JPH1065685A - Continuity check cell monitor circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect an abnormal state that a CC cell is not received although an idle cell exists during cell flow and the CC cell is in a transmission possible state on a reception side in a CC(continuity check) cell monitor circuit. SOLUTION: In the CC cell monitor circuit which is one of the OAM functions of an ATM transmission system and which outputs an LOC(loss of continuity) fault signal when a user cell or the CC cell which is periodically inserted is not received in a received cell flow for a prescribed time, the received cell judgment circuit 8 of the reception side detects the user cell, the CC cell and the idle cell. An abnormal state monitor circuit 14 monitors a state where the CC cell is not received although the idle cell is received, and output the abnormal state when the abnormal state continues for a prescribed time. The abnormal state monitor circuit 14 comprises a reception judgment circuit judging the reception of the idle cell and the CC cell, an abnormal state monitor timer monitoring the reception state of the CC cell and the abnormal state output circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an OAM function in an ATM transmission system, and more particularly, to a continuity check (hereinafter referred to as "CC") function, which is one of the OAM functions, in which a CC cell is inserted into a cell flow at a constant period. The present invention relates to a CC cell monitoring circuit that monitors continuity.

[0002]

2. Description of the Related Art Conventionally, this type of CC cell monitoring circuit includes a transmitting side 1 and a receiving side 2 as shown in FIG. It monitors continuity.

[0003] A transmitting side 1 transmits one cell per second to a vacant cell position of a received cell flow, in order to transmit a CC cell,
The empty cell detection circuit 3 detects an empty cell position from the received cell flow, and the transmission interval timer 4 generates an interval for transmitting CC cells. Further, the transmission side 1 generates a transmission control signal by the transmission determination circuit 5. When transmitting the CC cell to the cell flow, the transmitting side 1 generates the CC cell by the CC cell generation circuit 6 and transmits the CC cell by the CC cell transmission circuit 7 using the transmission control signal generated by the transmission determination circuit 5.

[0004] When the receiving side 2 does not receive a user cell or a CC cell within 3.5 seconds and 0.5 seconds,
In order to generate a LOC (Loss Of Continuity) failure, the reception cell determination circuit 8 determines a user cell and a CC cell, and receives a user cell reception signal 9 when a user cell is received and a CC when a CC cell is received. The cell reception signal 10 is output, and continuity is monitored by the continuity monitoring timer 11.

The operation of the continuity monitoring timer 11 is shown in FIG.
As shown in (A), when a user cell or a CC cell exists in the received cell flow, the received cell determination circuit 8 outputs a user cell received signal 9 or a CC cell received signal 10.
Is output, the continuity monitoring timer 11 is cleared. However, as shown in FIG.
When there is no C cell, the continuity monitoring timer 11 keeps counting, and when 3.5 seconds and 0.5 seconds have elapsed, the continuity monitoring timer 11 goes low.
An OC fault 12 is output.

[0006]

In the conventional CC cell monitoring circuit, the continuity monitoring timer is cleared when either the user cell or the CC cell is received on the receiving side.
Even if the CC cell is not received, if only the user cell is received, the LOC state is not set. That is, FIG.
As shown in (C), there is a problem that the receiving side does not monitor an abnormal state in which a CC cell is not detected even though an empty cell exists in the cell flow and the CC cell can be transmitted. was there.

[0007] It is an object of the present invention to monitor an abnormal state in which a CC cell is not received on a receiving side, even though an empty cell exists in a cell flow and a CC cell can be transmitted. An object of the present invention is to provide a more accurate CC cell monitoring circuit which can determine whether an abnormality or insertion state of a circuit on a transmitting side of a cell can be performed.

[0008]

The CC cell monitoring circuit according to the present invention is one of the OAM functions of the ATM transmission system, in which a user cell or a CC cell inserted at a fixed period in a reception cell flow is not received. On the receiving side of the CC cell monitoring circuit that outputs a continuity failure signal in the case of
An abnormal state monitoring means for outputting an abnormal state signal when a state in which an empty cell is received and a state in which the CC cell is not received continues for a predetermined time is provided.

