JPH03192933A - Bypass path retrieving system - Google Patents

Abstract

PURPOSE:To allow this system to cope with even a node fault by using a node from which a bypass path setting message is returned as the other end point of the bypass path and deciding a node from which the bypass path retrieving message passes as a node forming the bypass path. CONSTITUTION:Each node in a network is provided with a path tracer generating means 1, a path tracer storage means 2, a bypass path retrieval message transmission means 3, a bypass path setting message return means 4, a bypass path retrieval message relay means 5 and a bypass path setting message relay means 6. Then a node through which the bypass path setting message is returned is used as the other end point of the bypass path and a node through which the bypass path retrieving message passes is decided as a node forming a bypass path. Thus, the system copes with a fault of nodes.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to a method for searching for a detour path when a node or link fails in a network, and an object of the present invention is to provide a detour path search method that can cope with a node failure. In each node of the network that searches for a detour path due to flooding, a path tracer generation means for generating a path tracer, a path tracer storage means for storing the path tracer, and a message regarding node candidates for the detour path are sent. A detour path search message sending means for broadcasting to each section overhead, a detour path setting message return means for sending a detour path setting message to the section overhead when the node corresponds to a candidate node for the detour path, and a detour path search message for other nodes. A detour path search message relay means that relays a detour path search message to each section overhead, and a detour path setting message relay means that relays a detour path setting message from another node to the section overhead are provided. Configure by determining the nodes to

(Industrial Application Field) The present invention relates to a method of searching for a path that bypasses a node or link when a node or link fails in a network, and in particular, using flooding, each node autonomously searches for a path that bypasses the node or link. This invention relates to a detour path search method for searching for a path.

In a fault handling method that uses detour path formation, when a fault occurs in a node or link in a network, a path that bypasses the faulty node or link is searched for, and a cross-connect device installed in the node switches the line to resolve the fault. Create a detour path that does not pass through nodes or links.

If such a detour path search is performed using a centralized control method, the time required to search for a detour path increases as the scale of the network increases. Since there is a problem that the detour path search method using distributed control has the problem of not functioning properly, it is desirable to use a distributed control method in which each node can autonomously search for a detour path. 1. It is requested that it be able to accommodate the following.

[Conventional technology]

Conventionally, detour path search methods using centralized control methods include:
A network control center installed in the network monitors the line status, and when a node notifies that a failure has been detected, the network control center centrally performs the process of searching for a path that bypasses the failed link. It was used.

Furthermore, as a detour path search method using distributed control, a method has been used in which each node autonomously searches for a detour path by flooding.

Flanding here means that a message with only the destination specified without specifying the route is sent from the node that detected the failure to all links connected to that node.
If the node receiving this message does not correspond to its own node as the destination, the node relays the message to all links connected to that node. By repeating this procedure, the message attempts to finally reach the destination node, and is conventionally known as a routing method in packet communication, and is highly reliable. It is possible to perform routing with

Even in a detour path search method using distributed control, it is possible to search for a detour path using such flooding.

[Problem to be solved by the invention]

The detour path search method using the centralized control method has a problem in that when the scale of the network increases, the time required to search for the detour path increases. Furthermore, if the network control center itself fails, it will no longer function at all.

On the other hand, in the detour path search method using the conventional distributed control method, a detour path is searched assuming a link failure. That is, it was possible to uniquely identify the end points of the detour path as the node that detected the link failure (signal disconnection) and the node at the other end of the link. However, even in the case of a node failure, the failure is similarly detected in an adjacent node as a signal disconnection of a link connected to the failed node, so it is impossible to identify whether it is a link failure or a node failure. Therefore, the conventional detour path search method using distributed control can deal with link failures, but cannot deal with node failures.

The present invention aims to solve the problems of the prior art, and is capable of dealing with node failures in a detour path search method in which each node autonomously searches for a detour path through distributed processing using flooding. The purpose is to provide a detour path search method.

[Means to solve the problem]

As shown in FIG. 1, the basic configuration of the present invention is such that when a link or node failure occurs in a network in which multiple nodes are sequentially connected by links including multiple paths, each node autonomously uses flooding to take a detour path. In each node of the network performing the search, a path tracer generation means 1, a path tracer storage means 2, a detour path search message sending means 3, a detour path setting message return means 4, and a detour path search message relay means 5. and detour path setting message relay means 6,
The node that returned the detour path setting message is determined as the other end point of the detour path, and the node through which the detour path search message passed is determined as the node forming the detour path.

