JPH03220839A - Cell recovery control system - Google Patents

Abstract

PURPOSE:To attain early restoration of dissident state of consecutive cell recovery timing caused due to line clock interruption by discriminating a connection cell backward by one stage when a sequence number and a recovered timing number are dissident. CONSTITUTION:When a sequence number SN of a reception cell and a recovered timing number TN are dissident and a cell A to be received precedingly in the recovery timing at current point of time is extracted, the cell A is aborted. Moreover, when a reception cell B is connected backward the cell A in a buffer of a cell reception section 17, the cell B is extracted and compared with the recovery timing number TN at a current point of time. When they are coincident, the cell B is recovered. Thus, the dissident state of the cell recovery timing caused consecutively due to the line clock interruption is recovered early by discriminating the cell connected backward by one stage at the dissidence between sequence number SN and the recovered timing number TN.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a reproduction control system for fixed length data packets (hereinafter referred to as cells).

(Prior art) In a conventional cell reproduction control method, the cell reproduction side compares a reproduction timing number that is updated at a constant cycle with a sequence number indicating the reproduction time series of received cells, and then compares the reproduction timing number and sequence number. In the case of mismatch, there is a response by discarding the cell. According to this conventional method, there is a possibility that normal playback cannot be restored due to mismatch in playback timing.

For example, as shown in FIG. 8, when using a sequence number modulo Since the cells are discarded, regeneration of the cells becomes impossible for a long period of time.

(Problem to be solved by the invention) In this way, in the conventional cell reproduction control system, the reproduction timing number on the cell reproduction side is compared with the sequence number indicating the reproduction time series of the received cell, and if there is a mismatch, teeth,
Since this is handled by discarding cells, a discrepancy in playback timing occurs, making it impossible to restore normal playback.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a cell regeneration control method that eliminates this problem, performs proper regeneration, enables rapid recovery from a continued cell mismatch state, and avoids a long-term mismatch state. .

[Structure of the invention]

(Means for Solving the Problems) The cell reproduction control method of the present invention compares a sequence number indicating a reproduction time series added to a cell with a reproduction timing number updated at a constant cycle on the receiving side, and reproduces the cell. In a cell playback control method that performs the The sequence number of the subsequent fixed-length data packet is compared with the current reproduction timing number, and if they match, the subsequent fixed-length data packet is reproduced at the present time.

Further, in the cell playback control method of the present invention, in the above configuration, when the mismatch between the sequence number and the playback timing number continues for a certain period of time or more, the cell playback control method changes the sequence number to the latest playback timing after the certain time has elapsed. The fixed length data packet is replaced with the number TN and the fixed length data packet is reproduced again.

(Function) When a mismatch occurs between the sequence number of cell A and the playback timing number, if receiving cell B is connected after this cell A, the sequence number of cell B and the current playback timing number are Comparison is made, and if they match, cell B is reproduced. In this manner, by determining the connected cell one step later when the sequence number and the reproduction timing number do not match, it is possible to quickly recover from a continued mismatched cell reproduction timing state that occurs due to a line clock disconnection or the like. , Here, monitoring one step backward reduces the intensive processing load compared to monitoring several steps backward at the time of determination and determining whether or not there is a match.

In addition, when a mismatch state between the sequence number of the received cell and the playback timing number occurs, a mismatch state monitoring timer is started, and if the mismatch state continues for more than the set time of this timer, after this timer times out, The sequence number of the captured cell is replaced with the latest reproduction timing number to achieve normal reproduction timing synchronization.

If the mismatch between the sequence number of the received cell and the playback timing number continues for a predetermined period of time, the sequence number of the received cell is replaced with the latest timing number after the predetermined period of time has elapsed, and the sequence number of the received cell is replaced with the latest timing number. Since the minimum timing is synchronized, it is possible to avoid a long-term mismatched state.

(Embodiments) Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an embodiment of a cell transmission/regeneration device 100 that employs the cell regeneration control method of the present invention. First, the cell transmission operation will be explained. User information input from the terminal side is added to the cell forming section 12 via the terminal interface 11 from the terminal side reception line IO. The cell generator 12 divides user information into fixed length information. Then, at the time of cell formation, the sequence number counter generator 13 adds a modulo-structured sequence number SN to the ladder section of the jlifJ control of the cell. The cell to which this modulo-structured sequence number is added is sent to the network as a transmission cell by the cell transmission section 14 through the network side cell transmission line 15.

Next, the cell reception and reproduction operation will be explained. The received cells received from the network receiving line 6 are stored in the cell receiving section 17, which is composed of a buffer, in the order of arrival. Then, the cell reproducing unit 18 sequentially extracts the received cells from the cell receiving unit 17 at the timing of the reproduction timing number TN that is periodically generated from the reproduction timing counter generating unit 19, and sets the sequence number SN of the received cell and the reproduction timing. A comparison with the reproduction timing number TN periodically generated by the counter generating section 19 is performed. At this time, it is also determined whether the sequence number SN of the received cell exists within the range indicated by the window size designation unit 20. If it is normal, the terminal interface 11
The data is sent to the terminal side transmission line 21 via the terminal side transmission line 21. Furthermore, if it is abnormal, it is discarded or dummy information is sent.

Next, the detailed operation of cell reproduction in the cell reproduction section 18 will be further explained.

First, since this embodiment employs a sequence number SN and a playback timing number TN having a modulo The rear protection head loading (window size) WS is set.

It is assumed that cells storing user information are generated at a certain period and that the cells are continuously flowing. and,
In the header section where cell control information is stored, a Silkens number SN is added modulo X to ensure the order of the cells.
It is added cyclically. At this time, due to traffic fluctuations, different delay times (fluctuation times) occur for each individual cell. In order to cope with the maximum fluctuation time specified by a certain allowable discard rate, a fluctuation absorption time is set on the cell receiving side. The comparative protection area WS in Figure 2 is
The number of cells is set to match this fluctuation absorption time.

