JP2937750B2 - Pointer insertion device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a frame structure,
Asynchronous transfer mode (Asynchronous Tra)
nsfer Mode / hereinafter referred to as ATM) is a pointer insertion device belonging to an ATM communication device that transmits user data to be cellized by a communication system, and is specifically included in an area allocated on a payload in a cell. The present invention also relates to a pointer insertion device that performs insertion determination and insertion of pointer information indicating a frame start position of user data.

[0002]

2. Description of the Related Art Conventionally, G.I. 70
7-G. 709 and G.C. 781-G. STM (Synchronous Trans) recommended in 784
ferMode: synchronous transfer mode) In the communication method, ST
A pointer area is always allocated in the M frame, and the first byte of the virtual container contained in the payload area of the STM frame is indicated by a pointer offset value. In a synchronous network, since all timing signals used in each station are synchronized, the phase of the virtual container in the STM frame does not usually change, and the pointer value is constant.

On the other hand, when user data having a frame structure is accommodated in a cell by ATM transmission, the CCIT
The I.T. Using pointer information recommended in H.363, user data is converted into cells. This AT
Unlike the pointer information of the STM system, the pointer information in the M transmission does not always allocate a pointer area in the cell, and the sequence number indicating the cell transmission order is an even number and the pointer can be indicated by the pointer offset value. The pointer information is inserted into the cell only when the frame of the user data has the head of the user data, and the pointer area is allocated in the fixed-length payload at this time.

[0004]

When user data is accommodated in a cell by the ATM communication system described above, the data length of the user data that can be accommodated in the payload up to the end of the frame changes depending on the presence or absence of pointer information. The pointer offset value related to this pointer information always fluctuates as long as the frame length of the user data is a non-integer multiple of the payload length in the cell. When transmitting user data having a frame phase in an ATM cell as described above, it is necessary to convert the cell into cells using constantly changing pointer information.
Conventionally, no technology for processing such fluctuating pointer information has been developed.

The present invention has been made to solve such a problem, and a technical problem of the present invention is to determine and insert pointer information even when the data length that can be accommodated in a cell and the pointer information constantly change. It is to provide a possible pointer insertion device.

[0006]

According to the present invention, there is provided a pointer insertion apparatus which has a frame structure and includes pointer information indicating the start position of a frame of user data to be transferred as cells in the ATM communication system. At
Storage means for accumulating user data; user data reading means for reading the user data from the storage means for the length of the user data contained in the cell; counting means for counting the data length of the user data up to the end of the frame; sequence of cells Sequence number generating means for generating a number, pointer information generating means for generating pointer information in accordance with the data length, and determining whether or not to insert pointer information into a cell based on the data length and the sequence number. Pointer information insertion determining means for generating a selection control signal when information is inserted, and pointer inserting means for inserting pointer information into a cell in accordance with the selection control signal, wherein the pointer information insertion determining means has a frame start position determined in advance. The selection control signal is considered to include the content Is determined, and cells whose frame start positions are different in accordance with the subsequent insertion of the pointer information are processed, and insertion of exceptional pointer information is permitted when the frame start position deviates from the predetermined range. Is performed, and when the insertion of the exceptional pointer information is determined, a pointer insertion device that generates a payload type signal corresponding to the corresponding cell and sends the payload type signal to the user data reading unit is obtained.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described in detail with reference to the drawings. FIG.
1 is a block diagram showing a basic configuration of a pointer insertion device according to one embodiment of the present invention.

This pointer insertion device also has a frame structure, and has a function of including in a cell pointer information indicating a frame head position of user data to be transferred in cells by the ATM communication system.

This pointer insertion device accumulates user data for the payload length of the cell from the user data signal a input from the terminal T1, and outputs the frame start position information of the user data from the frame head pulse b input from the terminal T2. And a memory write address signal 21 for taking in user data as a cellularized frame configuration in accordance with a frame pulse c input from a terminal T3. A memory write counter 20 for sending out 21 to the cellular memory 10, and a memory read address signal for reading out from the cellular memory 10 user data corresponding to the data length included in the cell in accordance with the cell pulse d input from the terminal T4. 31 and converts the memory read address signal 31 into a cell. And a memory read counter 30 to be transmitted to memory 10.

[0010] The pointer insertion device also includes a frame head position information signal 12 read from the cellular memory 10.
A frame counter 40 that counts the data length of the user data to the end of the frame based on the frame length, and generates a frame data signal 41; A pointer information generation circuit 70 that generates a pointer data signal 71 including pointer information to be included in a cell in accordance with the frame data signal 41 and the sequence data signal 51 determines whether or not to insert pointer information into a cell. When the pointer information is to be inserted, the pointer information insertion determination circuit 60 for generating the selection control signal 62 and the pointer data signal 71 sent from the pointer information generation circuit 70 in accordance with the selection control signal 62 are read from the cell memory 10. Combining with user data cell signal 11 And a pointer insertion circuit 80 which inserts the pointer information in the cell, to generate an output cell data signal 61 by.

