JP2677055B2 - Transmission line switching method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in a transmission line switching system of a ring type network.

[0002]

2. Description of the Related Art FIG. 3 shows a frame format of a main signal of a transmission path switching system. FIG. 4 is a block diagram of a conventional transmission path switching system. FIG. 5 is a diagram showing a switching operation of a transmission path switching system of a conventional example.

Conventionally, in the transmission path switching system, each node forming a ring transmits / receives the switching control overhead 30 in the main signal frame shown in FIG. 3 between adjacent nodes, and each node performs loopback, through, etc. The function of the entire ring was restored by connecting the transmission line. When a transmission line failure occurs, the contents of the switching control overhead 30 being transmitted and the transmission line connection state of the own station node are changed according to the transmission line switching request type and the contents of the switching control overhead 30 being received. Since it is necessary to perform extremely complicated processing such as, each node generally implements these processing by software.

As a conventional example, consider a ring network in which adjacent nodes are connected by two transmission lines, a working system and a standby system. FIG. 4 and FIG. 5 show an example of transmission line switching of the ring type network configured by this node.

FIG. 4 shows the switching control information transmitted by each node and the main signal connection state in each node in a normal state without a transmission line failure. In FIG. 4, reference numerals 1 to 4 denote nodes that form a ring, and 11 and 12 respectively indicate a clockwise transmission path and a counterclockwise transmission path. Of the nodes, the node 1 is the master node, and normally, as shown in FIG. 4, the master node 1 has “No switching (No Requests).
t, hereinafter referred to as NR. ), No switching request destination (master node ID number), no switching request source (master node ID number) ”is sent to the bidirectional transmission path, and no switching request Slave nodes 2 to 2 are connected so that the signal that receives the main signal is transmitted as it is without changing its direction (hereinafter referred to as "through connection").
No. 4 determines that the received no switching request (NR, 1, 1) is not a switching request to the own node, and sends the received no switching request content to the downstream adjacent node as it is,
Make a "through connection" for the main signal in your station.

A transmission line switching operation when a transmission line disconnection fault occurs in the counterclockwise transmission line 11 which is the active system shown in FIG. 5 is shown. First, when the slave node 2 detects the failure 21, the master node 1 is designated as the switching request destination to the downstream adjacent slave node 3 and the signal interruption (Signal Fail) is performed.
1, hereinafter referred to as SF. ) Switching request (SF, 1,
2) is sent. The slave node 3 that has received this switching request (SF, 1, 2) determines that the switching request is not a switching request for its own node, and receives the switching request (SF,
The contents of 1, 2) are directly applied to the adjacent slave node 4 on the downstream side.
And the main signal in the local station is left as "through connection". Similarly, the slave node 4 also sends the contents of the switching request received from the upstream to the master node 1 and keeps the main signal "through connection". In the master node 1, since the received switching request (SF, 1, 2) is a switching request for its own node, a connection for sending back the received signal of the main signal connection in its own station (hereinafter referred to as “loopback connection”). ".).

Further, in the master node 1, as a response to the switching request (SF, 1, 2), the slave node 2 is designated as the switching request destination, and the switching response request (Reverse).
Request, hereinafter referred to as RR. ) (RR, 2,
1) is transmitted to the slave node 4 in the counterclockwise direction. Regarding the exchange of overhead in the counterclockwise direction, even if the slave nodes 4 and 3 receive this switching response request (RR2, 1), it is not a switching request to the own node, so the received switching response request (RR2, 1) is received. ) Is sent to the downstream node, and the main signal in the local station remains "through connection". In the slave node 2, since this switching response request (RR, 2, 1) is a switching request to its own node, the main signal in its own station is “looped back”.

[0008] As described above, the transmission path switching of the ring type network is started by first sending the switching request to the downstream node, which designates the upstream node having the transmission path disconnection as the switching request destination. There are spliced sequentially <br/> in between adjacent nodes. When the switching request reaches the switching request destination node, the loopback connection of the transmission line is performed at this node.

