KR0129179B1 - A circuit for decoding pdu in sscop sublayer - Google Patents

Abstract

A PDU interpreting circuit in SSCOP auxiliary layer is provided, which includes a down counter(10) for down-counting accoring to certain message receiving signal to output control signal; a FIFO reading controlling unit(14) for reading message stored in received AAL FIFO(12); a FIFO writing controlling unit(16) for write data read by the FIFO reading controlling unit(14) to receive queue FIFO(18) according to control signal of the down counter(10); a plurality of 32 bit registers(20, 22, 24) for reading certain word from the FIFO reading control unit(14); a demultiplexer(26) for reading word stored in each register(20, 23, 24) to store read word to state variable storing unit(28).

Description

PDU Analysis Circuit in SSCOP Sublayer

1 is a diagram showing the structure of a signal protocol including a B-ISDN signal adaptation layer.

FIG. 2 is a diagram illustrating a PDU mapping structure of the signal adaptation layer shown in FIG.

3 is a flowchart illustrating signal link activation, deactivation, and recovery of the signal adaptation layer.

4 is a block diagram showing a PDU generation circuit of the SSCOP sublayer according to the present invention.

* Explanation of symbols for main parts of the drawings

10: down counting unit 12: receiving AAL FIFO

14: FIFO read circuit 16: FIFO read control

18: Receive queue FIFO 20: First register

22: second register 24: third register

26: DEMUX 28: State Variable

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit for implementing a signal protocol used in B-ISDN, which uses an Asynchronous Transfer Mode (ATM) communication method as a basic transmission means, and in particular, SSCOP (Service Specific Oriented) of a signal adaptation layer (SALL). Protocol ol) This is a PDU analysis circuit that separates and processes the contents of a control field into messages transmitted from a lower layer in a sublayer. Recently, as the means of communication is rapidly digitized and the development of optical communication enables the transmission of a wide band, broadband ISDN (B-ISDN) has been developed as a next-generation communication network to meet various user needs. In this B-ISDN, not only the existing narrowband services such as remote metering, data terminal, telephone, and facsimile but also broadband services such as video telephony, video conferencing, high-speed data transmission, and video signal transmission, etc. It is implemented based on ATM communication method which is asynchronous delivery mode to accommodate all regardless of speed.

Here, the AMT communication method is a method that communicates by asynchronous time division multiplexing (ATDM) of ATM cells having a total length of 53 bytes composed of a 5 byte header section and a 48-byte user information section. It is similar to the conventional packet communication method in that it is transmitted in the ATM, but ATM communication method handles signals of real time and identity rate, and is different in that it can be used not only in local area network but also huge notary network.

In the ATM communication method, the signal protocol structure is shown in FIG. 1. The functions of each of these layers are shown in Table 1.

As shown in Table 1, the structure of the ATM protocol is divided into vertical structures such as a physical layer, an ATM layer, a Signaling ATM Adaptation Layer (SAAL), and a higher protocol layer. Is divided into a common part layer (CP AAL) and a service specific convergence sublayer (SSCS), and the service specific sublayer is a SSCF (Service Specific Co-ordination Function), SSCOP ( Service Specific Connection Oriente d Protocol).

On the other hand, each of these layers has a mapping structure, as shown in Figure 2, SSCF adds 5 octets of information to the data received from the upper layer to pass to the SSCOP layer, an integer multiple of 4 octets in the SSCOP layer The PAD and predetermined trailer information are added to the CPCS layer for alignment, and the CPCS layer adds the PAD and the predetermined trailer to the SAR layer to make an integer multiple of 48 octets. The SAR sublayer informs the end of the SAR-PDU to enable the preservation of the SAR-PDU, to process the congestion information, and to process the loss priority information, and to separate the data received from the CPCS into 48 octets. The ATM layer transfers the transferred data by adding a predetermined header of 5 bits in length.

SSCOP is a function of signal adaptation layer that is used to transfer variable length service data units (SDUs) between users, and has the function of recovering lost or damaged SDUs. Receives the signal data transmission request from the user or layer 3 of the signal adaptation layer and transmits it to the same layer transparently and without errors. This corresponds to the existing layer 2, and corresponds to the user network interface (UNI) and the network node interface ( NNI (Network Interface) can be used in common, and its functions are shown in Table 2 below.

In the SSCOP sublayer, which performs the functions as shown in Table 2, the signal flow of the signal adaptation layer shown in FIG. 3 is shown. When the request for deactivation and recovery is transmitted to the SSCF layer, the SSCF layer sends predetermined primitives to the SSCOP, and the SSCOP creates a message corresponding to the primitive and delivers the message to the CPCS layer, but the CPCS-UNITDATA- Two signals are used, invoke and CPCS-UNIT-signal. In this case, a message transmitted or received at the SSCOP sublayer, that is, an SSCOP PDU, has a pad length of 0 to 3 octets and a predetermined length of 4 octets to align the data transmitted from the SSCF by an integer multiple of 4 octets, as shown in FIG. The control field is added, and the maximum possible length is 65528 octets minus 8 octets of CPCS trailers from 65536 octets, which is the maximum possible length of CPCS PDUs. The maximum possible length of. The four octet control field consists of a 2-bit pad length, a 2-bit unused portion, a 4-bit PDU type, and a 3-octet length PDU variable.These control fields specify the nature of the message delivered and the SSCOP layer. It will contain a variety of information to perform the function.