Here, the path tracer generation means 1 generates a path tracer for each path, which indicates the N nodes immediately before passing through each path, by each node writing its own node identifier in the path overhead. The path tracer storage means 2 stores the reached path tracer for each path. Further, the detour path search message sending means 3 allows the node that detected the failure to designate its own node as the end point of the detour path based on the information of the path tracer of the failure path, and select N nodes as candidates for the other end point of the detour path. The message containing the identifier is broadcast to the section overhead of all output links, and the detour path setting message return unit 4 selects the detour path when its own node corresponds to the candidate node in the broadcast detour path search message. The setup message is sent to the section overhead of the output link corresponding to the opposite route to the arrived detour path search message. Furthermore, detour path search message relay means 5
broadcasts a detour path search message of another node in the section overhead of the input link to the section overhead of all output links of its own node, and the detour path setting message relay means 6 broadcasts the detour path search message of the other node in the section overhead of the input link to the section overhead of the manual link. The detour path setting message of the other node is sent to the section overhead of the output link corresponding to the route specified by the detour path search message.

[Effect]

(+) In the detour path search method in which each node autonomously searches for a detour path using flooding, in order to respond to a node failure, it is necessary to determine which node the path affected by the failure passes through. Information regarding the path is required.

Therefore, information regarding the route of such a path (hereinafter referred to as a path tracer) is written in the overhead portion of each path and transmitted, and each node accumulates this path tracer information. However, the pass
The path information in the tracer is limited to the N nodes immediately before the node through which the path tracer passes, thereby reducing the overhead occupancy rate and the amount of information to be accumulated at each node.

(2) Furthermore, in order to search for a detour path, it is necessary to specify nodes to be switched to form a detour path. As described above, in the prior art, only a link failure was assumed, and therefore the end points of the detour path were uniquely identified as the node that detected the link failure and the node at the other end of the link. However, in the case of a node failure, the failure detection node cannot distinguish between a link failure and a node failure.

In the present invention, the node that detected the failure is set as one end point of the detour path, and the N nodes through which the path affected by the failure has passed are set as candidates for the other end point of the detour path. to search for a detour path. In other words, the node that detected the failure is one end point of the detour path, and all of the N nodes that have been affected by the failure (which can be known from the path tracer stored in the failure detection node) are included in the detour path. A detour path search message for the other end point candidate is broadcast from the failure detection node.

The node that receives this detour path search message then determines whether or not it matches the specified N node candidates, and if it does, it returns a detour path setting message.

In this case, the failed node cannot return the detour path setting message, so when the detour path setting message arrives at the failure detection node, the path between the node that sent this message and the failure detection node is changed to the desired detour path. By doing so, it means that a detour path has been searched.

(Embodiment) FIGS. 2(a), (b), and (C) show a path tracer in an embodiment of the present invention, and (a)
) describes path overhead, (b) explains reading and writing of the path tracer, and (C) explains path tracer accumulation.

The signal between nodes consists of serial information as shown in Figure 2(a), and the information in the l frame includes a section overhead for writing control information only between adjacent nodes, and control information for each path. It consists of path overhead to be written and path information bytes to write transmission data for each path.

These path tracers connect nodes AB, C, -- sequentially connected via links, as shown in FIG. 2(b).
- are respectively read/written (R/W).

The contents of the path tracer accumulated at each node are:
As shown in FIG. 2(C), it consists of an identifier (ID) indicating the upstream node through which the path has passed. However, in this embodiment, it is assumed that the number N of nodes stored in the path tracer is two.

FIG. 3 shows the configuration of a node in one embodiment of the present invention. In the figure, reference numeral 11 indicates a link, and path information bytes 12. Path overhead shown by thin solid line13. It is shown to consist of a section overhead 14 shown in dotted lines. 15 is a matrix switch, which has 12 path information bytes and 1 path overhead.
Performs cross-connection of paths consisting of 3. Reference numeral 16 denotes an alarm generating circuit (ALM), which detects a signal disconnection of the link 11 and generates a failure alarm. 17 is the section overhead interface (SECOVHINF
), which performs section overhead interface processing with the central processing unit (CPU) 21. 18 is the path overhead interface (PA
THOvHINF) with path overhead 13
and the CPU 21. 19 is the matrix switch interface (S
W INF) performs interface processing between the matrix switch 15 and the CPU 21. ALM16SECOVHI NF17. PATH0V
A path 20 connects HINF1B, SW INF19, and CPU21. CPU U21
controls all operations at the node. Also pass 2
A storage device (MEM) 22 connected to 0 stores information such as the above-mentioned path tracer and the usage status of each path.

FIG. 4 shows the configuration of a network in an embodiment of the present invention, with nodes B, C, D, X, and Y indicated by 31 to 35, and links B to 36 to 39.
C, link CD, link XC, link YC, links 40 to 45, and paths indicated by 46 to 49 (paths 1 to 4)
and detour paths (paths 1 to 4) indicated by 50 to 52.

As shown in FIG. 4, paths 1 to 4 each pass through the next node during normal operation.

Path 1: Node B - Node C - Node D Path 2: Node B - Node C - Node D Path 3: Node X - Node C -
Node D path 4: Node Y - Node C - Node D It is now assumed that a failure occurs in node C, node D detects this as a signal disconnection in link CD, and a failure alarm is generated.

In node D, the detour path search software is activated by this alarm and executes the following processing.

