JPH07321806A - Pointer insertion device - Google Patents

Abstract

PURPOSE:To provide a pointer insertion device capable of judging and inserting pointer information even when data length and the pointer information that can be housed in a cell are always changed. CONSTITUTION:A memory readout counter 30 reads out user data of data length corresponding to the pay-load specification signal 63 of the cell instructed by a pointer information insertion judging circuit 60. A frame counter 40 counts the data length up to the frame end of the user data based on a frame leading position information signal 12, and outputs a frame data signal 41 representing the data length. The pointer information insertion judging circuit 60 judges the insertion/non-insertion of the pointer information based on the data length by the frame data signal 41 and a sequence number by a sequence data signal 51, however, renders judgement to permit the insertion of exceptional pointer information also when a user data leading position is deviated from a prescribed range set in advance.

Description

Detailed Description of the Invention

[0001]

The present invention has a frame structure,
ATM (Asynchronous Transfer)
Mode: asynchronous transfer mode) A pointer insertion device belonging to an ATM communication device for transmitting user data to be cellized by a communication method, and more specifically, a pointer insertion device included in an area allocated on a payload in a cell and having user data. The present invention relates to a pointer insertion device that performs insertion determination and insertion of pointer information indicating the frame head position.

[0002]

2. Description of the Related Art Conventionally, G.K. 70
7-G. 709 and G.G. 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 accommodated in the payload area of the STM frame is designated by the pointer offset value. In the synchronous network, since the timing signals used in each station are all synchronized, the phase of the virtual container in the STM frame normally does not change and the pointer value becomes constant.

On the other hand, when user data having a frame structure is accommodated in a cell by ATM transmission, CCIT is used.
I. T. Draft User data is made into cells using the pointer information recommended in 363. This AT
Different from the pointer information of the STM method, the pointer information in the M transmission does not always allocate the pointer area in the cell, the sequence number indicating the cell transmission order is an even number, and the range that can be indicated by the pointer offset value. The pointer information is inserted into the cell only when the frame of the user data is at the beginning of the frame, 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 above-mentioned ATM communication method, 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. Further, the pointer offset value relating 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 the user data having the frame phase in the ATM cell as described above, it is necessary to form the cell by using the constantly changing pointer information.
Conventionally, no technique has been developed for processing such fluctuating pointer information.

The present invention has been made to solve such a problem, and its technical problem is to determine whether or not to 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, a pointer insertion device having a frame structure and including pointer information indicating a frame head position of user data transferred in cells by the ATM communication system in the cell. At
Storage means for accumulating user data, user data reading means for reading the user data from the storage means by the length of the user data included in the cell, counting means for counting the data length of the user data up to the end of the frame, and cell sequence A sequence number generation means for generating a number, a pointer information generation means for generating pointer information according to the data length, a judgment as to whether or not to insert the pointer information into the cell based on the data length and the sequence number, and the pointer The pointer information insertion determining means includes a pointer information insertion determining means for generating a selection control signal when inserting information, and a pointer inserting means for inserting pointer information into a cell in accordance with the selection control signal. The selection control signal is assumed to include the content confirmed whether it is within the predetermined range. Together to generate a pointer insertion device for the frame start position is different cells depending on the insertion of subsequent said pointer information to be processed is obtained.

Further, according to the present invention, in the above pointer insertion device, the pointer information insertion determination means makes a determination that permits insertion of exceptional pointer information when the frame head position deviates from a predetermined range. Is obtained.

Further, according to the present invention, in the above pointer insertion device, the pointer information insertion determination means generates a payload type signal corresponding to the corresponding cell when it is determined that exceptional pointer information is inserted, A pointer insertion device for transmitting the payload type signal to the user data reading means can be obtained.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The pointer inserting apparatus of the present invention will be described in detail below with reference to the accompanying drawings. Figure 1
FIG. 3 is a block diagram showing the basic configuration of a pointer insertion device according to an embodiment of the present invention.

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

In this pointer insertion device, user data is stored from the user data signal a input from the terminal T1 for the payload length of the cell, and the frame start position of the user data is sent from the frame start pulse b input from the terminal T2. Cellized memory 10 for storing information and terminal T3
A memory write which generates a memory write address signal 21 for taking in user data as a cellized frame structure in accordance with a frame pulse c input from the memory cell and sends the memory write address signal 21 to the cellized memory 10. In accordance with the built-in counter 20 and the cell pulse d input from the terminal T4, the memory read address signal 31 for reading the user data of the data length included in the cell from the cellized memory 10 is generated, and the memory read address signal 31 is generated. A memory read counter 30 for sending 31 to the cellized memory 10 is provided.

