JP2828080B2 - Pointer monitoring device at cell conversion in AAL1 - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to AAL1 (ATM Ad
aptation Layer Type 1) Synchronous transfer mode (ST
M) STM / AT for converting a signal into a fixed packet (ATM cell) for each channel of a synchronous transfer mode (ATM) circuit
The present invention relates to an SDT (Structured Data Transfer) method of M conversion, and more particularly to a monitoring device for a pointer value to be output.

[0002]

2. Description of the Related Art AAL type 1 (ATM Adaptation L)
When transferring a frame structure when converting a CBR (Constant bit rate) signal into cells in the ayer Type 1), the frame head position information is transferred using a pointer. When performing the celling process, a process of predicting and adding a pointer value indicating the head position based on the frame length for each accommodation VP (Virtual Path) is performed. This prediction operation is performed by predicting the next pointer value by subtracting the output byte number from the frame length byte number for each cell output.

[0003] Regarding a pointer indicating the head position of a frame, ITU-T Recommendation, I. AAL type 1 of 363
Stipulates that the first cell transmitted after an ATM connection is established is a P-format cell
R-PDU (Segmentation And Reassembly-Protocol Da
This is a cell in which the SC (Sequence count) of the te Unit) header is 0 and the pointer is 0. "However, there is no description of pointer monitoring during cellization.

[0004]

The prior art described above is
Since the calculation of the pointer value is performed by the prediction operation based on the frame length of each VP, if the pointer added at the time of cell formation is shifted due to a malfunction of the device, an incorrect pointer is added forever. May be lost. In addition, the ITU-T recommendation described in the prior art, I. Since the rules for pointers of AAL type 1 in 363 do not show the method of monitoring the pointer at the time of cell conversion, the pointer may not be correctly added depending on the implementation method.

It is an object of the present invention to provide an AAL type 1 S
An object of the present invention is to provide a pointer value monitoring device that efficiently checks whether a pointer conforming to the DT method is correctly added without complicating a predicted pointer monitoring process.

[0006]

Means for Solving the Problems AAL type of the present invention
The pointer monitoring device at the time of cell conversion in e1 includes a head position monitoring unit that monitors a frame head position at fixed cycles, a pointer value monitoring unit that monitors a pointer value at fixed cycles, and a number of output cycles at each VP. And an output cycle monitoring means for issuing a monitoring instruction to the frame head position monitoring means and the pointer monitoring means every fixed cycle.

Since the pointer value output every fixed cycle is monitored, it is possible to correct even if an erroneous pointer value is being added.

Since the head position data of the frame is monitored every fixed cycle, it is possible to monitor whether the pointer value points to the head data of the true frame.

[0009]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a first embodiment of the present invention.

The input buffer 1 has a two-sided configuration.
It has a surface on which frame data is written from the outside and a surface on which the frame data is referenced internally. CM (Control Memor
y) Data 2 is data indicating a relationship between TS (time slot) and VP of input data having a frame structure, and includes data / start position data write control unit 5, start position data generation unit 4, pointer management / frame length detection. Output to the unit 8.
The head position data generator 4 generates data indicating the frame head position for each VP from the CM data, and the data is written together with the data into the cell buffer 3 as frame head position information. The data / head position data writing control unit 5 generates and outputs an address for writing the input data and the head position data to the celling buffer 3 based on the CM data 2, and further outputs the data to the data accumulation management unit 6. Output address. The celling buffer 3 is divided into banks for each VP, and the data to be written are input data and head position data. The data storage management unit 6 receives the write address from the data / head position data write control unit 5, further receives the read address from the data read unit 7, and monitors the data storage amount of the cell buffer 3 for each VP. When it is determined that data enough to be converted into cells has been stored, a read instruction is notified to the data reading unit 7. The data reading section 7 receives a VP value from which data can be read from the data accumulation management section 6 and outputs a read address to the celling buffer 3.
Further, it outputs the read VP value to the output cycle monitor 9 and outputs the number of output bytes to the pointer management / frame length detector 8 for each VP. The pointer management / frame length management unit 8 receives the CM data 2, detects the frame length for each VP, and further predicts a pointer value from the output byte number information and the frame length information for each VP from the data reading unit 7. , And outputs the predicted pointer value to the pointer value monitoring unit 11. The output cycle monitoring unit 9 receives the VP value read from the data reading unit 7, monitors the output cycle for each VP, and issues a monitoring instruction to the head position monitoring unit 10 and the pointer value monitoring unit 11 for every fixed cycle. I have. The frame head position monitoring unit 10 receives the payload data and the head position data from the celling buffer 3, monitors the frame head position at the timing specified by the output cycle monitoring unit 9, and stores only the payload data in the header addition unit 12. Output to The pointer value monitoring unit 11 receives the predicted pointer value from the pointer management / frame length management unit 8, monitors the pointer value at the timing specified by the output cycle monitoring unit 9, and outputs the pointer value to the header addition unit 12. . The header adding unit 12 receives the payload data from the head position monitoring unit 10 and
, A pointer value is added to the data, an ATM header, a SAR-PDU header, and a pointer value if necessary, and the data is output as a cell.

FIG. 2 shows CM data 2 for input data.
4 shows the CM data stored in the first position data and the start position data generated by the start position data generation unit 4. FP as shown
And data are input, head position data indicating a frame head position for each VP is generated from CM information indicating a relationship between each TS and the VP. In this example, “1” is assigned to the frame start position TS for each VP.