Further, the switching request destination node returns a switching response to the switching request transmitting node via the reverse route of the switching request transmitting route, and the switching request transmitting node receiving the switching response "connects the selector in its own station" to "loopback connection". To do. When this series of operations is completed, each node can reconfigure the ring and provide normal service again.

[0010]

However, in such a conventional transmission line switching system, since each node constitutes a ring, the transmission line is relieved when a failure occurs such that the ring is cut off. In this case, it is necessary to exchange the switching control information between the fault detection node and the opposite node across the fault occurrence route via a route having a longer total length than the fault route. For this reason, when the number of all nodes in the ring increases, the number of times of software control required to relay the switching control information increases, and generally, the switching time from the occurrence of a failure to the reconfiguration of the ring becomes long, There was a drawback that the time until the service was restored increased.

The present invention solves the above-mentioned drawbacks by enabling the switching control overhead to be exchanged at high speed, and shortening the switching time from the occurrence of a failure to the reconfiguration of the ring, so that service can be provided. It is an object of the present invention to provide a transmission line switching method that can reduce the time until restoration.

[0012]

SUMMARY OF THE INVENTION The present invention comprises a plurality of nodes connected to a ring network consisting of two transmission lines of a working system and a standby system, and the two transmission lines have mutually different directions. Includes switching control information of each node above
The main signal to which the overhead is added is transferred, and each of the nodes transmits the received main signal without changing the direction, and the received main signal based on the content of the switching control information added to the main signal. In the transmission path switching system including a means for returning and transmitting the received transmission control information, each of the nodes receives the received switching control information based on the contents of the received overhead switching control information or the failure state of the transmission path to be transmitted.
It is characterized by including a means for selecting whether to directly transmit the overhead including the above or to set and transmit the overhead at the own node.

Further, according to the present invention, the switching control information may include a type of switching request, a switching request destination node identification number, and a switching request source node identification number.

Further, according to the present invention, the types of the switching request may include no switching request, switching request, and switching response request.

[0015]

According to the contents of the received switching control information or the failure state of the transmission path to be transmitted, each node selects whether to transmit the received switching control information as it is or to newly set and transmit it at its own node.

As described above, the switching control overhead can be exchanged at high speed, and the switching time from the occurrence of a failure to the reconfiguration of the ring can be shortened to shorten the time until the service is restored.

[0017]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a transmission line switching system according to an embodiment of the present invention.

In FIG. 1, the transmission line switching system is a clockwise transmission line 11 as two transmission lines of an active system and a standby system.
And a master node 1 and slave nodes 2 to 4 as a plurality of nodes connected to the ring network composed of the counterclockwise transmission line 12 and the clockwise transmission line 11
The main signal to which the switching control information of the master node 1 and the slave nodes 2 to 4 is added is transferred to the counterclockwise transmission line 12 in different directions, and the master node 1 and the slave nodes 2 to 4 receive the received main signal. It includes means for transmitting the signal as it is without changing its direction, and means for returning the received main signal based on the content of the switching control information added to the main signal and transmitting it.

The feature of the present invention is that the master node 1 and the slave nodes 2 to 4 send the received switching control information as it is based on the contents of the received switching control information or the fault condition of the transmission path to be transmitted. It is to include a means for selecting whether to perform or set a new transmission at the own node.

Further, the switching control information includes the type of switching request, the switching request destination node identification number, and the switching request source node identification number.

Further, the types of switching request include no switching request, switching request, and switching response request.

The operation of the transmission path switching system having such a configuration will be described. FIG. 2 is a diagram showing a switching operation of the transmission path switching system of the present invention.

In FIG. 1, the master node 1 sends the switching control information (NR, 1, 1) to a bidirectional transmission path, and keeps the main signal of its own node "through connection". (The overhead transmission selection is the local selection.). Normally, the slave nodes 2 to 4 select the overhead received from the transmission path and “through connect” the overhead. Further, the switching control unit constantly monitors only the overhead of receiving in both directions, and does not set it.