The pointer insertion device also includes a frame head position information signal 1 read from the cellized memory 10.
A frame counter 40 that counts the data length of the user data up to the end of the frame based on 2 and generates a frame data signal 41, a sequence number generation circuit 50 that generates a sequence data signal 51 that indicates the sequence number of the cell, and data. A pointer information generation circuit 70 that generates a pointer data signal 71 including pointer information to be included in the cell according to the length, and whether to insert the pointer information into the cell is determined based on the frame data signal 41 and the sequence data signal 51. However, when the pointer information is inserted, the pointer information insertion determination circuit 60 that generates the selection control signal 62 and the pointer data signal 71 sent from the pointer information generation circuit 70 according to the selection control signal 62 are read from the cellized memory 10. Combined with the user data cellized signal 11 Insert the pointer information to the cell, and a pointer inserting circuit 80 for generating an output cell data signals 61 are provided by the.

Of these, the pointer information insertion determination circuit 60
Generates a selection control signal 62 as contents for confirming whether or not the frame start position in the pointer information is within a predetermined range, and processes cells having different frame start positions according to subsequent insertion of pointer information. set to target.

On the other hand, the pointer information insertion determination circuit 60 is
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 exceptional insertion of the pointer information
And sends the payload type signal 63 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 next from the cellized memory 10, and even when the data length that can be accommodated in the cell and the pointer information change, Works to make insertion decisions and insertions.

FIG. 2 shows an example of a cell format used in the pointer insertion device shown in FIG.
This cell includes a 5-byte header area S1, a sequence number SN (Sequence Number) and an SN.
P (Sequence Number Protect)
Ion) including 1-byte SN / SNP area S2 and 4
It is composed of a 7-byte payload area S3.

The header area S1 is mainly used for identifying the destination of the cell from the transmission side to the reception side and for protecting the header from bit errors. The SN / SNP area S2 is
It is used to maintain the temporal continuity of user data, and the sequence number SN here indicates SC (Sequence Count) and CSI (C) indicating a count of 0 to 15.
oversubscriber Subscriber Indic
ation) and. The payload area S3 can accommodate 47 bytes of user data, but the accommodable length of user data differs depending on whether or not the pointer information P is accommodated.

FIG. 3A shows a case where the pointer information P is inserted. Here, the pointer information P constitutes a 1-byte pointer information area S3 _P , and the payload area S3 _a is 46 bytes. Has become. Also, FIG. 3 (b)
Shows the case where the pointer information P is not inserted.
Here, the entire 47 bytes form the 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 C, respectively.
It is distinguished by whether the SI bit value is 1 or 0. That is, the pointer information P is not always inserted, and is inserted when SC is an even number and the frame start position of the user data is in the payload range that can be indicated by the pointer information P. FIG. 4 shows an example in which the frame head position information F is designated as the pointer information P.

By the way, the allowable payload range that can be designated by the pointer information P at normal times is, as shown by the hatched lines in FIG. 5, the payload range of the cell in which the pointer information P is accommodated 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 instructed in the range (0 to 92) of the pointer offset value which is predetermined according to the payload allowable range at the normal time,
As described above, the pointer offset value relating to the 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. As a result, the frame start position information F of the user data designated by the pointer information P moves to a different cell located next to the next next cell, not to the next target cell, as shown in FIG. It exceeds the P instructable range.

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

Next, the processing operation of the pointer insertion device shown in FIG. 1 will be described. However, here, it is assumed that the user data signal a whose data length is 104 bytes is input. In this pointer insertion device, another processing is performed every time the cell pulse d is input to the memory read counter 30. First, the memory read counter 30 corresponds to the 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 instructed by the pointer information insertion determination circuit 60. User data is read from the cellized memory 10 and the user data cellized signal 11 is output from the cellized memory 10.