Next, the operation of this embodiment will be described in detail with reference to FIG. It is assumed that the celling is performed for each frame, and the input data is written in the celling buffer 3 divided into banks for each VP with reference to the CM data 2. At this time, the frame head position data generated by the head position data generator 4 is also written in parallel. Referring to FIG. 2, the frame start position data is data that gives “1” to the TS in which the data for each VP is first placed based on FP (Frame Pulse) indicating the start of the frame. In FIG. 2, TS1 is the head of VP0, T
S2 is the head of VP1, TS4 is the head of VP2, TS7 is the head of VP3, TS9 is the head of VP4, TS10 is the VP
5 at the top.

The data storage management unit 6 manages the data storage status for each VP, and outputs a read permission to the data read unit 7 when data of one cell is stored. The output cycle monitoring unit 9 receives the VP value read from the data reading unit 7, monitors the number of output cycles for each VP, and issues a monitoring instruction to the head position monitoring unit 10 and the pointer monitoring unit 11 when the number of cycles reaches a specified number. And monitors the cell of SC0. The specified number of cycles is, for example, a common multiple of the frame length of each VP, and is always SC0 and pointer 0 after the specified number of cycles if output from the cell of SC0 and pointer 0 after initialization.
Will be output. By defining the monitoring cycle in this way, the output monitoring cycle can be managed in common for each VP. In the frame head position monitoring unit 10,
The head position data of the payload is monitored, and whether the position is really the head position is monitored, and the payload data is output to the header adding unit 12. If there is a shift in the head position, the celling buffer 3 is initialized. The pointer value monitoring unit 11 receives the predicted pointer value at that time, monitors whether the value is 0, and outputs a correct pointer value to the header adding unit 12. In the header adding unit 12, an ATM header and SAR-
A PDU header (a pointer at the time of P-format) is added, and the cell is output as a cell.

As described above, instead of monitoring the head positions of all data, S which must occur in all VPs
By monitoring the cell of C0 and pointer 0 every prescribed cycle, it becomes possible to correct the case where the pointer value is shifted,
Further, the monitoring process can be simplified.

FIG. 3 is a block diagram showing a second embodiment of the present invention.

In this embodiment, an output frame number monitor 13 is provided in place of the output cycle monitor 9 shown in FIG. The output frame number monitoring unit 13 includes the data reading unit 7
VP and the number of bytes currently being read, and further receives frame length information for each VP from the pointer management / frame length detector 8 and monitors the number of output frames. When the number of output frames reaches 375, for example, a monitoring instruction is issued to the head position monitoring unit 10 and the pointer value monitoring unit 11. If the first output cell after initialization for each VP is a cell with SC0 and a pointer value of 0, the cell with SC0 and pointer value of 0 should be output again when the number of output frames reaches 375. The same monitoring as in the form can be performed.

[0017]

As described above, the present invention has the following effects.

(1) Since the monitoring of the pointer value added at the time of cell formation and the monitoring of the frame head position are performed, if the pointer value added at the time of cell formation is shifted due to a device malfunction, it is necessary to correct the pointer value to the correct value. It becomes possible.

(2) Since the monitoring target is the cell of SC0 and pointer 0 for each VP, the ITU-T recommendation, I.C. 3
It is possible to monitor whether or not the cycle of the pointer is in accordance with the rules regarding the 63 AAL type 1 pointers.

(3) Since the monitoring of the pointer value is performed not in every cycle but in a fixed period, the monitoring of the pointer value added at the time of cell formation can be easily and efficiently performed.

[Brief description of the drawings]

FIG. 1 shows AAL type 1 according to a first embodiment of the present invention.
FIG. 3 is a block diagram showing a pointer monitoring device at the time of cell formation in FIG.

FIG. 2 shows input frame data and C corresponding to FP.
It is a time chart of M data and head position data.

FIG. 3 shows AAL type 1 according to a second embodiment of the present invention.
FIG. 3 is a block diagram showing a pointer monitoring device at the time of cell formation in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Input buffer 2 CM data 3 Celling buffer 4 Head position data generation part 5 Data / head position data writing control part 6 Data accumulation management part 7 Data reading part 8 Pointer management / frame length detection part 9 Output cycle monitoring part 10 Head position monitoring unit 11 Pointer value monitoring unit 12 Header addition unit 13 Output frame number monitoring unit

Claims (3)

(57) [Claims] 1. A pointer monitoring device for converting a synchronous transfer mode signal corresponding to AAL1 into a fixed-length packet for each channel of an asynchronous transfer mode line in a cell in the SDT method of STM / ATM conversion. A head position monitoring means for monitoring a frame head position, a pointer value monitoring means for monitoring a pointer value for each constant cycle, a frame head position monitoring means for monitoring the number of output cycles for each VP, and for each fixed cycle. A output cycle monitoring means for issuing a monitoring instruction to the pointer value monitoring means.
Pointer monitoring device at the time of cell conversion in AL1. 2. A pointer according to claim 1, further comprising means for generating frame head position information for each VP from CM data indicating a relationship between the VP and the data in a byte unit for each time slot accompanying the input data having a frame structure. Monitoring device. 3. The pointer monitoring apparatus according to claim 1, further comprising means for detecting a frame length of each VP from the CM data and generating an internal management pointer value based on the frame length.