(1) First, a path in the link CD that passes through the node D where the alarm has occurred is searched to identify the path affected by the fault (faulty path). The failed paths in this case are paths 1 to 4.

(2) Examine the path tracers of paths 1 to 4 stored in node D, divide them into groups having the same path tracer, and calculate the number of paths belonging to each group. The groups and the number of paths belonging to each group in this case are as follows.

Group 1 (Node C - Node B) = 2 Group 2
(Node C - Node A detour path discovery message is sent to the neighboring node using the section overheads of all output links connected to node D. Each node constantly searches for the backup path and stores the information in the storage device. The following information is written in this detour path search message.

■ ID of the detour path search message source node (starting point of the detour path) ■ ID of the first node written in the path tracer
(Candidate for the end point of the detour path)■ ID of the second node written in the path tracer (Candidate for the end point of the detour path)■ Number of paths that require detour■ Requires detour IDI of the required path ID2 of the path that requires a detour For example, in the case of group 1, the information of the above-mentioned items 1 to 2 is as follows.

■ Node D ■ Node C ■ Node B ■ 2 ■ Path l ■ Path 2 (4) The node that receives the detour path search message reads the above fields ■ and ■ in the detour path search message, and determines whether its own node is detouring. Check whether it is a candidate for the end point of the path.

If the own node is not a candidate for the end point of the detour path, this detour path search message is relayed and sent to all output links that have backup paths.

If the own node is a candidate for the end point of a detour path, it sends a detour path setting message back to the source of the message via a route opposite to that of the detour path search message.

In the case of Group 1 described above, the candidates for the nodes that will become the end points of the detour path are node C and node B, but since node C is in a failure state, it does not send back the detour path setting message, and only node B uses the detour path. Since the configuration message can be sent back, node B is determined as the end point of the detour path.

As described above, according to the present invention, determining the end point of the detour path,
It is possible to simultaneously search for a detour route between the end points.

Note that although the above explanation has been made regarding the case of a failure in a node, it is clear that a failure in a link can also be dealt with in the same way.

Further, when the end points of the detour path and the detour route between the end points are determined in this way, the detour path can be set as follows.

(]) When the detour path search message sent from the failure detection node passes through each node, each node receives information indicating which node the message was sent from,
Information indicating which node the message was sent to is stored. When the detour path setting message is returned from the node that is the end point of the detour path, each node uses the information accumulated by the detour path search message to send the detour path setting message in the opposite direction to the detour path search message. At the same time, the switch of the cross-connect device of the own node is fixed to that route. By performing such a procedure at each node, a path between the start point and end point of the detour path is formed.

(2) Or, in response to the detour path search message sent from the failure detection node, a detour path setting message is returned from the node that is the end point of the detour path, and when the failure detection node is reached, the failure detection node sends the detour path search message. By sending out the formation message, the switch of the cross-connect device at each node between the start point and the end point of the detour path may be changed over to form the path.

〔Effect of the invention〕

As explained above, according to the present invention, in a detour path search method in which each node autonomously searches for a detour path through distributed processing using flooding, it becomes possible to respond to node failures, and each node The processing simultaneously executes the determination of the end point of the detour path in the event of a node failure and the search for the detour route, thereby making it possible to shorten the processing time.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the basic configuration of the present invention, Fig. 2(a),
(b) and (C) are paths in one embodiment of the present invention.
FIG. 3 is a diagram showing a tracer, FIG. 3 is a diagram showing a node configuration in an embodiment of the present invention, and FIG. 4 is a diagram showing a network configuration in an embodiment of the present invention. 1 is a path tracer generation means, 2 is a path tracer storage means, 3 is a detour path search message sending means, and 4 is a detour path setting message return means.

Claims (1)

[Claims] In each node of a network in which a plurality of nodes are sequentially connected by links including a plurality of paths, each node autonomously searches for a detour path by flooding when a link or node fails. Path tracer generation means (1) for generating a path tracer for each path indicating the N nodes immediately before passing through each path by a node writing its own node's identifier in the path overhead; a path tracer storage means (2) for storing the reached path tracer for each path; section of every output link with its identifier as a candidate for the other end of the detour path.
A detour path search message sending means (3) that broadcasts to the overhead, and corresponds to a route opposite to the detour path search message that reached the detour path setting message when the own node corresponds to the candidate node in the broadcast detour path search message. means (4) for sending a detour path setting message to the section overhead of the output link to be sent to the section overhead of the output link; and broadcasting a detour path search message of another node in the section overhead of the input link to the section overhead of all output links of the own node. A detour path search message relay means (5) transmits the detour path setting message of another node in the section overhead of the input link to the section of the output link corresponding to the route specified in the detour path search message.
a detour path setting message relay means (6) that sends out the detour path setting message to the overhead, the node that sent back the detour path setting message is set as the other end point of the detour path, and the node through which the detour path search message passes forms the detour path. A detour path search method is characterized in that a node is determined as a node.