JPH06104913A - Sequence number reception controller for informaiton cell in atm and its method - Google Patents

Abstract

PURPOSE:To make the sequence number reception processing efficient by revising a sequence number to be stored when a control cell is given during reception of an information cell into a sequence number of a first information cell received after the control cell. CONSTITUTION:When a received information cell is a cell received just after the reception of the control cell from a control cell detection circuit 35, the revision processing of the sequence number of the information cell received precedingly is finished and down-loaded to a counter. Thus, the number processing of the information cell is restarted from a sequence number of the first information cell received afterward. Furthermore, when the information cells are continuously received not through a control cell, the number of the information cell is compared with the sequence number whose reception is expected and stored in the counter and when they are coincident, the cell number is revised into the sequence number of the information cell whose reception is expected. Thus, the deterioration in the transmission efficiency and processing efficiency due to the use of plural same control cells is prevented and the reception processing of the sequence number is made efficient.

Description

Detailed Description of the Invention

[0001]

The present invention relates to an ATM (Asynchronous Trunk).
Ansfer Mode) Regarding reception control of sequence number (SN) of information cell in communication, particularly reception control device of a sequence number assigned to a plurality of information cells into which one data is divided and a control cell used for transmission control thereof. And its method.

[0002]

2. Description of the Related Art In recent years, a broadband ISDN has been used by an ATM network.
Research to realize (B-ISDN) has been actively conducted, in which an electrical signal interface HIPPI (High Performa) that performs high-speed transfer at 800 Mbps is provided.
A large amount of data is being transferred mainly between supercomputers and information terminals using the nce Parallel Interface). In the HIPPI, one information unit is a packet,
The packet is divided into fixed-length units and called a burst. The burst data is converted into ATM cells in the terminal adapter (TA) on the transmitting side and transmitted to the TA on the receiving side via the ATM switching network.
On the receiving side, the original HIPP is converted by the reverse conversion.
I data is restored.

FIG. 6 shows an HI provided by an ATM network.
1 shows an example of a system configuration of a communication form using a PPI interface. In FIG. 6, the ATM network 40 has H
IPPI interface terminal adapter (HI
A plurality of PPI-TAs 41 (# 1 to # 3, etc.) are connected, and a terminal (TE) 42 is connected to each HIPPI-TA 41. Further, the TA 44 for another interface is connected to the ATM network 40, and the TA 44
A TE 45 is connected to.

FIG. 7 shows the frame structure of the HIPPI protocol.
It is a success. In the HIPPI protocol, as shown in FIG.
Received from the host device (computer, TE, etc.) as shown
A chunk of data is called a packet, and that packet
Has a maximum length of 4G (giga = 10 ⁹) It's a byte. This
KET is the HIPPI interface at the terminal 42.
In the mechanism, it is called a burst shown in FIG.
Is divided into fixed length units of 1K (kilobytes)
(Data bus, control bus, address bus, etc.)
High-speed transfer is performed with the terminal adapter 41.
It The terminal adapter 41 sends this burst to the ATM.
Converted to a protocol and transmitted through the ATM network 40
It

FIG. 8 shows an example of the frame structure of the burst and ATM protocol. Each burst shown in FIG. 8A is a PDU (Packet Data Uni) of level 2 (second layer of the OSI standard layer model recommended by ISO: data link layer).
t) and transmitted. As the configuration method of this PDU, SMDS (Switched Megabi) recommended in the United States is used.
A cell configuration using a sublayer of SAR (Segmentation And Reassembly) defined as a Type 4 format of t Data Service is used. The configuration is shown in FIG. This SAR-PDU cell (48 bytes or octets in total) has a 2-byte header, 4
It is composed of a 4-byte payload (a part of burst data to be transmitted) and a 2-byte trailer.

The HIPPI-TA 41 of FIG. 6 converts each burst forming a packet sent from the connected upper device TE 42 into a SAR-PDU cell,
An ATM cell header (5 bytes) is added to generate an ATM cell (53 bytes in total) shown in FIG. 8C and transmitted to the ATM network 40. Further, the HIPPI-TA 41 on the receiving side of the ATM network 40 receives this, and then receives it from the ATM cell ((C) in FIG. 8) to the SAR-PDU ((B) in FIG. 8).
, And each SAR-PDU is decomposed to reproduce the burst ((A) of FIG. 8), and further the packet ((A) of FIG. 7) is reproduced and passed to the TE 42 which is a higher-level device.

