KR0129185B1 - A circuit for generating pdu in sscop sublayer - Google Patents

Abstract

a counter(10) which performs down-counting by inputting a start signal, with its initial value set to 4; a first and second register(14,16) of 32 bit length storing sequence number(N(S)) temporarily inputted from a state variable storing part(12); a third register(18) of 32 bit length storing maximum permissible reception state number(N(MR)) temporarily inputted from the state variable storing part(12); a forth register(20) of 32 bit length storing reception state number(N(R)) temporarily inputted from the state variable storing part(12); a multiplexor(22) outputting data stored in the first, second, third and forth register in sequence according to the count signal of the counter(10); and a FIFO control part(26) storing the outputted value from the multiplexor(22) in an AAL FIFO(24) according to the signal of the counter(10).

Description

PDU generation circuit of 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 showing 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 diagram illustrating a PDU generation circuit of an SSCOP sublayer according to the present invention.

5 is a diagram illustrating a format of a USTAT-PDU.

* Explanation of symbols for main parts of the drawings

10: counter 12: state variable storage unit

14: first register 16: second register

18: 3rd register 20: 4th register

22: Multiplexed 24: ALL FIFP

26: FIFO control unit

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, a SSCOP (Service Specific) of a signal adaptation layer (SALL). Oriented Protocol (PDU generation circuit) that generates a STAT-PDU (Solicated Status Response) containing the status of SD-PDU reception, credit information for equivalent senders, if one or more new invalid SD-PDUs are found at the sub-layer. will be.

Recently, as the means of communication is rapidly dedigitized and the development of optical communication enables the transmission of a wide band, broadband ISDN (B-ISDN) is a next-generation communication network to meet various user needs. In this B-ISDN, not only the existing narrowband services such as remote meter reading, data terminal, telephone, facsimile, but also broadband services such as video telephony, video conferencing, high-speed data transmission, 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 ATM communication method is a method of communicating by asynchronous time division multiplexing (ATDM) based on a total of 53 bytes of ATM cells 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, and 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 adaptation layer (SAAL), and a higher protocol layer. Is divided into a Common Part AAL (CP AAL) and a Service Specific Convergence Sublayer (SSCS), and the service specific sublayer is SSCF (Service Specific Co-ordination Function) and SSCOP (Service). Specific connection Oriented Protocol). On the other hand, each of these layers has a mapping structure as shown in FIG. 2, which adds five octets of information to the data received from the SSCF upper layer and transfers the information to the SSCOP layer, and the SSCOP layer arranges the integer multiple of four octets. In order to add the PAD and predetermined trailer information to the CPCS layer, the CPCS layer delivers the PAD and the predetermined trailer to the SAR layer to add 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 transmits the data to the ATM data by adding a predetermined head having a 5-bit length to the transmitted data. SSCOP performs specific function of signal adaptation layer and is used to transfer variable length service data unit (SDU) between users and has the function of recovering lost or damaged SDU. Receives the signal data transfer request from the user or layer 3 of the signal adaptation layer and transmits it to the same layer transparently and without error. This corresponds to the existing layer 2, and corresponds to the user network interface (UNI) and the network node interface ( It can be used commonly for NNI: Network Node Interface, 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. At this time, the message transmitted or received at the SSCOP sublayer, that is, the SSCOP PDUS, controls 0 to 3 octets and 1 to 2 warts for aligning the data transmitted from the SSCF by an integer multiple of 4 octets, as shown in FIG. The maximum possible length is 65528 octets minus 8 octets of CPCS tracer from 65536 octets, which is the maximum possible length of CPCS PDU, so the remaining 65524 octets minus the control field of 4 octets is SSCOP-. The maximum possible length of the UU. Typically, the last four octets of control fields consist of two bits of pad length, two bits of unused portion, four bits of PDU type, and three octets of PDU variable. These control fields consist of the type of message conveyed and the SSCOP layer. Contains various information for performing a specific function. According to the present invention, when one or more new invalid SD-PUDs are found through an SSCOP connection, a PDU of an SSCOP layer that generates a USTAT-PDU containing credit information for a sender equal to the reception status of the SD-PDU is transmitted to a lower layer. The purpose is to provide a generating circuit.

