JP2006080776A - Communication path setting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a communication path setting method capable of utilizing transmission resources in an optimized state, thereby enabling efficiently operating a network. <P>SOLUTION: In a ring network in which integer N-sets of nodes are connected into a ring, a full mesh path for coupling each of the nodes is logically formed. Next, in nodes whose node numbers are odd numbers of 1 to N/2, a path set clockwise out of paths through N/2 pieces of links is deleted. Next, in nodes whose node numbers are even numbers of 1 to N/2, a path set counterclockwise out of paths through the N/2 pieces of links is deleted. Next, in nodes in which node numbers i are N/2+1 to N and i-N/2 are odd numbers, a path set clockwise out of paths through the N/2 pieces of links is deleted. Next, in nodes in which node numbers i are N/2+1 to N and i-N/2 are even numbers, a path set counterclockwise out of paths through the N/2 pieces of links is deleted. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a communication path setting method in a network (ring network) in which a plurality of nodes are connected in a ring shape via a link.

There is a network in which a plurality of nodes are connected in a ring shape via a link. Such a topology is called a ring network and is often used for a large-scale network such as an optical submarine cable system.
In recent ring networks, an operation mode is employed in which a plurality of communication paths are multiplexed in a link and the nodes are logically fully meshed. In order to allocate transmission resources of a mesh network to a plurality of communication paths, a method for searching for an optimum route by a routing algorithm has been applied. The routing algorithm is based on the policy of optimizing the routing metric specified by, for example, bandwidth (communication processing capacity), number of node hops (distance), reliability (uptime ratio), transmission delay, etc. Search for. As this type of algorithm, a routing protocol such as OSPF (Open Shortest Path First) used for a relatively large-scale network is known.

  By the way, when a bidirectional communication path can be set in a link, there are matters to be considered according to the number of nodes. That is, in a ring network formed by an odd number of nodes, the transmission direction of the path according to the routing policy is uniquely determined. On the other hand, in a ring network formed by an even number of nodes, the routing metrics are the same in two directions, and the transmission direction to be taken may not be uniquely determined. For this reason, redundant paths are generated when the mesh topology is formed, and transmission resources are wasted, which may hinder efficient network operation.

A related technique is disclosed in Patent Document 1. This document discloses a system in which a logical mesh network is formed between nodes by setting a working path to a shorter path length in two directions of a bidirectional ring transmission path. However, this document does not consider the case where the transmission direction cannot be uniquely specified.
JP 7-66821 A

As described above, in a ring network including an even number of nodes, redundant logical paths are generated in the assumption of forming a mesh topology, which may hinder efficient network operation.
The present invention has been made in view of the above circumstances, and an object thereof is to provide a communication path setting method that enables transmission resources to be used in an optimized state, thereby enabling efficient operation of the network. It is in.

  In order to achieve the above object, according to an aspect of the present invention, at least a part of transmission resources of the link is occupied in a ring network in which an even number of nodes are connected in a ring shape via a link capable of bidirectional transmission. In the communication path setting method for setting a communication path to be set, a mesh forming step for forming a logical full mesh topology by setting a plurality of the communication paths in the ring network based on a prescribed routing protocol, Thereafter, a search step for searching for a pair of communication paths that connect the same end point nodes from opposite directions among a plurality of communication paths forming the full mesh topology, and among the pair of communication paths searched in this search step And a deletion step for deleting one of the communication paths. Set method is provided.

  By taking such measures, after the formation of the logical full mesh topology is completed, a pair of communication paths that connect the same end point nodes from opposite directions (clockwise direction and counterclockwise direction) is searched. The When this pair is found, normally, the route connecting the end point nodes should be sufficient by either the clockwise or counterclockwise communication path. That is, one of the communication path pairs is redundant, and this redundant path is deleted in the deletion step. Therefore, the usage state of the transmission resource is optimized, and the operational efficiency of the network can be improved.

  According to the present invention, it becomes possible to use a transmission resource in an optimized state, thereby providing a communication path setting method capable of operating a network efficiently.

  FIG. 1 is a system diagram showing an embodiment of a digital signal transmission system according to the present invention. Hereinafter, the system in FIG. 1 will be described as conforming to SDH, but the same applies to a system conforming to SONET. In FIG. 1, n nodes N1 to Nn are connected in a ring shape via an optical fiber OF. The optical fiber OF has a service line SL and a protection line PL as its backup system, and each of the lines SL and PL includes a clockwise (CW: Clockwise) line and a counterclockwise (CCW: Counter Clockwise) line. The optical fiber OF transmits an optical signal generated by electrical / optical conversion of a high-speed multiplexed signal such as an STM-64 (Synchronous Transfer Module-Level 64) signal.

