KR970002722B1 - Sar receiver processor of atm - Google Patents

Abstract

An SAR transmission process device for the ATM communication type where embodies the ATM adaptive layer(AAL) 3/4 segment and reassembly sublayer(SAR) to the hardware. The total length of the data where is stored in the FIFO, makes a multiple of 48 bytes. The said process device consist of a message length operation part, a counter and controller, a FIFO controller, a pad generating means, a selection means where selects the FIFO data, the pad or the trailer.

Description

SAR receiver processing system of ATM communication system

1 is a block diagram showing a SAR receiving processing apparatus according to the present invention;

2 is a view illustrating a SAR receiving processing apparatus according to the present invention.

(a) shows a data flow structure of an AAL layer;

(b) shows a format of SAR-PDU data;

3 illustrates the structure of a typical ATM cell.

(a) shows the structure of the entire ATM cell;

(b) illustrates an ATM cell header structure of a user network interface (UNI),

(c) shows the ATM cell header structure of the network node interface (NNI).

* Explanation of symbols for main parts of the drawings

1,3: FIFO 2: SAR receiver

21: flip-flop 22: counter and control unit

23: CRC & FIFO lead circuit 24: SAR header processing unit

25: SAR trailer processing unit 26: Assembly completion signal generation unit

27: error processing unit 28: length calculation circuit

The present invention connects an ATM layer and a higher user service layer in an asynchronous transfer mode (ATM) communication method, matches user service information with an ATM cell format, and processes an ATM error (AAL: ATM Adaptation Layer). In particular, the 48-byte cell data received from the ATM layer separates the SAR header and the SAR trailer, checks for errors, and reassembles and reassembles the data to the convergence (CS) Convergence Sublayer (CS) sublayer. SAR: Sagmentation And Resasembly Sublayer).

Recently, as the means of communication has been rapidly digitalized and the development of optical communication enables transmission of a wide band, broadband ISDN (Broadband Integrated Services Digital Network) has emerged to meet various user's service needs.

That is, B-ISDN is a video telephony service from narrowband services such as remote meter reading, data terminal, telephone, facsimile, etc. It is designed to handle and deliver broadband services such as video conferencing, high-speed data transmission, and video signal transmission in common, and is implemented based on the asynchronous transmission mode (ATM) communication method.

The ATM communication method is similar to the conventional packet communication method in that ATM cells are transmitted by cell unit by Asynchronous Time Division Multiplexing (ATDM). It handles even the signal of the constant bit rate and is standardized by the International Organization for Standardization to be used not only in local area networks but also in huge public networks.

This ATM communication method is based on ATM cells as shown in (a) to (c) of FIG. 3, where a user's long message is divided into ATM cells and transmitted, and the received ATM cells are again one message. Is reassembled and forwarded to the parent user.

That is, as shown in (a) of FIG. 3, an ATM cell is divided into a header section of 5 bytes (or octets) and a user information section of 48 bytes, and the header of 5 bytes is shown in FIGS. As shown in c), the header structure is divided into a header structure at the user network interface (UNI) and a header structure at the network node interface (NNI), and a header structure at the user network interface (UNI). The first byte consists of 4 bits of Generic Flow Control (GFC) and 4 bits of Virtual Path Identifier (VPI), and the second byte consists of 4 bits of Virtual Path Identifier (VPI). ) And a 4-bit Virtual Channel Identifier (VCI), the third byte consists of an 8-bit Virtual Channel Identifier (VCI), and the fourth byte is a 4-bit Virtual Channel Identifier (VCI). VCI), 3-bit payload type (PT) and 1-bit cell abandonment ranking (CLP) : Cell Loss Priority, and the fifth byte is composed of 8-bit header error control (HEC).

Also, looking at the header structure of the network node interface (NNI) as shown in FIG. 3C, the general flow control (GFC) in the first byte of the user network interface (UNI) described above is a virtual path identification number. It can be seen that it is the same as the header structure of NNI except that it is used as (VPI).

This ATM communication method has a hierarchical structure as shown in [Table 1] and has standardized standards for each layer.

TABLE 1

"""""""" ^{10 9 5 4}

&

&

"" ""

Claims (1)

A SAR receiving processing apparatus according to AAL 3/4 protocol of ATM communication system, comprising: a counter and a controller for receiving a delayed SAR-UNITDATA-invoke signal to count a predetermined count value and generating CRC and FIFO control signals (22); Receives the SAR-UNITDATA-invoke signal, sequentially reads segment data according to the counter and control signals of the controller 22, CRC processes the data in 48-byte units, detects and corrects errors, and delivers data. A CRC and FIFO lead circuit 23; A SAR header processor (24) for checking whether an error has occurred after separating the SAR header from 48 bytes of data according to the counter and the control signal (s-h) of the control unit (22); A SAR trailer processing unit (25) for checking whether an error has occurred after separating the SAR trailer from 48 bytes of data according to the counter and the control signal (s-t) of the control unit (22); The counter and the control unit 22 completes counting for one segment and inputs the generated count complete signal and the segment type data (rcv-st) included in the header of the received segment to complete assembling one message. An assembly completion signal generator 26 generating a CPCS-UNITDATA-invoke signal; After inputting an error detection signal from the SAR header processing unit 24, the SAR trailer processing unit 25, the CRC and the FIFO lead circuit 23, a user abort signal or protocol abort (SAR) is assembled. An error processing unit 27 generating a -U-Abort) signal; And a length calculation circuit 28 for inputting the length indication (LI) data from the SAR trailer processing unit 25 to calculate the total length of the message, and having a length calculation circuit 28 for the two-byte SAR header in the 48-byte segment received from the lower ATM layer. SAR communication system of the ATM communication method characterized in that the two-byte SAR trailer to check the error, and to assemble each of the relevant segments to restore a single message and to upload to the CPCS layer.