Among them, the pointer information insertion determination circuit 60
Generates a selection control signal 62 as content for confirming whether or not the frame head position in the pointer information is within a predetermined range, and processes cells having different frame head positions in accordance with subsequent insertion of pointer information. set to target.

On the other hand, the pointer information insertion determination circuit 60
When the frame head position in the pointer information deviates from the predetermined range, the payload type signal 63 corresponding to the corresponding cell for permitting the insertion of the exceptional pointer information
Is transmitted to the memory read counter 30 to control the memory read counter 30. Therefore, the pointer information insertion determination circuit 60 has a function of determining the data length of the user data to be read out from the cell memory 10 next, and the pointer information of the pointer information is changed even when the data length that can be accommodated in the cell and the pointer information change. Works to perform insertion determination and insertion.

FIG. 2 shows an example of a cell format used in the pointer insertion device shown in FIG.
This cell has a 5-byte header area S1, sequence numbers SN (Sequence Number) and SN.
P (Sequence Number Protect)
ion), a 1-byte SN / SNP area S2 including
And a 7-byte payload area S3.

The header area S1 is mainly used to identify the destination of the cell from the transmitting side to the receiving side, and to protect the header from bit errors. The SN / SNP area S2 is
The sequence number SN is used to maintain temporal continuity of user data. Here, the sequence number SN and the CSI (Sequence Count) indicating the count of 0 to 15 are used.
inverted Sublayer Indic
ation). The payload area S3 can accommodate 47 bytes of user data, but the accommodable length of the user data differs depending on whether or not the pointer information P is accommodated.

[0015] FIG. 3 (a) shows a case where the pointer information P is inserted, wherein which forms the pointer information area S3 _P pointer information P is 1 byte, the payload area S3 _a 46 byte It has become. FIG. 3 (b)
Indicates a case where the pointer information P is not inserted.
Here all of the 47 bytes forms a payload area S3 _b. Here, the cell format including the pointer information P (P format) and the format not including the pointer information P (Non-P format) are respectively C
It is distinguished by whether the SI bit value is 1 or 0. That is, the pointer information P is not always inserted, but is inserted when the SC is an even number and the frame start position of the user data is within the payload range that can be indicated by the pointer information P. FIG. 4 shows an example of a case where the frame head position information F is designated as the pointer information P.

By the way, as shown by hatching in FIG. 5, the payload allowable range in which the pointer information P can be indicated at normal times is the payload range of the cell containing the pointer information P, and the payload range of the cell following this. And
The pointer offset value at this time takes a value from 0 to 92.

However, if the pointer information P is to be designated within a predetermined range (0 to 92) of the pointer offset value according to the normal payload allowable range,
As described above, the pointer offset value related to the pointer information always changes as long as the frame length of the user data is a non-integer multiple of the payload length in the cell. As a result, as shown in FIG. 6, the frame start position information F of the user data indicated by the pointer information P moves not to the next cell of interest but to the next different cell located next. It exceeds the range in which P can be indicated.

Therefore, if the exceptional pointer offset value "93" is used, as shown in FIG. 7, the frame head position information F of the user data is stored at the head of the next next cell located next. can do. At this time, the frame head position information F of the user data is indicated by two pieces of pointer information P having both “93” and “0”.

Next, the processing operation of the pointer insertion device shown in FIG. 1 will be described. Here, it is assumed that a user data signal a having a data length of 104 bytes is input. In this pointer insertion device, another process is performed each time the cell pulse d is input to the memory read counter 30. First, the memory read counter 30 has a data length (46 bytes or 47 bytes) corresponding to the payload type signal (P format signal or Non-P format signal) 63 of the cell indicated by the pointer information insertion determination circuit 60. The user data is read from the cell memory 10, and the cell memory 10 outputs a user data cell signal 11.

When reading user data from the cellular memory 10, the frame counter 40 reads the user data from the cellular memory 1.
Based on the frame head position information signal 12 output from 0, the data length up to the end of the frame of the user data is counted down every time one byte is read, and a frame data signal 41 indicating the result of counting this data length is generated.
At this time, the frame counter 40 stores the
If the frame head position information signal 12 read out from the register indicates the frame head position, the frame data signal 41 indicating the frame length of 104 bytes is transmitted.