A circuit of the present invention for achieving the above object comprises: a counter set to an initial value of 4 and down counted by receiving a predetermined start signal; 32-bit length first and second registers receiving the octet sequence number (N (S)) of the 3-octet length SD-PDU from the state variable storage unit: the maximum allowable reception state number ( 32-bit length third register temporarily received by receiving N (MR)): 32-bit length fourth register temporarily received by receiving reception state number (N (R)) from the state variable storage unit: A multiplexer for sequentially outputting data stored in the first register, the second register, the third register, and the fourth register according to the count signal of the counter: AAL outputs a value output from the multiplexer according to a signal of the control counter It consists of a FIFO control unit that stores the FIFO.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. 4 is a block diagram showing the configuration of the PDU generation circuit of the SSCOP layer according to the present invention, the counter 10 having an initial value set to 4 and receiving a predetermined start signal; 32-bit length first and second registers 14 and 16, which receive the sequence number N (S) of the 3-octet length SD-PDU from the state variable storage unit 12 and temporarily store the state variable storage. The third register 18 having a 32-bit length that is temporarily received and received the maximum allowable reception status number (N (MR)) from the section 12: The reception status number (N (R) from the state variable storage section 12; The fourth register 20 having a 32-bit length that is temporarily stored) is received): the first register 14, the second register 16, and the third register 18 according to the count signal of the counter 10. And a multiplexer 22 sequentially outputting data stored in the fourth register 20, and a value output from the multiplexer 22 according to the signal of the counter 10 in the AAL FIFO 24. It is composed of the Seek FIFO control unit 26.

The counter 10 is a 4-bit down counter, which receives a USTAT-PDU transmission signal input from the state control unit of the SSCOP and down counts it. The state variable storage unit 12 stores variables according to each state of the SSCOP. The state variables of the SSCOP PDUs are mapped to the factors constituting the field. The state variables of these SSCOPs are shown in Table 3 below. Same as

In particular, the present invention relates to VR (MR) and VR (R), where VR (MR) refers to the number of the first SD-PUD which is not allowed by the receiver. Generally, VR (H) is the maximum expected state. Must be greater than number

VR (R) indicates the number of consecutive SD-PDUs that are expected to be received next, and increases with the reception of consecutive SD-PDUs.

The format of the USTAT-PDU generated according to the present invention is composed of four words, as shown in FIG. 5, wherein the first and second words include a list of sequence numbers of the transmitted SD-PDUs. 3 words are mapped with N (MR) indicating the number of SD-PDUs that are not allowed at the receiving end, and the 4th word is a 4-bit PDU type indicating the PDU type and a subsequent SD scheduled to be received next. The PDU numbers match.

The first and second registers 14 and 16 are each composed of 32 bits to map the first and second words. One octet is an unused portion, a predetermined pad is mapped, and two to four octets are represented. The list of sequence numbers of the transmitted SD-PDUs is mapped.

The third register 18 maps the third word of the SD-PDU, wherein a first octet is an unused portion, and a second to fourth octet is connected to the state variable storage 12. Phosphorus N (MR) is mapped to N (MR). The fourth register 20 generates a fourth word, receives a predetermined PDU type, stores it in an upper octet, and whenever the predetermined PDU is generated, the fourth register 20 is connected to the state variable storage unit 12 in the lower three octets. (N) is mapped. The multiplexer 22 selects the first register 14, the second register 16, the third register 18, and the fourth register 20 under the control of the counter 10 and sequentially outputs them. . The FIFO control unit 26 causes the word output from the multiplexer 22 to control the AAL FIFO 24 by the counter signal generated while the counter 10 is operating.

The operation of the present invention configured as described above will be described in detail.

The USTAT-PDU generated in the present invention is used to transmit the reception status of the SD-PDU and the credit information of the equivalent sender when one or more invalid SD-PDUs are found between the peers. The format is shown in FIG. Without data, as shown, a list of received SD-PDUUs, indicating the number of SD-PDUs not allowed at the receiving end (N (MR)), a 4-bit PDU type, and subsequent contiguous expected to be received. The numbers of SD-PDUs are mapped.

If a signal to transmit a USTAT-PDU from the outside is input to the counter 10, it is counted down. The counter 10 counts down and the signal output for each count is input to the multiplexer 22 and the FIFO control unit 26, and the multiplexer 22 inputs a register value corresponding to a word of each PDU according to the counter. Select and output the AAL FIFO 24 by storing the output from the multiplexer 22 by controlling the AAL FIFO 24 by the output of the counter 10. Is generated.

Claims (1)

The counter 10 and down counting the initial value is set to 4 to receive a predetermined star signal: Input the sequence number (N (S)) of the SD-PDU of three octets long from the state variable storage unit 12 First and second registers 14 and 16 having a length of 32 bits received and temporarily stored: 32 bits which are temporarily stored after receiving the maximum allowable reception status number N (MR) from the state variable storage unit 12. Third register 18 having a length: 32-bit long fourth register 20 receiving the reception state number N (R) from the state variable storage unit 12 and temporarily storing it: the counter 10 A multiplexer 22 sequentially outputting data stored in the first register 14, the second register 16, the third register 18, and the fourth register 20 according to the cart signal of PDU generation of SSCOP composed of FIFO controller 26 for storing the value output from the multiplexer 22 in the AAL FIFO 24 according to the signal of the counter 10. Circuit.