The abnormal state monitoring means receives an empty cell reception signal or a reception signal of a CC cell, determines the presence of the empty cell or the CC cell, and outputs the reception signal. An abnormal state monitoring timer that clears the timer and monitors the reception state of the CC cell;
An abnormal state output means for detecting an output of the reception determining means and an output of the abnormal state monitoring timer after a lapse of a predetermined time after the timer is not cleared, and outputting an abnormal state signal.

In the CC cell monitoring circuit of the present invention, when a receiving cell is detected on the receiving side, an empty cell can be detected in addition to detecting a user cell and a CC cell.

[0011] Furthermore, although there is an empty cell in the cell flow and CC cells can be transmitted,
An abnormal state monitoring circuit that monitors an abnormal state that the C cell is not received is provided.

The receiving side of the CC cell inconsistency monitoring circuit detects a user cell, a CC cell and an empty cell from the received cell flow, and the abnormal state monitoring circuit is receiving an empty cell. Monitor the status of receiving no. When 3.5 seconds 0.5 seconds have passed in this state, it is output as an abnormal state.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention will be described in detail with reference to FIGS.

On the transmitting side 1, an empty cell detecting circuit 3 detects an empty cell position from the received cell flow and sends a CC cell to the empty cell position of the received cell flow. 4, CC
Generate intervals for sending cells. Further, the transmission determination circuit 5
Generates a transmission control signal. When transmitting a CC cell to the cell flow, the CC cell is generated by the CC cell generation circuit 6 and transmitted by the CC cell transmission circuit 7 using the transmission control signal generated by the transmission determination circuit 5.

On the receiving side 2, a user cell, a CC cell and an empty cell are detected by a reception cell judgment circuit 8, and when a user cell is received, a user cell reception signal 9 is received and a CC cell is received. Time is CC cell reception signal 1
0 is output, and an empty cell reception signal 13 is output when an empty cell is detected. The continuity monitoring timer 11 monitors the reception state of the user cell and the CC cell from the output result of the reception cell determination circuit 8.

Further, an abnormal state monitoring circuit 14 is provided for monitoring a state in which an empty cell is received but no CC cell is received. The abnormal state monitoring circuit 14
It comprises a reception judgment circuit 141 for judging the reception of an empty cell and a CC cell, an abnormal state monitoring timer 142 for monitoring the reception state of the CC cell, and an abnormal state output circuit 143.

Next, the operation of the embodiment of the present invention will be described with reference to FIG.

On the transmitting side 1, as shown in FIG. 3A, a transmission interval of a CC cell is generated by a transmission interval timer 4 in order to transmit one CC cell per second. When one second has elapsed from the transmission interval timer 4, the empty cell detection circuit 3
When an empty cell is detected, the CC cell generated by the CC cell generation circuit 6 is transmitted from the CC cell transmission circuit 7. When a cell other than a vacant cell is detected by the vacant cell detection circuit 3, the CC cell transmission processing is not performed.

Also, when the transmission interval timer 4 has not elapsed for one second, no CC cell is transmitted.

On the receiving side 2, the receiving cell judgment circuit 8
Is used to judge the reception cell. When a user cell is detected, a user cell reception signal 9 is received. When a CC cell is received, C
When a C cell reception signal 10 is received and an empty cell is received, an empty cell reception signal 13 is output.

When a user cell is received, the cell shown in FIG.
As shown in (1), the continuity monitoring timer 11 is cleared.

When a CC cell is received, the inconsistency monitoring timer 11 is cleared and the reception determination circuit 141 of the abnormal state monitoring circuit 14 clears the C as shown in 2 of FIG.
The C cell reception is output, and the abnormal state monitoring timer 142 is cleared.

When an empty cell is received, the continuity monitoring timer 11 outputs the LOC failure 12 when 3.5 Saturdays and 0.5 seconds have elapsed, as shown at 3 in FIG. 3B. I do. Further, the reception determination circuit 141 of the abnormal state monitoring circuit 14
When the abnormal state monitoring timer 142 has passed 3.5 ± 0.5 seconds, the abnormal state output circuit 143 outputs the abnormal state 15.

If another cell is received,
As shown in 4 of (B), the continuity monitoring timer 11
When 3.5 seconds have elapsed 0.5 seconds, LOC failure 12 is output.

[0025]

Next, an embodiment of the present invention will be described with reference to FIG.

