JPS61292438A - Loopback control system - Google Patents

Abstract

PURPOSE:To quicken the recovery of a communication system by providing a means detecting that the reception signal of one transmission system is normal and the reception signal of other transmission line system is not normal and using a changeover means to set the branch of the signal. CONSTITUTION:A loopback control section 40 inputs the detection signal of frame synchronizing detection circuits 4, 14 and controls switches 5, 15, 21 so as to branch a signal received from a normal system to the transmission side of the abnormal system when the state that only one transmission line system is normal continues for a prescribed time. That is, the loopback control section 40 discriminates that the state that a synchronizing detection signal is received from, e.g., the circuit 4 and no synchronizing detection signal is obtained from the circuit 14 continues for a prescribed time, the section 40 constitutes the loopback from the system 0 to the system 1 by setting the switches 5, 15 to the position R and the switch 21 to the position L.

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] This is a loopback control method in a communication system using a duplicated circular transmission line. Each node is equipped with a function to configure a loopback to monitor the received signal and, if only one transmission line system continues to be in a normal state, branch this signal to the other system, and release the loopback. By performing this in accordance with a command from a monitoring node, the range of the loop by loopback can be automatically expanded as recovery from a failure or the like occurs.

[Industrial application field]

The present invention relates to a loop bank control method in a communication system having a duplicated ring transmission path.

In a communication system using a circular transmission line, the transmission line has a duplex configuration with two systems of circular transmission lines in opposite transmission directions, and when a failure or power outage occurs that makes it impossible for both systems to transmit in a certain section. A technique that enables communication in the section excluding the faulty section by configuring one loop with the transmission paths of both systems excluding the faulty section is well known as a loop bank.

In such a communication system, when a failure or the like occurs, the configuration of the loop bank makes it possible to quickly communicate in a section other than the failed section, and after that, the section from which the failure has been recovered becomes a communicable loop bank loop. It is hoped that it will be incorporated quickly.

[Prior Art and Problems to be Solved by the Invention] FIG. 3(a) is a block diagram of a configuration example of a communication system having a duplicated ring transmission path.

In the system, for example, one monitoring node 31 and a plurality of nodes 32 are connected by an O-system transmission line system 33-O and a 1-system transmission line system 33-1.

Each node 32 is a node for accommodating required terminal lines and controlling communication between terminal lines in this communication system, and the monitoring node 31 is a node for monitoring/controlling the state of the system. .

FIG. 2 is a block diagram of a configuration example of each notebook 32. As shown in FIG.

In the figure, 1 and 11 are transmitting/receiving units for the O-system and I-system transmission lines, respectively.

For example, in the 0 system, the signal on the transmission path is received by the receiving circuit 2, the received signal is monitored by the frame synchronization detection circuit 4, and is sent to the control unit 22 via the switch 5, the transmitting circuit 3, and the switch 21. be transferred. The transmission signal is sent from the transmission circuit 3 to the transmission path.

■As for the system, the receiving circuit 12 that constitutes the transmitting/receiving section 11
, the frame synchronization detection circuit 14, the switch 15, and the transmission circuit 13 constitute a connection similar to that of the transmission/reception section l.

When the system is operating normally, for example, the received signal on the 0-system transmission line is transmitted from the receiving circuit 2 to the switch 21.
The signal is input to the control section 22 via the L side of the signal.

The control unit 22 performs necessary processing, such as data exchange with the terminal line support unit 23 connected to itself and communication processing with the monitoring node 31, on the data sequentially received in the communication frames, and performs necessary processing such as communication processing with the monitoring node 31. side, the transmission circuit 3 and then relayed sequentially to the 0-system transmission path.

It is assumed that the communication frame has a certain format as shown in FIG. 4, for example, and that the monitoring node 31 generates a communication frame according to this format and sends it to the transmission paths of both systems.

In the frame format shown in FIG. 4, Fll is a frame header consisting of a specific bit pattern indicating frame division, DLC is a control information section exchanged between the monitoring node 31 and other nodes 32, and TS 1 , TS 2- is a time slot assigned to each terminal line and used to transfer transmission/reception data of the terminal line.