FIG. 9 shows the SAR-PD shown in FIG.
The format of U is shown. This header is 2
Information indicating a bit segment type (ST), a 4-bit sequence number (SN), and a multiple identifier (MI
D). The segment type ST represents an attribute of each cell such as a head cell (BOM) and an intermediate cell (COM), and a sequence number SN is assigned a modulo 16 cyclic number from 0H to FH. And the multiple identifier MI
D is for identifying cells of a plurality of channels multiplexed on the same virtual channel identifier (VCI). Next, the trailer indicates the effective length of the data contained in the payload by the 6-bit LEN (Length), and the remaining 10
The bit is a CRC for error checking.

FIG. 10 shows the AT shown in FIG. 8C.
An example of transmission of information cells and control cells of M-cell configuration is schematically illustrated, with the sequence number SN below each cell.
It is shown. The sequence number SN is a number assigned to the SN portion of FIG. 9, and the information cell and the control cell are distinguished from each other by the information portion (SAR-PAYLOA) shown in FIG.
It is determined by the bit pattern assigned to the first 8 bits of D). For example, the information cell is 00H, and FIG.
REQ-ON of control cell of 0 is 80H, REQ-OFF
Is 40H or the like.

[0009]

However, the ATM
In communication, cells may be forcibly discarded at the time of line congestion, and cell loss may occur due to deterioration of communication line conditions. In this case, if the control cell is discarded or the cell is dropped as shown in FIG. 10, the division of the information cell becomes unclear, and the communication procedure itself is abnormal. As a measure against such a case, conventionally, in consideration of the quality of the ATM network, a plurality of the same control cells are continuously transmitted on the transmitting side so that the above problem does not occur even if the cell is discarded or dropped. It was

However, in that case, there is a problem that the processing efficiency is lowered because all the plurality of the same control cells are processed although the processing of one control cell is originally required. Further, for that purpose, the number of transmissions of the same control cell is preliminarily agreed between the transmitting side and the receiving side, and the receiving side sets 1
Only one control cell is processed, the sequence number of the information cell expected to be received next is counted up by the number of control cells including the remaining control cells, and the subsequent information cells are normally received. The method etc. were taken. However, this method also complicates the process at the time of cell reception as compared with the conventional method, and changes the number of control cells to be transmitted individually for each line or communication in consideration of transmission efficiency, line state, etc. In this case, it is necessary to make the above arrangement between the transmitting side and the receiving side, and there is a problem particularly in the case of transmitting data via an unspecified line such as a public line.

Therefore, in view of the above problems, an object of the present invention is to reduce the number of cells to be processed to one when receiving a plurality of the same control cells described above, and further, it is necessary to make an agreement between the transmission and reception. By eliminating the above, the problems such as the decrease in the processing efficiency and the complication of the processing content described above are to be solved. Further, at that time, it is intended to realize them by a simple apparatus and method using the conventional method as much as possible.

[0012]

According to the present invention, the sequence number processing of the information cells is performed for each reception of the control cells. That is, upon reception of the control cell, the sequence number processing of the information cells received up to that point is temporarily terminated and only the first one of the plurality of identical control cells described above is processed. When a new information cell is received immediately after the reception of the plurality of identical control cells, the sequence number of the information cell is regarded as correct and the sequence number processing is restarted from that number.

As shown in FIG. 1, an apparatus for receiving and controlling a sequence number of an information cell in an ATM comprises a sequence number holding means 2 for holding a sequence number (SN) of a received information cell, the information. The data holding means 3 for temporarily holding the cell, the control cell detecting means 1 for detecting the control cell used for communication control of the information cell, and the reception sequence number from the sequence number holding means 2 are received. The sequence number of the information cell first received after performing confirmation processing to confirm that it is an expected number or when receiving the control cell detection signal from the control cell detection means 1 is the number expected to be received. And the sequence number processing means 4 for continuing the confirmation processing thereafter, and the sequence number processing means 4
An information cell sequence number reception control device is provided which comprises data processing means 5 for performing a predetermined process on the information cell held in the data holding means 3 in accordance with the confirmation processing and interfacing to the outside.

Further, according to the present invention, when the control cell used for communication control of the information cell is received, the predetermined sequence number processing of the information cell received before that is ended,
A sequence number reception control method of an information cell is provided, which restarts a predetermined sequence number processing of the received information cell from the sequence number of the first information cell received thereafter.

[0015]

The data holding means 3 stores information cells in, for example, a FIFO.
Temporary buffering is done by memory etc. The sequence number holding means 2 latches the sequence number (SN) included in the header portion of FIG. 9 at a predetermined timing, for example, and the control cell detection means 1 controls the control cell included at the beginning of the payload portion of FIG. 9 described above. The control cell is detected by the identification pattern. The sequence number processing means 4
The sequence number expected to be received and the sequence number of the information cell received from the sequence number holding means 2 are compared and checked, and if they coincide with each other, the sequence number is incremented by +1 for each reception. , Updates the sequence number for confirmation of normal reception of the next information cell. If the comparison results do not match, it is determined that an information cell is missing, and the data processing means 5 to be described later is instructed to perform a predetermined process.

