KR0129180B1 - A circuit for generation of pdu in sscop sublayer - Google Patents

Abstract

A PDU generating circuit for SSCOP auxiliary layer is provided, which includes a counter(10) for inputting certain start signal to down-count; first register(14) for inputting 2 bit pad length signal from the pad generating unit(12) and for inputting 4 bit PDU type signal to temporal store; a multiplexer(18) for successively outputting data stored in SSCOP FIFO(16) and data stored in first register(14) according to counting signal of the counter(10); a FIFO controlling unit(22) for storing output value of the multiplexer(18) to AAL FIFO(20) according to counting 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 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 an SSCOP sublayer according to the present invention.

FIG. 5A shows the format of a BGREJ-PDU. FIG.

(b) shows the format of the END-PDU.

(c) shows the format of the ENDAK-PDU.

* Explanation of symbols for main parts of the drawings

10: counter 12: pad generating unit

14: first register 16: SSCOP FIFO

18: Multiplexer 20: AAL FIFO

22: 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, SSCOP (Service Specific Oriented) of a signal adaptation layer BGREJ-PDU or END-PDU used to disconnect SSCOP between peers, and ENDAK-PDU used to verify that SSCOP is disconnected. PDU generation circuit that generates. 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; Broadband Integrated Services Digital Network) 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 Common Part AAL (CP AAL) and 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 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 without error. This corresponds to the existing layer 2, and is the user network interface (UNI) and the network node interface. Commonly used for (NNI; Network Interface), and its functions are shown in Table 2 below.

In the SSCOP sublayer, which performs the function as shown in Table 2, the signal flow of the signal adaptation layer shown in FIG. 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- You will understand two signals: invoke and CPCS-UNIT-signal. In this case, a message transmitted or received at the SSCOP sublayer, that is, an SSCOP PDU, is a pad of 0 to 3 octets and 1 to 2 words for aligning the data transmitted from the SSCF by an integer multiple of 4 octets The maximum possible length is 65528 octets minus 8 octets of CPCS trailers from 65536 octets, which is the maximum possible length of CPCS PDU, so the remaining 65524 octets of the SSCOP-UU minus the control field of 4 octets Maximum possible length Typically, the last four octets of the control field consist of two bits of pad length, two bits of unused portion, four bits of PDU type, and three octets of PDU variable. Contains various information for performing a specific function.

An object of the present invention is to provide a PDU generation circuit of an SSCOP layer that generates a BGREJ-PDU indicating that a connection request is rejected by a counterpart of an equivalent entity by a predetermined external signal and transmits the same to a lower layer. It is still another object of the present invention to provide a PDU generation circuit of an SSCOP layer that generates an END-PDU used for releasing connections between equivalent SSCOP entities and transmits the same to a lower layer. It is still another object of the present invention to provide a PDU generation circuit of an SSCOP layer that generates an ENDAK-PDU (END Acknowledgment-PDU) used to confirm that the SSCOP connection is released and transmits it to a lower layer.

A circuit of the present invention for achieving the above object comprises: a counter set to an initial value of 2 plus a word length of data transmitted from an SSCF layer to receive a predetermined start signal and down count; A 32-bit length first register receiving a 2-bit pad length signal from the pad generating unit, and receiving and storing a 4-bit PDU type signal temporarily; A multiplexer for sequentially outputting data stored in an SSCOP FIFO, '0' and a control field stored in the first register according to the count signal of the counter; The FIFO controller is configured to store a value output from the multiplexer in an AAL FIFO according to a signal of the control counter.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. 4 is a block diagram of a PDU generation circuit of an SSCOP layer according to the present invention, and is set to an initial value of 2 plus a word length of data transferred from an SSCF layer to receive a predetermined start signal and to count down. A counter 10; A 32-bit length first register 14 that receives a 2-bit pad length signal from the state variable storage pad generation unit 12 and temporarily stores a 4-bit PDU type signal; A multiplexer 22 sequentially outputting data stored in the SSCOP FIFO 16, '0' and data stored in the first register 14 according to the count signal of the counter 10; The AFI FIFO 20 stores the value output from the multiplexer 18 according to the signal of the counter 10. The counter 10 is transmitted from a higher layer, that is, a SSCF (Service Specific Coordination Function), and a word length signal of data stored in the SSCOP FIFO 16 plus 2 is set as an initial value, and the BGREJ inputted from the state control unit of the SSCOP. The PDU transmission signal is input and down counted. The word length signal is obtained from an integer multiple of a 32-bit word by adding 1 to 3 octets of PAD to the input data. In this case, down counting by adding 2 to the word length adds an 8 octet control field added to the SSCOP layer to the transmitted data.