For example, at the timing of the playback timing number TN of the current arriving cell or X, the sequence numbers "0", "]",
. . is lost, and a cell with sequence number "1" arrives with minimal fluctuation and is buffered in the cell receiving section 17. In this case, starting from the value (X) of the current playback timing number TN, the cells with sequence numbers SN within the comparison protection area WS width are returned to the original area in the buffer as subsequent cells, and Sequence number "υ" at playback timing number X
- Received cells of "1" are treated as not to be discarded.

In addition, the comparison protection area WS is set to the playback timing number TN or the playback timing number TN at that time every time the count-up is counted up.
The value is used as a starting point and the comparison protection area WS is shifted to a predetermined width.

In the determination based on the comparison protection area WS, examples of determination taking into consideration the modulo structure are shown in FIGS. 3 and 4.

Figure 3 shows that when TN>SN, TN-rXJ, SN
= Indicates the case where there is a receiving cell of rOJ. In this case, the received cell with the sequence number "0" is not discarded, but is stored again in the same area in the buffer of the cell receiving unit 17 from which it was extracted, and continuity is protected or interpolated at the timing of TN-rXJ. Therefore, a substitute cell called a dummy cell is placed at the playback timing. And the cell of SN-rOJ is
Play at the timing of TN-rOJ.

Similarly, as shown in FIG.
At the time of rlJ, if there is a receiving cell of SN-r2J,
This received cell is stored again in the same area in the buffer of the cell receiving section 17 and reproduced at the timing of TN-"2".

Next, FIGS. 5 and 6 show examples of protection of subsequent received cells.

Playback timing number TN and received cell sequence number S
If cell A to be received was previously taken out at the current playback timing when N does not match, cell A is discarded. Furthermore, if a receiving cell B is connected after cell A in the buffer of the cell receiving section 17, this cell B is taken and the current playback timing number T
Compare with N. If they match, this cell B is reproduced.

In this way, sequence number SN and playback timing number T
By determining the connected cell one stage later when N does not match, it is possible to quickly recover from a continued mismatch state of cell reproduction timing caused by a line clock disconnection or the like. Furthermore, monitoring one stage behind means monitoring several stages behind at the time of judgment, and checking whether there is a match or not.
The intensive processing load is reduced compared to setting

Further, the reproduction processing in the cell reproduction section 18 will be further explained with reference to the cell reproduction timing state transition diagram shown in FIG.

When the reproduction timing number TN and the sequence number SN match, that is, the normal synchronization state 1, the timing shift state 4 occurs due to the mismatch (underrun) between the reproduction timing number TN and the sequence number SN, as shown in FIG. A recovery operation is performed based on the determination shown in FIG. 4, FIG. 5, or FIG. 6.

As a result, if the reproduction timing and the sequence number of the received cell match, the normal synchronization state 1 is restored 3. Further, in this timing shift state 4, a mismatch state monitoring timer (T 2 ) 5 is activated.

CV When the timeout 6 of the timer 5 occurs, it is assumed that the reproduction timing cannot be restored, and a transition is made to the reset state 7. In this reset state 7, the sequence number SN of the most recently received cell is replaced with a new reproduction timing number TN, timing recovery is completed, and the state shifts to normal synchronization state 1.

Further, if a cell overrun 8 occurs from the normal synchronization state 1, the state shifts to the reset state 7 shown above, and the same reset process as described above is executed.

〔Effect of the invention〕

As explained above, according to the present invention, by looking at the cells connected to the rear of the − stage, it is possible to perform early recovery from a mismatched state of playback timing. If the time has elapsed, there is an advantage that the reproduction timing can be restored by replacing the sequence number of the latest received cell with the reproduction timing number.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a cell transmission/regeneration device adopting the cell regeneration control method of the present invention, and FIG. 2 is a diagram showing a set rear protection area (window size).
Figures 3 and 4 are diagrams showing determination examples of this embodiment considering the modulo structure, Figures 5 and 6 are diagrams showing examples of protection of subsequent received cells, and Figure 7 is a diagram showing cell regeneration timing states. FIG. 8 is a diagram showing an example of occurrence of continuous cell discard in conventional cell regeneration. DESCRIPTION OF SYMBOLS 1... Normal synchronization state, 4... Timing shift (recovery operation) state, 7... Reset state, 10... Terminal side receiving line, 11... Terminal interface, 12... Cellization section , 13...Sequence number counter generation unit, 1
4... Cell transmitter, 15... Network side transmission line, 16...
・Network side receiving line, 17... Cell receiving section, 18... Cell reproducing section, 19... Reproducing timing generating section, 2o...
Window size specification section, 21...terminal side transmission line Fig. 2 Fig. 8

Claims (2)

[Claims] (1) In a cell reproduction control method that reproduces a fixed-length data packet by comparing a sequence number indicating a reproduction time series added to a fixed-length data packet with a reproduction timing number updated at a constant cycle on the receiving side, When a discrepancy between the sequence number and the playback timing number occurs, it is monitored whether or not there is a subsequent fixed-length data packet in the currently compared fixed-length data packet, and if there is, this subsequent fixed-length data packet is Compare the sequence number and the current playback timing number,
A cell reproduction control method characterized in that, if a match occurs, the subsequent fixed length data packet is reproduced at the current time. (2) In the cell reproduction control method according to claim (1), if the mismatch between the sequence number and the reproduction timing number continues for a certain period of time or more, the sequence number is changed to the latest one after the certain period of time has elapsed. A cell reproduction control method characterized in that a fixed length data packet is reproduced again after being replaced with a reproduction timing number TN.