JPH09214483A - Bypass retrieval method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To retrieve quickly a bypass on the occurrence of a fault in a transmission line. SOLUTION: A fault of a transmission line TL2 is detected by nodes N3 , N4 , and the node N3 generates a passive token giving a transmission right of a reply signal with respect to a path revision command signal for each of plural paths. The node N4 generates an active token providing an issue right of a path revision command signal to each path and sends the path revision command signal to other transmission lines than the faulty transmission line. The node having a passive token among nodes receiving the path revision command signal generates a reply signal and returns it and switches the set route into a transmission line receiving the path revision command signal. The node receiving the reply signal returns sequentially the reply signal to the transmission line receiving the path revision command signal and when the node N4 receives the reply signal within a prescribed time finally, the route is switched to the transmission line of the reply signal received at first.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a path search method in a network system, and more particularly to a method for automatically searching for a detour and restoring a path when a transmission path failure occurs in the network.

[0002]

2. Description of the Related Art Information and communication networks have become the infrastructure that supports today's social and economic activities.
Therefore, the reliability of the network system is a very important factor. As a countermeasure against transmission line failure, which is one of the communication network failures, a method of searching for a detour and switching lines is adopted, but special technology is required to search for a detour at high speed. , Various methods have been proposed.

Generally, such detour search methods are roughly classified into a centralized control method and a distributed control method. The centralized control method is a method in which a network control center constantly monitors the state of lines and searches for a path that bypasses a failed link when a failure occurs. However, this centralized control method
As the scale of the network increases, the time required for detour search becomes very long, and further, if the network control center itself fails, the detour search function is lost.

On the other hand, the distributed control method has an advantage that the detour can be searched in a short time even if the network becomes large-scale, and the detour can be searched even if a failure occurs in the network control center. Have. As the distributed control method, for example, "a detour path table updating method" disclosed in Japanese Patent Application Laid-Open No. 2-65335 and Japanese Patent Application Laid-Open No. 2-142223.
There is a "network failure recovery method" disclosed in Japanese Patent No.

[0005]

However, in these conventional detour search methods, since a detour path is searched for each link (transmission path), a large bandwidth capacity is searched, and even a detour path search is performed. There was a problem that it took time.

An object of the present invention is to provide an automatic detour route search method capable of executing detour route search at high speed at the occurrence of a failure.

[0007]

In the detour route search method according to the present invention, a failure occurring in a certain transmission line in which a plurality of paths are set is a first node and a second node connected to both ends of the transmission line. Detected by the first node, the first node generates a passive token for giving a right to send a response signal to the path change instruction signal for each of the plurality of paths, and the passive token is transmitted to one of the transmitting and receiving end nodes of the route through the route of each path. By transferring, the passive token is distributed to all the nodes from the first node in the route of each path to one transmitting / receiving end node.

On the other hand, the second node sends the path change instruction signal from the second node to a transmission line other than the transmission line in which the failure is detected by generating an active token for giving the right to issue the path change instruction signal for each path. Then, among the nodes that have received the path change instruction signal, the node having no passive token further sends the path change instruction signal to a transmission path other than the transmission path that has received the path change instruction signal. Further, among the nodes that have received the path change instruction signal, the node having the passive token generates and returns a response signal to the received path change instruction signal, and at the same time transmits the route that has received the path change instruction signal. Switch to the roadside.
The node that receives the response signal sequentially returns the response signals to the transmission path that has received the path change instruction signal, and finally, when the second node receives the response signal within a predetermined time,
The route is switched to the transmission path of the response signal received first. In this way, a new detour is formed.

According to the present invention, a passive token and an active token are generated for each path set in a transmission line in which a failure has occurred, and the passive token is distributed to nodes existing between routes to one transmitting / receiving end node. Then, the node having the active token emits the path change instruction signal to a transmission line other than the faulty transmission line. And
By determining the transmission path from which the response signal to the path change instruction signal has been returned as a detour, the detour can be set in units of paths with a relatively small required bandwidth, and a faster detour search can be performed. It will be possible. In addition, since the passive token is only transferred to each node along the route of the path from the first node to the one transmitting / receiving end node, the amount of information generated in the network for the detour search is limited. The increase can be suppressed.

[0010]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an example of a network system for explaining an embodiment of a detour path search method according to the present invention. Here, for simplification of description, as shown in the figure, they are connected to six nodes N1 to N6 (where N1 to N6 represent node IDs given in advance to the respective nodes). Assume a network system including six transmission lines TL1 to TL6. Further, it is assumed that a failure has occurred in the transmission line TL3 that connects the node N3 and the node N4 when one path Pn from the node N1 to the node N5 is established. The detour path search method according to the present embodiment is executed for each path existing in the transmission line TL3 when the nodes N3 and N4 detect a failure in the transmission line TL3. Here, the path Pn is passed from the node N1 to the node N6. Then, the detour path Pf to the node N5 is set, and the process ends.

