bytes of data are stored internally. There is no overall difference in performance. Therefore, the storage space of the cell bus matching block can be considerably reduced, compared with the conventional cell bus matching block having to store all one cell of 56 bytes. In addition, since data is transmitted directly to the subscriber transmission device in units of 2 bytes, the cell delay can be reduced.

6 illustrates a configuration of a cell bus matching block according to a preferred embodiment of the present invention. Referring to FIG. 6, the configuration and operation of a cell bus matching block for matching data transmitted from the cell bus in the above-described manner and transmitting the same to the subscriber transmitter will be described.

As shown in FIG. 6, the cell bus matching block according to the present invention includes a memory write unit 61, a memory controller 62, a memory pointer 63, a memory read unit 64, and a subscriber. And a transmission device matching section 65.

The memory write unit 61 checks the cell transmitted from the cell bus and stores the transmitted cell in the cell memory when the cell corresponds to the cell. Data is transmitted every one clock on the cell bus, and it is not transmitted. Therefore, if it is confirmed that it is the cell corresponding to itself, the data received at the next clock is stored in the cell memory, and the data is received again at the next clock. Repeat the process to check whether the data corresponds to. If the cell does not correspond to itself, no processing is performed after reception.

According to a preferred embodiment of the present invention, when storing the received data in the cell memory, it is preferable to store data separately for each link (subscriber transmission device) by using the link ID included in the cell.

The memory lead unit 64 reads the data stored in the cell memory by the memory write unit 61 and transmits the data read to the subscriber transmitter matching unit 65. The time for reading data is the time when the memory write unit does not use the memory, that is, the time when the cell is not loaded.

The memory controller 62 controls the operations of the memory write unit 61 and the memory lead unit 64. Since there is only one actual memory and the memory write unit 61 and the memory read unit 64 must use one memory, the operation of the two is controlled by the memory controller 62. That is, the memory controller 62 allows the memory write unit and the memory read unit to use the memory at one clock interval. Therefore, the memory write unit 61 and the memory read unit 64 read or write data through the memory control unit 62.

The memory pointer 63 has a write pointer and a read pointer for each link (subscriber transmission device) to record how much data is currently transmitted to each link (subscriber transmission device) in the cell memory. Since there are four links (subscriber transmission devices) for each subscriber board, there are a total of eight write and read pointers in the memory pointer. When writing data to the cell memory, the write pointer is increased by one, and when reading data, the read pointer is increased by one.

The subscriber transmission device matching unit 65 performs a function of transmitting a cell in accordance with the characteristics of the subscriber transmission device. When data is read in accordance with the cell bus data transmission method, data is read in units of 2 bytes. However, since 2 bytes cannot be transmitted in one clock, 2 bytes of data are transmitted to the subscriber transmitter over two clocks. As an example of a subscriber transmission device matching unit, a utopian type interface is used.

7 is a flowchart illustrating a cell matching method in an ATM switch according to a preferred embodiment of the present invention.

As shown in FIG. 7, one frame unit for transmitting a cell to a subscriber board through a cell bus is designated as 56 clocks (S700). One clock, 56 clocks, transmits the effective cell of 2 bytes, and one clock transmits the cell data to the subscriber board in such a manner that no data is transmitted (S701).

The transmitted valid cell is input to the memory write unit 61 in the subscriber matching block, and the memory write unit 61 determines whether the cell corresponds to the cell. If it is determined that the cell corresponds to the cell, the cell data is stored in the cell memory (S702). In addition, after storing, the location stored in the cell memory is recorded in the write pointer for each link, and one write pointer is added.

To determine whether to transmit the data stored in the cell memory to the subscriber transmission device, the value of the memory pointer 63 is compared (S703). As described above, since the write pointer storing the data and the read pointer reading the data are recorded for each link, if the read pointer and the write pointer are the same, there is no data to be transmitted. If the write pointer is larger than the read pointer, the transfer is performed. Determine that there is data to be done

If it is determined that there is data to be transmitted (S704), the current state of the subscriber transmission device matching unit is grasped to determine whether the current data can be sent or whether the current data is difficult to be transmitted further. S705).

In a situation where data can be transferred, the memory read unit 64 reads two bytes of data from the cell memory during the clock in which the memory write unit 61 does not write the cell data in the cell memory (S706). When the data is read, the read pointer of the memory pointer is increased by one.

Since the subscriber transmission device can accommodate only 8 bits during one clock, the data read by the subscriber transmission device matching unit 65 is transmitted to the corresponding subscriber transmission device over two clocks (S707).

As described above, according to the cell matching method and apparatus in the asynchronous transfer mode switch according to the present invention, the cell data is stored in the cell memory in unit of two bytes by changing the transfer method in the cell bus and then through the cell matching block. Since the cell matching block only needs to store 2 bytes, the cell matching block can reduce the storage space considerably compared to the case of storing a conventional 56-byte cell in the cell matching block. In addition, there is a delay in the cell because all cells of 56 bytes are received and stored in one frame and the cells are transmitted in the next frame. However, since cells received in 2-byte units are transmitted at the next clock, a problem occurs when the cell is transmitted. This has the advantage of greatly reducing the delay.

Claims (6)

When transferring cell data to the subscriber board through the cell bus, one clock unit is designated as 56 clocks so that one clock transmits two bytes of cell data and the next clock does not transmit two bytes of cell data. Transmitting cell data; Storing the two bytes of cell data received by the cell matching device receiving the transmitted cell data in a cell memory and increasing the write pointer by one; Comparing the write pointer with a read pointer to determine whether there is cell data to be transmitted; Reading the stored two bytes of cell data from the cell matching device using a clock in which cell data is not stored and incrementing the read pointer by one; And And transmitting the read cell data to a subscriber transmission device. The method of claim 1, And determine the transmission of cell data when the write pointer is larger than the read pointer. The method of claim 1, And transmitting the read cell data over two clocks when transmitting the read cell data to a subscriber station. The method of claim 1, When storing the cell data, each cell data is classified and stored for each subscriber transmission device to be transmitted. A cell bus that repeatedly transmits data by designating one frame unit as 56 clocks, one clock transmitting two bytes of cell data, and the next clock not transmitting two bytes of cell data; The memory write unit receives cell data from the cell bus to determine whether the cell data belongs to a corresponding subscriber board, and stores the received 2 bytes of cell data in a cell memory when the cell belongs to a corresponding subscriber board. ; A memory read unit which reads two bytes of cell data stored in the cell memory using a clock in which no data is stored in the cell memory; A memory controller configured to control the use of the cell memory of the memory lead unit and the memory write unit; A memory pointer for determining whether there is cell data to be transmitted by recording a pointer read or stored when reading or storing cell data in the memory read unit and the memory write unit; And And a subscriber station matching unit for transmitting cell data read in units of two bytes from the memory read unit to a subscriber station. The method of claim 5, Cell data storage in the memory write unit and pointer recording in the memory pointer are stored or recorded separately for each subscriber transmission device to which a corresponding cell is to be transmitted.