When a control cell detection signal is given from the control cell detection means 1 during reception of an information cell, the sequence number processing means 4 stores the sequence number held by itself as the first information cell received after the control cell. Replace with the sequence number of. That is, the sequence number of the first information cell is regarded as correct, and the above processing is repeated thereafter. The data processing means 5 is the data holding means 3
Predetermined conversion may be performed on the information cells buffered in, for example, header removal or the like, and an interface function with the output side may be executed. Further, when the sequence number processing means 4 gives a reception error signal such as the drop of the information cell, a predetermined process such as cell discard may be performed.

[0017]

FIG. 2 is a block diagram schematically showing an example in which the sequence number receiving apparatus for information cells according to the present invention is applied to an ATM network. In FIG. 2, the sender HIPP
The I interface circuit 11 receives data and the like from the terminal TE, and the SAR header circuit 13 divides the received data into a predetermined length and adds the SAR header and trailer portion to it. At that time, a sequence number of modulo 16 is added from the sequence number generator 14. The sequence number generator 14 may be included in a part of the SAR header circuit 13 (enclosed by a dotted line 12). The ATM header circuit 15 further adds an ATM header to the data to generate an ATM cell, and the ATM cell is converted into, for example, an optical signal by the B-ISDN interface circuit 16 and output to the ATM network. The output signal is ATM
The ATM switch 17 in the network makes a switching connection to the intended receiving side.

On the receiving side, the reverse process to the above is performed, and B
-The ISDN interface circuit 18 performs optical-electrical conversion of the ATM signal, the ATM header circuit 19 checks and removes the received ATM header portion, and the SAR header circuit 21 checks the SAR header and trailer portion. And removing, and combining the divided data. At this time, the sequence number control circuit 22 controls the reception of the sequence number according to the present invention. The sequence number control circuit 22 uses the SAR
It may be included in a part of the header circuit 21 (2 surrounded by a dotted line).
0). The data is the HIPPI interface circuit 2
3 to the receiving terminal TE.

FIG. 3 shows an example of the configuration of the SAR header circuit 21 and the sequence number control circuit 22 of FIG. As for the relationship between the present invention of FIG. 3 and FIG.
The input buffer 31, the sequence number holding circuit 34, and the control cell detection circuit 35 correspond to the data holding means 3, the sequence number holding means 2, and the control cell detection means 1 of FIG. 1, respectively. Further, the microprocessor 36 of FIG. 3 is connected to the sequence number processing means 4 of FIG.
The R header processing circuit 32 and the output buffer 33 correspond to the data processing means of FIG.

In the example of FIG. 3, the input buffer 31 and the output buffer 33 are composed of a FIFO memory or the like, and the sequence holding circuit 34 and the control cell detection circuit 35 latch a predetermined portion of the input data at a predetermined timing or need it. Then, it consists of a circuit etc. for decoding it. The microprocessor 36 has a built-in ROM such as a one-chip control microprocessor in which a control program is written, a RAM for holding data, and a hardware counter. The SAR header processing circuit 32 includes the above-mentioned SAR header, dedicated hardware for trailer processing, a microprocessor circuit, and the like.

FIG. 4 is a flow chart showing an embodiment of the information cell receiving process of the present invention executed by the microprocessor 36. In FIG. 4, step S1
Then, it is determined whether or not the received information cell has been received immediately after the control cell detection signal from the control cell detection circuit 35. If it is received immediately after receiving the control cell, the updating process of the sequence number of the information cell, which has been performed before the receiving of the control cell, is terminated in step S2, and the information cell received immediately after receiving the control cell is The sequence number is considered correct and is downloaded to a built-in counter which holds the sequence number of the information cell, for example.

Therefore, for information cells received thereafter, the so-called later-described +1 increment processing of the counter is restarted from this sequence number. In this case, only the first cell is processed for the control cell, and the above-described conventional process for increasing the counter by the number of control cells is unnecessary. The continuity of the entire sequence number including the information cell and the control cell is monitored at another location, and the cell drop of the control cell or the like can be detected there.

When it is determined in step S1 that the information cells are continuously received without passing through the control cell, in step S3, for example, the sequence number expected to be received held in the counter and the received information cell are received. The sequence number of the information cell that has been stored is compared. If they match, the counter is incremented by +1 in step S4 and updated to the sequence number of the information cell expected to be received next. On the contrary, if they do not match, step S5
The information cell drop is instructed externally by.