FIG. 2 is a schematic block configuration diagram of each node that executes this embodiment. The node according to the present embodiment includes a path detour search processing unit 101 that executes processing such as generation and transmission / reception of various tokens and directives described later, setting of a detour path, and a detour path table that stores a detour path and its required bandwidth. And a processor 1 for controlling operation of the well-known fault detection unit 103, the routing table 104, the network communication circuits 105 and 106, the terminal interface 107, and the entire node.
08.

The tokens used in this embodiment include a passive token PT and an active token AT, and the passive token PT has a right to receive the path change instruction directive PCD and can exist in a plurality of nodes. . Also, active token AT
Is a right to issue the path change instruction directive PCD, and can exist in only one node. More specifically, the node having the active token AT can generate the path change instruction directive PCD, and the node having the passive token can return the response directive RSP to the received path change instruction directive. As shown in FIG. 5, the path change instruction directive PCD includes a path ID field and a bandwidth request field, and the passive token PT, the response directive RSP, and the active token AT each include a path ID field. .

FIG. 3 is a diagram showing generation and transmission / reception of the active token AT, the passive token PT, and the path change instruction directive PCD when a failure is detected. As shown in the figure, when there is a path Pn from the node N1 to the node N5 via the node N3 and a failure occurs in the transmission line TL3 connecting the node N3 and the node N4, The fault detection unit 103 detects the fault occurrence at the nodes N3 and N4 at both ends of the transmission line TL3. Each node detects its own node I when a failure is detected.
D is compared with the node ID at the other end, and if the node ID of its own is small, the passive token PT of the path Pn
When its own node ID is large, the active token AT of the path Pn is generated. Therefore, here, the node N3 uses the passive token PT,
The node N4 generates an active token AT, respectively.

More specifically, the node N3 generates the passive token PT in which the path Pn is written in the path ID,
The routing table 104 is searched to identify the transmission lines TL2 and TL3 in which the path Pn is set, and the transmission line T
The passive token PT is sent to the transmission line TL2 other than L3. The node N2 connected to the transmission line TL2 is the node N
When the passive token PT of the path Pn is received from 3,
Similarly, the transmission paths TL1 and TL2 to which the path Pn is set are specified, and the passive token PT in which the path Pn is written in the path ID is set to the transmission path TL other than the transmission path TL2.
Send to 1. Node N1 connected to transmission line TL1
Even when receiving the passive token PT of the path Pn from the node N2, does not send the passive token because there is no transmission path other than the transmission path TL1 in which the path Pn is set. As a result, here, the passive token exists in the nodes N1 to N3.

On the other hand, in the node N4, when the active token AT of the path Pn is generated, the band of the path Pn is secured in the transmission lines TL4 and TL5 other than the transmission line TL3, and then the path change instruction directive PCD of the path Pn is generated. It is sent to the transmission lines TL4 and TL5. That is, the path change instruction directive PCD1 in which the path Pn is written in the path ID field and the reserved bandwidth is written in the bandwidth request field
And PCD3 are generated, and transmission lines TL4 and TL are generated, respectively.
Send to 5.

The node N6 having received the path change instruction directive PCD1 through the transmission line TL5 stores the transmission line TL5 and the band requested by the path change instruction directive PCD1. Since the node N6 has not received the passive token PT from anywhere, the path change instruction directive PCD2 of the path Pn having the same content is received.
Generate That is, after the bandwidth of the path Pn is secured in the transmission path TL6 other than the transmission path TL5, the path Pn is written in the path ID of the path change instruction directive PCD2, and the secured request bandwidth is written in the bandwidth request, and sent to the transmission path TL6.

Upon receiving the path change instruction directive PCD3 through the transmission line TL4, the node N5 stores the transmission line TL4 and the band requested by the path change instruction directive PCD3. Although the node N5 has not received the passive token PT from anywhere, the path change instruction directive of the path Pn is not transmitted because there is no transmission path in which the path Pn is set.

FIG. 4 is a diagram showing response directive transmission / reception for setting a bypass path. The node N2 that has received the path change instruction directive PCD2 through the transmission line TL6 stores the transmission line TL6 and the band requested by the path change instruction directive PCD2.
Since the node N2 receives the passive token PT from the node N3, the transmission line TL2 which is the route of the path Pn.
PCD2, which is a path change instruction directive received after deleting
The bandwidth written in the bandwidth request field of the transmission line TL
Assign to 6. That is, the node N2 switches the route of the path Pn from the transmission line TL2 to TL6. Then, the response directive RS in which the path Pn is written in the path ID
P1 is returned to the node N6 through the transmission line TL6.