Accordingly, the present invention separates the control field including various information required in the SSCOP sublayer from the message transmitted from the lower layer and the data to be transmitted to the upper layer and stores the data according to the SSCOP sublayer so as to perform a predetermined processing operation. The purpose is to provide a PDU analysis circuit at the layer. The circuit of the present invention for achieving the above object, in the SSCOP layer that receives the signal data transfer request from the SSCF layer and transparently and transparently transfers them to the same layer, down counting and control by a predetermined message arrival signal A down counter configured to output a signal; A FIFO read control unit for reading a message stored in the received ALL FIFO by the control signal of the down counter; A FIFO write control unit which enables the data read by the FIFO read control unit to be written to a reception queue FIFO by the control signal of the down counter; A plurality of 32-bit registers for reading a predetermined word from the FIFO read control unit; And a PDU analysis circuit configured to demux the predetermined state variables by reading the words stored in the registers and storing them in the state variable storage unit. Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. 4 is a block diagram of a PDU analysis circuit according to the present invention, which includes a down counter 10 for counting down a message arrival signal and outputting a control signal; A FIFO read control unit 14 for reading a message stored in the received AAL FIFO 12 according to the control signal of the down counter 10; A FIFO write control unit (16) which enables the data read by the FIFO read control unit (14) to be written to the reception queue FIFO (18) by the control signal of the down counter (10); A plurality of 32-bit registers (20, 22, 24) for reading a predetermined word from the FIFO read control unit (14); The demux 26 reads words stored in the registers 20, 22, and 24, and demuxes predetermined state variables to be stored in the state variable storage unit 28. The SSCOP processing circuit stores and manages certain state variables, and thus controls the operation of the entire circuit. In addition, the SSCOP processing circuit maps these state variables to control fields and transmits them during the exchange of messages between peers. It is performing a function. Therefore, the state control unit for maintaining the state of the entire circuit of the SSCOP should change and store the state variable by interpreting the user's information and messages received from the peer layer, the present invention is interpreted the received message, that is, PDU The state variable and PDU type transmitted to the control field are analyzed.

The state variables used in the SSCOP layer are shown in Table 3 below.

Each of the state variables in Table 3 includes various types of information for control transmission between linked entities. Each of these state variables is mapped to a predetermined PDU and transmitted to the other party as needed. The down counter 10 receives the word length of the received message and sets the initial value and down counts at the same time, thereby controlling the entire circuit. The FIFO read control unit 14 reads a message received from the receiving AAL FIFO 12, that is, a PDU by the control signal of the down counter 10. The FIFO recording controller 16 controls the reception queue buffer 18 to store data to be transmitted to the upper layer included in the PDU, and is operated by the control of the down counter 10. The registers 20, 22, and 24 store the control fields of the received message in word units. The control fields are composed of different configurations and lengths of the control fields according to the types of each PDU. The control information required for transmission and reception is included. The control fields added to the trailing end of the PDU by the output of the down count 10 are sequentially read and stored one world by one register 20, 22, and 24. As a result, the number of registers used may also be added or subtracted.

The words stored in the registers 20, 22, and 24 are interpreted in word units by the DEMUX 26, and the PSC is analyzed by analyzing various state variables and PDUs included in various control fields added to the PDU. Output to the state variable storage unit 18 in charge of the control function in the circuit

The operation of the present invention configured as described above is as follows. If a predetermined PDU is stored in the received AAL FIFO, and the length signal is input together with the message arrival signal from the lower layer, the down counter 10 sets an initial value according to the input length signal and down counts.

During the down count operation, the FIFO read control unit 14 reads the received PDU from the receiving AAL FIFO 12 in word units and outputs the word unit. In this case, the output word is divided into a data field and a control field, and is output. The data field is first output to the reception queue FIFO 18 and then the control field is output to the registers 20, 22, and 24. do. On the other hand, the FIFO write control unit 16 operated by the output signal of the down counter 10 controls the reception queue FIFO 18 and the data field read by the FIFO read control unit 14 from the AAL FIFO 14. This allows you to write, but only while the message being processed is a data field.

After the data field of the message received by the above process is stored in the reception queue FIFO 18, processing of the control field is as follows. If the processed message is a control field, the FIFO read control unit 14 sequentially stores the words of the read control field in the first register 20, the second register 22, and the third register 24, respectively. The stored words are again divided into respective PDU variables including predetermined control information in the demux 26 and output to the state variable storage unit 28.

As described above, the PDU analysis circuit of the present invention separates only the control field including various control information transmitted and received in the SSCOP layer from the message, interprets a predetermined state variable therefrom, and delivers it to the SSCOP processing circuit. By using a down counter and a large number of registers, it enables high speed processing.

Claims (1)

A down counter 10 which counts down by a predetermined message arrival signal and outputs a control signal; A FIFO read control unit 14 for reading a message stored in the received AAL FIFO 12 according to the control signal of the down counter 10; A FIFO write control unit (16) which enables the data read by the FIFO read control unit (14) to be written to the reception queue FIFO (18) by the control signal of the down counter (10); A plurality of 32-bit registers (20, 22, 24) for reading a predetermined word from the FIFO read control unit (14); And a demux (26) configured to read the words stored in the registers (20, 22, and 24), and demux predetermined state variables to store them in the state variable storage unit (28).