The first register 14 is composed of 32 bits and prepares N words in an N word length BGREJ-PDU and is added to the data transferred to the SSCF by the selective output of the multiplexer 18. The pad length information and the predetermined PDU type added to the data are inputted and stored in the predetermined position. The pad generator 12 adds 1 to 3 octets of pads to fit the data transmitted to the SSCOP FIFO 16 into 32 bit words, and outputs the pad length information according to the length of the added PAD. . The SSCOP FIFO 16 stores data transferred from an upper layer, that is, SSCF, and these data are added to control layers stored in the first register 14 by a selective output of the multiplexer 18 and transmitted to the lower layer. do. The multiplexer 18 selects the SSCOP FIFO 18, '0', and the first register 14 under the control of the counter 10, and sequentially outputs the selected SSCOP FIFOs 18. The FIFO control unit 22 controls the AAL FIFO so that the data output from the multiplexer 18 is stored in the AAL FIFO 20 by the counter signal generated during the operation of the counter 10.

The operation of the present invention configured as described above will be described in detail. The BGREJ-PDU generated in the present invention is used to indicate that a connection request from an equivalent entity of the SSCOP has been rejected between the equivalent entities, and the format is SSCOP transmitted from a higher layer as shown in FIG. 5 (a). 1 to 3 octets of pads are added to the UU to multiply the 32-bit word, and the SSCOP-UU data of N-2 words, the pad length indication of 2 bits, and the predetermined PDU type of 4 bits are displayed. Consists of When a signal for transmitting the BGREJ-PDU from the outside is input to the counter 10, a value obtained by adding 2 to the word length of data stored in the SSCOP FIFO 16 is set to an initial value of the counter 10 and down counted.

When the counter 10 counts down and the signal output for each count is input to the multiplexer 18 and the FIFO controller 22, the multiplexer 18 initially selects and outputs the stored value of the SSCOP FIFO controller 16. In addition, the FIFO control unit 22 controls the AAL FIFO 22 so that one PDU is generated by writing the output value of the multiplexer 18 to the AAL FIFO 20. The END-PDU generated in the present invention is used to disconnect the equivalent entities of the SSCOP between the equivalent entities, the format of which is configured as shown in FIG. 5 (b) so that the configuration is identical to the BGREJ-PDU. The same operation is also the same, and description is omitted. The ENDAK-PDU generated in the present invention is used to confirm the disconnection of the SSCOP between equivalent entities. The format is 4 bits without the SSCOP-UU transmitted from the upper layer as shown in FIG. Only certain PDU types consist of control fields. When a signal for transmitting the ENDAK-PDU from the outside is input to the counter 10, 2 is set to an initial value of the counter 10 and down counted.

When the counter 10 counts down and the signal output for each count is input to the multiplexer 18 and the FIFO control unit 22, the multiplexer 18 initially selects and outputs '0', and the FIFO control unit 22 Controls the AAL FIFO 22 to write the output value of the multiplexer 18 to the ALL FIFO 20, and then selectively outputs the input value of the first register 14 to generate one PDU. .

Claims (1)

A counter 10 which is set to an initial value obtained by adding 2 to the word length of data transmitted from the SSCF layer, and receives a predetermined start signal and down counts it; A first register 14 having a 32-bit length, which receives a 2-bit pad length signal from the pad generating unit 12, receives a 4-bit PDU type signal, and temporarily stores it; A multiplexer 22 sequentially outputting data stored in the SSCOP FIFO 16, '0' and data stored in the first register 14 according to the count signal of the counter 10; PDU generation circuit of the SSCOP sublayer composed of the FIFO control unit 22 which stores the value output from the multiplexer 18 in accordance with the signal of the counter 10 and stores the AAL FIFO 20.