Upon receiving the response directive RSP1 of the path Pn through the transmission line TL6, the node N6 allocates the band required by the path change instruction directive of the same path Pn to the transmission lines TL5 and TL6, and passes it to the path ID of the response directive PCD2. Pn is written and sent to the transmission line TL5. Path Pn through transmission line TL5
Node N4 that received the response directive RSP2 of
Deletes the transmission line TL3, which is the route of the path Pn, and allocates the required bandwidth to the transmission line TL6 that has received the response directive RSP2. That is, the node N4 switches the route of the path Pn from the transmission line TL3 to TL5.

In this way, the node N2 receiving the passive token PT and the node N4 in which the active token AT is present switch the routes, so that the node N
Path Pf from node 1 to node N5 via node N6
The bandwidth required for the above is secured, and the path Pn is changed to the detour path Pf.

Here, if the node N4 having the active token AT does not receive the response directive RSP2 of the path Pn within a fixed time, the node N4 forms a bypass path on the transmission line TL5 which has transmitted the path change instruction directive. Judge that you can't. In this case, node N
Reference numeral 4 sends an active token AT in which the path Pn is written in the path ID to a transmission line (TL4 in this case) other than the transmission line TL3 and the transmission line TL5 in which a failure has occurred, and issues a path change instruction directive to the node N5 here. Transfer the right. Therefore, if the network configuration is such that the node N5 is connected to another node via a transmission path, the node N5 issues the same path change instruction directive as the node N4 and executes the bypass path forming step.

When a node such as the node N6 which receives the path change instruction directive PCD1 does not receive the response directive RSP1 within a fixed time, in order to prevent the bandwidth of the transmission line from being unnecessarily secured, , The bandwidth requested by the path change instruction directive PCD1 and the bandwidth secured when the path change instruction directive PCD2 is transmitted are discarded, and the path change instruction is invalidated.

[Brief description of drawings]

FIG. 1 is a schematic network configuration diagram for explaining an embodiment of a path detour search system according to the present invention.

FIG. 2 is a block diagram of each node for executing this embodiment.

FIG. 3 is a diagram showing generation, transmission and reception of an active token, a passive token, and a path change instruction directive when a failure is detected.

FIG. 4 is a diagram showing response directive transmission / reception for setting a bypass path.

[Explanation of symbols]

 N1 to N6 Nodes TL1 to TL6 Transmission path Pn Normal path Pf Detour path when failure occurs PT Passive token AT active token PCD Path change instruction directive RSP response directive

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[Procedure amendment]

[Submission date] May 7, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Brief description of drawings

[Correction method] Added

[Correction contents]

[Brief description of drawings]

FIG. 1 is a schematic network configuration diagram for explaining an embodiment of a path detour search system according to the present invention.

FIG. 2 is a block diagram of each node for executing this embodiment.

FIG. 3 is a diagram showing generation, transmission and reception of an active token, a passive token, and a path change instruction directive when a failure is detected.

FIG. 4 is a diagram showing response directive transmission / reception for setting a bypass path.

FIG. 5A is a path change instruction used in this embodiment.
It is a schematic signal format diagram of the directive,
(B) is a passive token used in this embodiment,
Answer Directives and active token schematic signals
It is a format diagram.

[Explanation of Codes] N1 to N6 Nodes TL1 to TL6 Transmission Line Pn Path at Normal Time Pf Detour Path at Failure Occurrence PT Passive Token AT Active Token PCD Path Change Directive RSP Response Directive

Claims (3)

[Claims] 1. In a network in which a plurality of nodes are connected in a predetermined form by a plurality of transmission lines, a fault occurring in a certain transmission line in which a plurality of paths are set is connected to both ends of the transmission line. Detected by the first node and the second node, the first node generates a passive token for giving the right to send a response signal to the path change instruction signal for each of the plurality of paths, and the passive token of each path is generated. The passive token is distributed to all the nodes from the first node in the route of each path to the one transmitting / receiving end node by transferring the token through the route to one transmitting / receiving end node of the route, and the second node In the above, an active token that gives the right to issue the path change instruction signal is generated for each of the plurality of paths. Then, the path change instruction signal is sent from the second node to a transmission path other than the transmission path in which a failure is detected, and among the nodes that have received the path change instruction signal, the node in which the passive token does not exist is The path change instruction signal is further transmitted to a transmission path other than the transmission path that has received the path change instruction signal, and among the nodes that have received the path change instruction signal, the node having the passive token is the received path change instruction signal. To the transmission path side that has received the path change instruction signal, the node that has received the response signal is the transmission path that has received the path change instruction signal. The response signal is sequentially returned to the second node, and the second node routes to the transmission path that first receives the response signal within a predetermined time. Setting the detour by switching, detour search method characterized by. 2. When the second node does not receive the response signal within the predetermined time, the active token is transferred to the adjacent node on the other transmission / reception end node side of the route. The detour search method according to claim 1. 3. The two nodes at both ends of the transmission line in which the failure has occurred compare one node with a node identification number that is predetermined in each node, so that one node becomes the first node, 3. The detour search method according to claim 1, wherein the other node is determined as the second node.