In FIG. 2, when a transmission line disconnection fault occurs in the transmission line 11 that is the active system, when the slave node 2 detects the fault 12, the slave node 2 sends the master node 1 to the downstream slave node 3 as the switching request destination. Request to switch (S
F, 1, 2) is transmitted (the overhead transmission selection of the slave node 2 is set to its own station). The slave nodes 3 and 4 that have received this switching request remain "through connection" for both the main signal connection and the overhead connection because the switching request is not a switching request for the own node. In the master node 1, since the received switching request (SF, 1, 2) is a switching request for its own node, the selector in its own station “loops back”.

Further, in the master node 1, as a response to the SF switching request (SF1, 2), the slave node 2 is designated as the switching request destination and the switching response request (RR, 2,
1) is transmitted (the overhead transmission selection of the slave node 2 is set to its own station). Then slave node 4,
In No. 3, even if this switching response request (RR2, 1) is received, since it is not a switching request to the own node, both the main signal and the overhead remain "through connection". In the slave node 2, since the switching response request (RR, 2, 1) is a switching request for its own node, the main signal selector in its own station is “looped back”.

As described above, the transmission path switching is started by sending the switching request to the downstream node, which specifies the upstream node which has the transmission path disconnection as the switching request destination, and the switching request is transmitted between the adjacent nodes. Will be relayed in sequence. When the switching request reaches the switching request destination node, the loopback connection of the transmission line is performed at this node. Further, the switching request destination node returns a switching response to the switching request transmission node via the reverse route of the switching request transmission route, and the switching request transmission node receiving the switching response "loops back" the selector in its own station. When this series of operations is completed, each node can reconfigure the ring and provide normal service again.

As described above, in the present embodiment, when the switching control overhead received by each node is not a switching request or a switching response request to the own node, or when the transmission path to be sent is normal, the switching control overhead is downstream. Since it is not necessary to perform the process of "through connection" for setting, the request can be transmitted to the request destination in a short time, and the switching time from the occurrence of the failure to the reconfiguration of the ring can be shortened.

[0028]

As described above, according to the present invention, the switching control overhead can be exchanged at high speed, and the switching time from the occurrence of a failure to the reconfiguration of the ring can be shortened so that the service can be provided. It has an excellent effect of reducing the time required for restoration.

[Brief description of the drawings]

FIG. 1 is a block configuration diagram of a transmission path switching system according to an embodiment of the present invention.

FIG. 2 is a diagram showing a switching operation of the transmission path switching system of the present invention.

FIG. 3 is a frame format of a main signal of a transmission path switching system.

FIG. 4 is a block configuration diagram of a conventional transmission path switching system.

FIG. 5 is a diagram showing a switching operation of a conventional transmission path switching system.

[Explanation of symbols]

 1 master node 2 to 4 slave node 30 switching control overhead 31 type of switching request 32 switching request destination node identification number 33 switching request source node identification number (NR1, 1) no switching request (RR2, 1) switching response Request (SF, 1, 2) Switch request

Claims (3)

(57) [Claims] 1. A plurality of nodes connected to a ring network composed of two transmission lines of an active system and a standby system, wherein the two transmission lines have switching control information of each node in different directions. The main signal to which the overhead is added is transmitted, and each of the above nodes receives the main signal without changing the direction and receives it based on the content of the switching control information added to the main signal. In the transmission path switching method including means for returning and transmitting the main signal, each of the above-mentioned nodes includes the overhead including the received switching control information based on the content of the received switching control information of the overhead or the failure state of the transmission path to be transmitted. a transmission path switching system characterized in that it comprises a means for selecting whether to transmit the set newly as is its own node to send. 2. The transmission path switching system according to claim 1, wherein the switching control information includes a switching request type, a switching request destination node identification number, and a switching request source node identification number. 3. The transmission line switching system according to claim 2, wherein the types of the switching request include no switching request, a switching request, and a switching response request.