  The nodes N1 to Nn drop a predetermined slot from the time slot that is time-division multiplexed on the STM-64 signal frame transmitted through the optical fiber OF, and then transfer this slot to the low-order group side switch or the like on the low-speed line SC. To send out. The nodes N1 to Nn add low-order group signals such as STM-1, STM-4, and STM-16 sent from the exchange or the like via the low-speed line SC to predetermined slots of the STM-64 frame, Send to node. In this way, a path having a predetermined transmission capacity is set between the nodes N1 to Nn. Transmission resources in this system are time slots that are time-division multiplexed on SDH frames. In an all-optical network, each optical wavelength multiplexed on a link is a transmission resource.

  Each of the nodes N1 to Nn is connected to monitoring control devices M1 to Mn via, for example, a LAN (Local Area Network). Each of the monitoring control devices M1 to Mn is realized, for example, by installing dedicated application software on a general-purpose workstation, and various types such as path setting and alarm monitoring in the network based on notification information respectively notified from the nodes N1 to Nn. Execute control.

FIG. 2 is a schematic diagram illustrating a process of forming a logical full mesh path in a unidirectional ring network. Note that the number of nodes is N. In FIG. 2, each node establishes a path from its own node to a destination node via N-1 links, that is, a path to all other nodes on the network. Can be formed. The number of resource usage in this case is expressed by the following equation (1). 2 to 4, the CW link indicates a clockwise link, and the CCW link indicates a counter clockwise link.

FIG. 3 is a schematic diagram illustrating a process of forming a logical full mesh path in a bidirectional ring network having an odd number of nodes. That is, the number of nodes N is an odd number. In FIG. 3, each node can logically form a full mesh topology with a plurality of paths by setting a path from its own node to a destination node via (N-1) / 2 links. it can. The number of resource usage in this case is expressed by the following equation (2).

FIG. 4 is a schematic diagram illustrating a process of forming a logical full mesh path in a bidirectional ring network having an even number of nodes. That is, the number N of nodes is an even number. In FIG. 4, each node sets a path from its own node to a destination node via N / 2 links, whereby a full mesh topology with a plurality of paths can be logically formed. The number of resource usage in this case is expressed by the following equation (3).

  By the way, in a ring network having an even number of nodes as shown in FIG. 4, the length of a route passing through N / 2 links is maximum. According to existing routing protocols, the cost of this route is estimated to be the highest. However, there are two routes having the maximum cost, the clockwise direction and the counterclockwise direction. If this route is left as it is, a redundant path is generated and the operation efficiency of the network is lowered. This is a particular situation in a ring network having an even number of nodes.

  FIG. 5 is a diagram illustrating an example of a redundant path in the ring network illustrated in FIG. In FIG. 5, N = 6. As shown by the dotted line in FIG. 5, there is a CW link path connecting, for example, the node 1 and the node (N / 2 + 1). Also in the CCW link, there is a path connecting the node 1 and the node (N / 2 + 1) from the opposite direction. One of these pairs of paths is redundant. The same thing occurs with resources indicated by two-dot chain lines in the figure. If such a redundant path occurs, the utilization efficiency of transmission resources cannot be optimized.

[First Embodiment]
FIG. 6 is a diagram illustrating a state in which redundant paths are deleted from the state of FIG. In this embodiment, the redundant path is deleted from the net by the following procedure.
(Procedure 1-1) First, all the paths from each node to one to N / 2 links are set in the ring network. That is, a path that passes through only one link, a path that passes through two links, and a path that passes through three links are set from each node.
(Procedure 1-2) Next, node number 1 is assigned to any one node on the network.
(Procedure 1-3) From node No. 1 to other nodes, numbers from 2, 3,..., N (6) are assigned clockwise.
(Procedure 1-4) N / 2 (that is, three) links that are set clockwise and counterclockwise in an odd-numbered node having a node number of 1 to N / 2 (that is, 1 to 3). Delete the paths that are set clockwise from the paths that pass through.
(Procedure 1-5) In even-numbered nodes with node numbers 1 to N / 2, set in a counterclockwise direction among paths passing through N / 2 links set in a clockwise direction and a counterclockwise direction Delete the specified path.
(Procedure 1-6) In a node where the node number i is from N / 2 + 1 to N and i-N / 2 is an odd number, via N / 2 links set clockwise and counterclockwise Among the paths to be deleted, the path set in the clockwise direction is deleted.
(Procedure 1-7) In a node where the node number i is N / 2 + 1 to N and i−N / 2 is an even number, via N / 2 links set clockwise and counterclockwise Delete the path set counterclockwise among the paths to be performed.

  With the above procedure, the path is deleted from the resources indicated by the dotted line and the two-dot chain line in the CW direction as shown in FIG. In the CCW direction, the path is deleted from the resource indicated by the alternate long and short dash line.

  As described above, in this embodiment, in a ring network in which an even number of N nodes are connected in a ring shape via a link capable of bidirectional transmission, first, a full mesh path that connects the nodes is logically formed. From this state, the paths set in the clockwise direction are deleted from among the paths passing through N / 2 links in the odd numbered nodes having node numbers 1 to N / 2. Next, among the paths that pass through N / 2 links in even-numbered nodes with node numbers 1 to N / 2, the paths that are set counterclockwise are deleted. Next, a path set in the clockwise direction is deleted from the paths passing through N / 2 links in the nodes having node numbers i of N / 2 + 1 to N and i-N / 2 being an odd number. . Next, the path set in the counterclockwise direction is deleted from the paths passing through N / 2 links in the nodes where the node number i is N / 2 + 1 to N and i−N / 2 is an even number. Like to do.

  Since it did in this way, it becomes possible to search and eliminate an upper communication path, and a full mesh topology can be formed using a minimum necessary communication path. Therefore, the transmission resource can be used in an optimized state, thereby enabling efficient operation of the network.

[Second Embodiment]
FIG. 7 is a schematic diagram showing a process in the middle of forming a full mesh path in the ring network shown in FIG. In the first embodiment, a full mesh path is once formed, and then a redundant path is deleted. In the second embodiment, a procedure for deleting a redundant path in parallel with setting a communication path and finally forming a full mesh topology will be described. In the following description, the number of nodes N = 6.

(Procedure 2-1) First, all the paths from each node to 1 to (N / 2-1) links are set in the ring network. That is, all the paths that pass through only one link and the paths that pass through two links are set from each node. This state corresponds to FIG.
(Procedure 2-2) Next, node number 1 is assigned to any one node on the network.
(Procedure 2-3) Numbers 2, 3,..., N (6) are assigned clockwise from the node of node number 1 to other nodes.
(Procedure 2-4) In odd nodes with node numbers 1 to N / 2, a path passing through N / 2 links is set counterclockwise.

  (Procedure 2-5) In an even-numbered node having node numbers 1 to N / 2, a path passing through N / 2 links is set clockwise.

  (Procedure 2-6) In the node where the node number i is N / 2 + 1 to N and i-N / 2 is an odd number, a path passing through N / 2 links is set counterclockwise.

  (Procedure 2-7) In a node where the node number i is N / 2 + 1 to N and i-N / 2 is an even number, a path passing through N / 2 links is set clockwise.

  By such a procedure, a full mesh topology is finally formed through the state shown in FIG. As described above, in this embodiment, after setting all the paths that pass through 1 to N / 2-1 links, only the paths that do not become redundant among the paths that pass through N / 2 links are set. . In this way, transmission resources can be used in an optimized state, and the network can be operated efficiently.

  In addition, this invention is not limited to the said embodiment, In the implementation stage, it can embody by modifying a component in the range which does not deviate from the summary. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

1 is a system diagram showing an embodiment of a digital signal transmission system according to the present invention. The schematic diagram which shows the process in which a logical full mesh path is formed in a unidirectional ring network. The schematic diagram which shows the process in which a logical full mesh path is formed in a bidirectional | two-way ring network provided with an odd number of nodes. The schematic diagram which shows the process in which a logical full mesh path is formed in a bidirectional | two-way ring network provided with an even number of nodes. The figure which shows an example of the redundant path in the ring network shown in FIG. The figure which shows the state which deleted the redundant path from the state of FIG. The schematic diagram which shows the process in the middle of forming a full mesh path in the ring network shown in FIG. FIG. 8 is a schematic diagram illustrating a state from the state illustrated in FIG. 7 to a full mesh topology.

Explanation of symbols

  N1 to Nn: Node, OF: Optical fiber, SL: Service line, PL: Protection line, SC: Low speed line, M1 to Mn: Monitoring and control device

Claims (4)

In a communication path setting method for setting a communication path that occupies at least a part of transmission resources of the link in a ring network in which an even number of nodes are connected in a ring shape via a link capable of bidirectional transmission,
A mesh forming step of forming a logical full mesh topology by setting a plurality of the communication paths in the ring network based on a prescribed routing protocol;
After this mesh formation step, a search step for searching for a pair of communication paths that connect the same end node from opposite directions among a plurality of communication paths forming the full mesh topology;
A communication path setting method comprising: a deletion step of deleting one of the communication path pairs searched in the search step. In a communication path setting method for setting a communication path that occupies at least a part of transmission resources of the link in a ring network in which an even number of nodes are connected in a ring shape via a link capable of bidirectional transmission,
A path setting step for sequentially setting a plurality of communication paths in the ring network based on a prescribed routing protocol;
A search step of searching for a pair of communication paths that connect the same end point nodes from opposite directions among the plurality of communication paths formed in the path setting step;
A deletion step of deleting one of the communication path pairs searched in the search step;
A communication path setting method comprising: a mesh formation step of forming a logical full mesh topology in the ring network by sequentially repeating the path setting step, the search step, and the deletion step. When multiple pairs of communication paths are searched in the search step,
3. The communication path setting method according to claim 1, wherein the deleting step deletes a clockwise communication path from each of the plurality of communication path pairs. When multiple pairs of communication paths are searched in the search step,
3. The communication path setting method according to claim 1, wherein the deleting step deletes a communication path in a counterclockwise direction from each of the plurality of communication path pairs.

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