In order to transmit one cell per second to the empty cell position of the received cell flow on the transmitting side 1, the empty cell detection circuit 3 detects the empty cell position from the received cell flow and sends the CC cell to the empty cell position. 4, CC
Generate intervals for sending cells. Further, the transmission determination circuit 5
, A transmission control signal is generated, and the CC cell transmission circuit 7 inserts a CC cell into a vacant cell position and transmits it.

In the receiving side 2, when the received cell flow is normal, as shown in FIG. 4 (A), the receiving cell determination circuit 8 detects a user cell or a CC cell, and the continuity monitoring timer 11 clears. Is done. Further, the detection of the CC cell clears the abnormal state monitoring timer 142.

When neither the user cell nor the CC cell exists in the received cell flow, the continuity monitoring timer is cleared because neither the user cell nor the CC cell is detected by the reception cell determination circuit 8 as shown in FIG. 3.5 3.5
After a lapse of seconds, LOC failure 12 is output.

If there is no CC cell in the received cell flow even though there is a free cell, the received cell determination circuit 8 detects a free cell and a user cell as shown in FIG. 4C. Since the continuity monitoring timer 11 is cleared by detecting the user cell, the LOC
Although no failure occurs, the abnormal state monitoring timer 142 of the abnormal state monitoring circuit 14 is not cleared because no CC cell has been received. Is received, the abnormal state output circuit 143 outputs the abnormal state 15.

[0030]

As described above, the CC cell monitoring circuit of the present invention can detect an abnormal state in which the receiving side receives an empty cell but does not receive a CC cell. It is possible to determine the abnormality of the circuit on the transmission side of the CC cell or the reception state by observing this state, and it is possible to perform monitoring with higher accuracy.

[Brief description of the drawings]

FIG. 1 is a diagram showing a circuit configuration of an embodiment of the present invention.

FIG. 2 is a diagram showing a circuit configuration of an abnormal state monitoring unit in FIG.

FIG. 3 is a flowchart showing the operation of one embodiment of the present invention. (A) is a flowchart on the transmitting side, and (B) is a flowchart on the receiving side.

FIG. 4 is a diagram showing a reception cell flow for explaining the operation of one embodiment of the present invention. (A) is in the normal state,
FIG. 6B is a diagram illustrating a received cell flow when an LOC failure occurs, and FIG. 7C illustrates a received cell flow when an abnormal state occurs (an empty cell exists but a CC cell does not exist).

FIG. 5 is a diagram showing an example of a conventional CC cell monitoring circuit.

FIG. 6 is a diagram showing a reception cell flow for explaining the operation of the conventional CC cell monitoring circuit. (A) is a diagram showing a received cell flow in the case of a normal state, (B) is a case of a LOC failure, and (C) is a diagram of a received cell flow in a case of an abnormal state (an empty cell exists but no CC cell exists). It is.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 transmission side 2 reception side 3 empty cell detection circuit 4 transmission interval timer 5 transmission determination circuit 6 CC cell generation circuit 7 CC cell transmission circuit 8 reception cell determination circuit 9 user cell reception signal 10 CC cell reception signal 11 continuity monitoring timer 12 LOC failure 13 Empty cell reception signal 14 Abnormal state monitoring circuit 15 Abnormal state 141 Reception judgment circuit 142 Abnormal state monitoring timer 143 Abnormal state output circuit

Claims (2)

[Claims] An OAM function of the ATM transmission system, which is a LOC failure signal with a lack of continuity when a user cell or a continuity check cell inserted at a constant period is not received in a received cell flow. On the receiving side of the continuity check cell monitoring circuit that outputs a signal, an abnormal state signal is output when a state in which the continuity check cell is not received continues for a predetermined time while an empty cell is being received. A continuity check cell monitoring circuit comprising an abnormal state monitoring means. 2. A reception judging means for receiving an empty cell reception signal or a continuity check cell reception signal, judging the existence of the empty cell or continuity check cell, and outputting the same. An abnormal state monitoring timer that clears a timer by a reception signal of the continuity check cell and monitors the reception state of the continuity check cell; an output of the reception determination unit; 2. The continuity check cell monitoring circuit according to claim 1, further comprising an abnormal state output unit that detects an output of the abnormal state monitoring timer and outputs an abnormal state signal.