The signal received by the receiving circuit 12 from the 1-system transmission path is directly relayed to the 1-system transmission path through the L side of the switch 15 and the transmitting circuit 13. Namely 1. In this state, the 0 system is the active system used for actual communication, and the 1 system is the so-called standby system in a bypass state.

The monitoring node 31 monitors the received signals of both systems, for example, θ
A state in which frame synchronization cannot be achieved is detected in the system signal,
(2) If the system is normal, the DLC is used to instruct all nodes 32 to use the 1 system as the current system, and each node 32 switches the 1 system to the current state and the θ system to the bypass state.

In addition, if the monitoring node 31 detects an abnormality in the received signals of both systems, for example, for all the swords 32, it simultaneously configures a loopback from the currently selected system to the opposite system. The command of the loop bank is changed to the DLC of the frames of both systems.
and send it out.

Each node 32 selects one system that can normally receive the frame and receives the frame, and the node 32 that has selected the 0 system relays the received signal of the O system according to the command by the control unit 22 and switches The signals are sent from the R side of the switch 15 to the transmitting circuit 3, and are also branched to the l-system transmission line via the R side of the switch 15 and the transmitting circuit 13, thereby controlling each switch so as to form a loopback.

Also, the node 32 that has selected the ■ system, contrary to the above,
A loop bank from the 1st system to the O system is configured so that the received signal of the 1st system is relayed by the control unit 22 and transmitted to both systems.

Thereafter, the monitoring node 31 issues a designated command to cancel the loopback only to the node 32 for which the signals of both systems are normal.

Once each node 32 configures a loopback, if it can successfully receive signals from both systems and synchronization is achieved in the frame synchronization detection circuits 4 and 14, it configures a loopback from the O system to the 1 system, for example. The loopback is canceled by controlling the switch 15 of the 1st system, and the normal connection that bypasses the 1st system is restored.

As a result, as shown in FIG.
4. If there is an abnormality such as a power outage in node 35,
and the loop bank at node 36 remains, thus realizing a loopback configuration connecting each node from node 37 to node 36 via monitoring node 31.

The monitoring node 31 uses the DLC of the frame to constantly call each node 32 in sequence at an appropriate cycle and request status information. In response, each node 32 notifies the monitoring node 31 of the signal reception status of both transmission lines using DLC.

In the state where the loop bank loop is configured as described above, the monitoring node 31 receives a notification that the reception status of the nodes 36 and 37 at the end of the loopback loop is normal in both systems. , node 34.
35 is detected, the monitoring node 31 instructs the nodes 36 and 37 to release the loop bank, thereby restoring the two-system circular transmission line configuration as shown in FIG. 3(a).

According to the conventional method described above, there is a problem in that the loopback is not canceled until the recovery of the entire failed section is detected by the monitoring node 31, and until then, the operation is limited to the first loopback loop.

[Means for solving problems]

FIG. 1 is a block diagram showing the configuration of one node of the present invention.

In the figure, 40 indicates a loopback control unit that controls automatic loopback.

[For production]

The loopback control unit 40 inputs the detection signals of the frame synchronization detection circuits 4 and 14, and when only one transmission line system is in a normal state for a predetermined period of time, the loopback control unit 40 transfers the signal received from the normal system to the abnormal system. Switch 5 to branch to the sending side.
15.21 control.

For example, when the node 34 recovers and starts operating in a state where a loopback loop as shown in FIG. As a result of successful reception, node 34
Then, the loopback control unit 40 sets a loopback from the O system to the 1 system transmission line. Therefore, the signal sent to the 0-system transmission line 41 at the node 36 is relayed at the node 34 and banked to the 1-system transmission line 42.

When the monitoring node 31 detects this state by adjusting to the node 36, it instructs the node 36 to cancel the loopback setting, and when the node 36 releases the loopback, the end of the loop bank loop is transferred from the node 36 to the node 36. Automatically expands to 34.