When reading user data from the cellized memory 10, the frame counter 40 uses the cellized memory 1
Based on the frame head position information signal 12 output from 0, the data length up to the frame end of the user data is down-counted each time one byte is read, and the frame data signal 41 indicating the result of counting this data length is generated.
At this time, the frame counter 40 changes the cell memory 10
If the frame start position information signal 12 read from indicates the frame start 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 included in the frame data signal 41 is displayed.
The insertion or non-insertion of the pointer information P is determined based on the condition shown in Table 1 from the E value and the SC value of the current sequence number SN included in the sequence data signal 51.

[0024]

[Table 1] 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, when the FE value is less than the offset value "92", it is judged 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 exceptional pointer value described above, and it is determined that “pointer insertion” needs to be performed. Further, when the FE value is equal to or greater than the offset value “94”, it is determined that “pointer is not inserted”.

When the pointer information insertion determining circuit 60 determines that the pointer information P needs to be inserted, the pointer inserting circuit 80 offsets the pointer data signal 71 generated by the pointer information generating circuit 70 (that is, the FE value). Is inserted into the output cell data signal 61 at a required timing by the selection control signal 62.

Further, the pointer information insertion judgment circuit 60 continuously makes a judgment as to whether or not the pointer information P is inserted not only in the cell to be transmitted now but also in the cell to be transmitted next, and in accordance with this result, next. Payload type signal (P format signal or No
n-P format signal) 63 to the memory read counter 3
Send to 0.

[0028]

As described above, according to the pointer insertion device of the present invention, the data length is counted every time the user data is read from the storage means and the variable offset value of the pointer information is generated. Even if the data length that can be accommodated in the cell and the pointer information constantly change, it is possible to determine and insert the pointer information. Further, in the case of this pointer insertion device, a cell having a different frame start position of user data designated by the pointer information is processed every time the pointer information is inserted, and the frame start position falls within a predetermined range. If you deviate,
Since the exceptional pointer information can be inserted, the output cell data signal including the user data by the ATM communication method can be transferred quickly and rationally.

[Brief description of drawings]

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

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

3 shows the payload area of the cell shown in FIG. 2, where FIG. 3A shows the accommodable length of user data when pointer information is inserted, and FIG. 3B shows pointer information. It shows the accommodable length of user data when it is not inserted.

FIG. 4 shows an example of a case where frame head position information is designated as pointer information in the case of FIG.

FIG. 5 shows an allowable payload range that can be designated by pointer information in the normal case.

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

FIG. 7 is a diagram showing an example of designating frame head position information of user data by using a pointer offset value “93” in the case of FIG. 6;

[Explanation of symbols]

 10 Cellized Memory 20 Memory Write Counter 30 Memory Read Counter 40 Frame Counter 50 Sequence Number Generation Circuit 60 Pointer Information Insertion Judgment Circuit 70 Pointer Information Generation Circuit 80 Pointer Insertion Circuit

Front Page Continuation (72) Inventor Hitoshi Uematsu 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation (72) Yumi Ueda 1-6 Uchiyuki-cho, Chiyoda-ku, Tokyo Nihon Telegraph Phone Co., Ltd.

Claims (3)

[Claims] 1. A pointer inserting device having a frame structure and including pointer information indicating a frame head position of user data transferred in cells by an ATM communication system in the cell, and storing means for storing the user data. A user data reading means for reading the user data from the storage means for a user data length included in the cell, a counting means for counting the data length of the user data up to the end of the frame, and a sequence number for the cell. Sequence number generation means for generating, pointer information generation 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 However, when inserting the pointer information, a pointer for generating a selection control signal is generated. Data insertion determining means and pointer insertion means for inserting the pointer information into the cell in accordance with the selection control signal, wherein the pointer information insertion determining means determines whether the frame head position is within a predetermined range. A pointer insertion device, wherein the selection control signal is generated as containing the content of whether or not it is confirmed, and a cell having a different head position of the frame is processed according to subsequent insertion of the pointer information. 2. The pointer insertion device according to claim 1, wherein the pointer information insertion determination means determines that exceptional insertion of pointer information is permitted when the frame head position deviates from the predetermined range. Characteristic pointer insertion device. 3. The pointer insertion device according to claim 2, wherein the pointer information insertion determination means generates a payload type signal corresponding to a corresponding cell when the insertion of the exceptional pointer information is determined, A pointer insertion device, characterized in that the payload type signal is sent to the user data reading means.