FIG. 5 shows an example in which the number of control cells inserted between information cells is changed depending on the state of the communication line and the like. FIG. 5A shows a case where the line condition is good and the cell transmission efficiency is utilized to the maximum,
On the contrary, FIG. 5C shows a case where the line condition is bad and the cell drop of the control cell is prevented even if the transmission efficiency of the cell is sacrificed. Further, FIG. 5 (B) shows an intermediate case.

According to the above-mentioned conventional method, FIG.
From FIG. 5 to FIG. 5C, the number of processing of unnecessary control cells increases, or the processing content such as arrangement of skipping sequence numbers of information cells due to the number of control cells becomes complicated, but according to the present invention. For example, in any of FIGS. 5A to 5C, the number of processed control cells is one (control cell with SN = 1), and it is necessary to negotiate the number of control cells as in the conventional case. There is no. That is, by receiving the first information cell after receiving the control cell, the sequence number processing of the information cell is restarted from the sequence number SN = 2 in (A) of FIG. 5, and from the sequence number SN = 3 in (B) of FIG. The sequence number processing of the information cell is restarted, and in FIG. 5C, the sequence number processing of the information cell is restarted from the sequence number SN = 4. At that time, all that is necessary is an operation of resetting the sequence number of the information cell immediately after the reception of the final control cell, for example, in the counter as a sequence number for starting a new reception.

[0026]

As described above, according to the present invention, even when a plurality of identical control cells are received, the number of cells to be processed is only one. Processing complexity is avoided. Therefore, it is possible to prevent the cell transmission efficiency and processing efficiency from decreasing and the processing content to be complicated by using a plurality of the same control cells, and it is possible to individually and optimally set them for each line. . Further, according to the present invention, the above advantages can be provided by a simple apparatus and method using the conventional method as much as possible.

[Brief description of drawings]

FIG. 1 is a block diagram showing a basic configuration of an information cell sequence number reception control apparatus according to the present invention.

FIG. 2 is a diagram showing an example in which a sequence number reception control device of an information cell according to the present invention is applied to an ATM network.

FIG. 3 is a block diagram showing an embodiment of an information cell sequence number reception control apparatus according to the present invention.

FIG. 4 is a control flow diagram showing an example of reception control processing of an information cell according to the present invention.

FIG. 5 is a diagram schematically showing an example of information cell transmission including a plurality of control cells.

FIG. 6 is a diagram schematically showing an example of a communication mode in which HIPPI is applied to an ATM network.

FIG. 7 is a diagram showing a frame structure of a HIPPI protocol.

FIG. 8 is a diagram showing a frame structure between a burst and an ATM cell.

FIG. 9 is a diagram showing a format configuration of SAR-PDU.

FIG. 10 is a diagram schematically showing an example of ATM cell transmission.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Control cell detection means 2 ... Sequence number holding means 3 ... Data holding means 4 ... Sequence number processing means 5 ... Data processing means TA ... Terminal adapter TE ... Terminal device

Claims (3)

[Claims] 1. An apparatus for receiving and controlling a sequence number of an information cell in ATM comprises a sequence number holding means (2) for holding a sequence number (SN) of the received information cell, and the information cell is temporarily stored. Data holding means (3) for holding information, control cell detecting means (1) for detecting control cells used for communication control of information cells, etc., reception sequence number from the sequence number holding means (2) Is the number expected to be received, or when the control cell detection means (1) receives the detection signal of the control cell, the sequence number of the information cell received first is then received. Of the sequence number processing means (4) for continuing the confirmation processing after that, and confirming the sequence number processing means (4). Data processing means (5) for performing predetermined processing on the information cells held in the data holding means (3) according to the processing and interfacing to the outside.
A sequence number reception control device for an information cell, comprising: 2. A method of receiving and controlling a sequence number of an information cell in ATM is a predetermined sequence number processing of an information cell previously received when a control cell used for communication control of the information cell is received. Is terminated and the predetermined sequence number processing of the received information cell is restarted from the sequence number of the first information cell received after that. 3. A method of receiving and controlling a sequence number of an information cell in ATM comprises: determining whether the received information cell is an information cell immediately after receiving a control cell used for communication control of the information cell or the like. 1 step, if the information cell is an information cell immediately after receiving the control cell, a second step of using the sequence number of the information cell as a sequence number of the information cell expected to be received, the information cell Is other than the information cell immediately after receiving the control cell, the third step of comparing the sequence number of the information cell expected to be received with the sequence number of the received information cell, and the comparison is matched. In case of using the sequence number of the received information cell, the sequence number is incremented by +1 for receiving the next expected information cell. Information cell, which comprises a fourth step of decrementing, and a fifth step of instructing to drop an information cell if the comparison does not match, and these steps are repeatedly performed each time an information cell is received. Sequence number reception control method.