In the pointer information insertion determination circuit 60, F indicating the current data length contained in the frame data signal 41
Based on the E value and the SC value of the current sequence number SN included in the sequence data signal 51, the insertion or non-insertion of the pointer information P is determined based on the conditions shown in Table 1.

[0022]

[Table 1] More specifically, when the SC value of the cell to be transmitted is an even number, the frame start position information F of the user data can be indicated by the pointer information P within a normal allowable range (pointer offset value 0 to 92). Whether or not the current FE
The determination is made by comparing the value and the offset value “93”.

At this time, if the FE value is equal to or less than the offset value "92", it is determined that "pointer insertion" is necessary. Also, F
When the E value is equal to the offset value “93”, the offset value “93” is used as the above-described exceptional pointer value, and it is determined that “pointer insertion” needs to be performed. Further, when the FE value is equal to or larger than the offset value “94”, it is determined that “pointer is not inserted”.

When the pointer information insertion determination circuit 60 determines that the insertion of the pointer information P is necessary, the pointer insertion circuit 80 determines the offset value (ie, FE value) of the pointer data signal 71 generated by the pointer information generation circuit 70. Is inserted into the output cell data signal 61 at a required timing by the selection control signal 62.

Further, the pointer information insertion determining circuit 60 continuously determines whether or not the pointer information P is to be inserted or not inserted into the cell to be transmitted next as well as the cell to be transmitted at present. Payload type signal (P format signal or No.
n-P format signal) 63 to the memory read counter 3
Send to 0.

[0026]

As described above, according to the pointer insertion device of the present invention, the data length is counted each time the user data is read from the storage means, and the offset value of the fluctuating pointer information is generated. Thus, even when the data length that can be accommodated in the cell and the pointer information constantly change, the insertion determination and insertion of the pointer information can be performed. In addition, in the case of this pointer insertion device, every time the pointer information is inserted, a cell having a different frame start position of the user data indicated by the pointer information is set as a processing target, and the frame start position is set to a predetermined range. If you deviate,
Since the exceptional pointer information can be inserted, the output cell data signal including the user data can be quickly and rationally transferred by the ATM communication system.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of a pointer insertion device according to one embodiment of the present invention.

FIG. 2 shows an example of a cell format used in the pointer insertion device shown in FIG.

3A and 3B show a payload area of the cell shown in FIG. 2; FIG. 3A shows the length of user data that can be accommodated when pointer information is inserted; FIG. It shows the user data accommodable length when not inserted.

FIG. 4 shows an example in the case of FIG. 3A, in which frame head position information is indicated as pointer information.

FIG. 5 shows a payload allowable range in which pointer information can be indicated in a normal state in the case of FIG. 4;

FIG. 6 shows an example in which the frame start position information of the user data deviates from a normal instructable range in the case of FIG. 5;

FIG. 7 shows an example in which frame pointer position information of user data is indicated using a pointer offset value “93” in the case of FIG. 6;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Cellular memory 20 Memory write counter 30 Memory read counter 40 Frame counter 50 Sequence number generation circuit 60 Pointer information insertion determination circuit 70 Pointer information generation circuit 80 Pointer insertion circuit

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hitoshi Uematsu 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Inventor Hiromi Ueda 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Japan (56) References JP-A-4-100347 (JP, A) JP-A-5-240157 (JP, A) JP-A-5-302838 (JP, A) ITU-T Recommendation I . 363 (58) Field surveyed (Int.Cl. ⁶ , DB name) H04L 12/28

Claims (1)

(57) [Claims] 1. A pointer insertion device having a frame structure and including pointer information indicating a frame start position of user data to be transferred in a cell by an asynchronous transfer mode communication method in said cell, wherein said user data is stored. Storage means; user data reading means for reading the user data from the storage means for a user data length included in the cell; counting means for counting the data length of the user data up to the end of a frame; sequence of the cells Sequence number generating means for generating a number, pointer information generating means for generating the pointer information according to the data length, and whether or not to insert the pointer information into the cell based on the data length and the sequence number And generates a selection control signal when inserting the pointer information. Pointer information insertion determining means for inserting the pointer information into the cell according to the selection control signal, wherein the pointer information insertion determining means has the frame head position within a predetermined range. The selection control signal is generated as containing the content that has been confirmed whether or not the cell whose head position is different according to the subsequent insertion of the pointer information is processed, and the frame head position is within the predetermined range. When the deviation deviates from the above, it is determined that the insertion of the exceptional pointer information is permitted. When the insertion of the exceptional pointer information is determined, a payload type signal corresponding to the corresponding cell is generated. A pointer insertion device for transmitting to the user data reading means.