In this way, the loop is automatically and sequentially extended to the node adjacent to the end of the loop bank loop each time the node recovers, thereby speeding up the recovery of the communication system.

〔Example〕

It is assumed that each part in FIG. 1 operates in the same manner as in the conventional case, and the switches 5, 15, and 21 operate as in the conventional case.
Normally, the control unit 22 performs control in accordance with commands from the monitoring node 31 to configure specified connections for active/protection switching of the 0-system and 1-system transmission lines and for loop bank configuration.

The loop bank control unit 40 inputs the detection signals of the frame synchronization detection circuits 4 and 14, and when only one transmission line system is in a normal state for a predetermined period of time, the loop bank control unit 40 transfers the signal received from the normal system to the abnormal system. Switch 5 to branch to the sending side.
15.21 control.

That is, when the loopback control unit 40 receives a synchronization detection signal from the frame synchronization detection circuit 4 and identifies that a state in which a synchronization detection signal cannot be obtained from the frame synchronization detection circuit 14 has continued for a certain period of time, the loopback control unit 40 switches the switch 5. By setting the switch 15 to the R side and the switch 21 to the L side, a loopback from the 0 system to the 1 system is configured.

In addition, in a state where the synchronization detection signal is not obtained from the frame synchronization detection circuit 4 and the synchronization detection signal is received from the frame synchronization detection circuit 14, the switches 5, 15, and 21 are set to the opposite side from the above, Configure a loopback from system 1 to system O.

Assume that the communication system is in a state where the nodes 34 and 35 have failed and the illustrated loopback loop has been created, for example, as shown in FIG. 3(b).

Now, when the faulty node 34 recovers and becomes operational, the node 34 normally receives only the signal from the 0-system transmission line 41 sent from the node 36, and as a result, the node 34
The above function of the loop bank control unit 40 sets a loopback from the 0 system to the 1 system transmission line.

Therefore, the signal sent to the O-system transmission line 41 by the node 36 is relayed by the node 34, and then packed to the 1-system transmission line 42, and frame synchronization is detected at the node 36 with the received signal from the 1-system transmission line 42. .

In this way, when the monitoring node 31 detects, by periodically adjusting to the node 36, that the reception state of the node 36 has changed from the state where only the 0 system is synchronized to the state where both systems are synchronized. , if necessary, identifies a required condition, such as that other states within the system have not changed, and instructs the node 36 to cancel the loopback setting using the DLC of the communication frame.

This command causes the control section 22 of the node 36 to
By resetting 5 and breaking the loopback, the end of the loop bank loop is automatically extended from node 36 to node 34.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, in a communication system using a redundant circular transmission line, each time a node, etc. outside the loopback loop recovers, the loop is automatically extended sequentially to that node. This has the significant industrial effect of improving system availability by speeding up the recovery of the communication system.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a block diagram of a conventional configuration example, FIG. 3 is an explanatory diagram of the configuration of a communication system, and FIG. 4 is an explanatory diagram of a communication frame format. In the figure, l and ll are transmitting/receiving units, 2.12 is a receiving circuit, and 3.
13 is a transmitting circuit, 4.14 is a frame synchronization detection circuit, 5.15.21 is a switch, 22 is a control unit, 23 is a terminal line support unit, 31 is a monitoring node, 32.34.35.
36.37 is a node, 33-0 is a θ system transmission line system, 33
-1 indicates the transmission line system of the 1st system, and 40 indicates the loopback control section.

Claims (1)

[Scope of Claims] A communication system having two systems of circular data transmission paths in which at least one monitoring node and a plurality of nodes are successively connected through two transmission paths in opposite directions, each node comprising: Switching means (5, 15, 2) for branching the signal sent to one transmission line system and sending it to the other transmission line system.
1) Means (40) for detecting a state in which the reception signal of one of the transmission line systems is normal and the reception signal of the other transmission line system is not normal, and setting signal branching by the switching means. , and means (22, 40) for receiving the command from the monitoring node and canceling the setting of the signal branch by the switching means.
A loopback control method characterized by having: