Node apparatus, ring network, and protection path bandwidth control method

This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2009-17032, filed on Jan. 28, 2009, the entire contents of which are incorporated herein by reference.

The embodiment(s) discussed herein is(are) related to a method for controlling a protection path to be used for wrapping control in a ring network in which a plurality of node apparatuses are connected in a ring configuration.

FIG. 1A is an explanatory diagram illustrating one example of a prior art protection path setup method used in a ring network constructed by connecting a plurality of node apparatuses in a ring configuration. The ring network NT includes the plurality of node apparatuses N 1 to N 6 , and links L 1 to L 6 connecting between the adjacent node apparatuses N 1 and N 2 , N 2 and N 3 , N 3 and N 4 , N 4 and N 5 , N 5 and N 6 , and N 6 and N 1 , respectively. The node apparatuses N 1 to N 6 are connected in a ring configuration by the links L 1 to L 6 .

To provide protection by wrapping control for a working path A passing through the ring network NT, the ring network NT provides a protection path A′ that has the same bandwidth as the working path A and that cycles around the ring network NT in a direction opposite to the signal transporting direction of the working path A. In the event of a failure of the working path A, one of the node apparatuses adjacent to the failure wraps the signal flowing on the working path back onto the protection path, that is, the signal is looped back. Then, the signal is transported up to the other node apparatus adjacent to the failure by using the protection path A′ that transports the signal in the direction opposite to the working path A, thereby making it possible to circumvent the failure. The other node apparatus adjacent to the failure loops back the signal flowing on the protection path onto the working path, and the signal is thus transported over the working path to the designated endpoint node.

FIG. 1B is an explanatory diagram illustrating how wrapping control is performed in the event of a failure. It is assumed here that a failure has occurred on the link L 6 through which the working path A passes. One node apparatus N 6 adjacent to the failure loops back the signal flowing on the working path A onto the protection path A′. The protection path A′ transports the signal via the node apparatuses N 6 , N 5 , N 4 , N 3 , N 2 , and N 1 in this order in the direction opposite to the signal transporting direction of the working path A. The other node apparatus N 1 adjacent to the failure loops back the signal flowing on the protection path A′ onto the working path A. Then, the working path A transports the signal up to the endpoint node N 4 via the node apparatuses N 1 , N 2 , N 3 , and N 4 in this order.

In the prior art wrapping control, the ring network provides a dedicated protection path for each working path. FIG. 2 is an explanatory diagram illustrating one example of the prior art protection path setup method when there are a plurality of working paths. In the illustrated ring network NT, the working paths A, B, and C having bandwidths of 50 Mbps, 70 Mbps, and 100 Mbps, respectively, are set up. The working path A is set up from the startpoint node apparatus N 6 to the endpoint node N 4 by passing through the node apparatuses N 6 , N 1 , N 2 , N 3 , and N 4 in this order. The working path B is set up from the startpoint node apparatus N 3 to the endpoint node N 5 by passing through the node apparatuses N 3 , N 4 , and N 5 in this order. The working path C is set up from the startpoint node apparatus N 6 to the endpoint node N 2 by passing through the node apparatuses N 6 , N 1 , and N 2 in this order. In the ring network NT, protection paths A′, B′, and C′ are provided in a one-to-one corresponding relationship to the working paths A, B, and C.

A communication network has been proposed that performs failure recovery in the following manner in a first communication in which a signal is inserted at the i-th communication node of a plurality of communication nodes and terminated at the j-th communication node around a first ring. When a failure of the first communication is detected, the j-th communication node sends a request message to the i-th communication node to reroute the first communication along a second ring. Upon receiving the request message, the i-th communication node switches the communication path of the first communication from the first ring to the second ring, thereby accomplishing failure recovery of the first communication. Further, the communication network performs failure recovery in the following manner in a second communication in which a signal is inserted at the m-th communication node of the plurality of communication nodes and terminated at the n-th communication node around a third ring. When a failure of the second communication is detected, the n-th communication node sends a request message to the m-th communication node to reroute the second communication along a fourth ring. Upon receiving the request message, the m-th communication node switches the communication path of the second communication from the third ring to the fourth ring, thereby accomplishing failure recovery of the second communication.

On the other hand, in a network system in which data is transferred over a path predefined between nodes, there is proposed a connection-type network node, such as described below, that can be a startpoint node of a protection path that provides a bypass route for a protection section contained in the working path. This connection-type network node includes a bandwidth usage amount determining unit and a generating unit. When setting up a protection path, the bandwidth usage amount determining unit determines the amount of bandwidth usage of the protection path to be set up, based on the working path that contains the protection section to be protected by that protection path. When the sum of the thus determined bandwidth usage and the current protection path bandwidth usage of an interface that transmits the data out onto that protection path does not exceed the usable amount of protection path bandwidth predetermined for that interface, the generating unit generates a signaling message for setting up the protection path.

There is also a redundancy protection mechanism and automatic protection switching (APS) that has been proposed in which a shared protection ring is applied to a T-MPLS (Transport MPLS) layer network defined in ITU-T Recommendations G.8110.

[Patent document 1] Japanese Unexamined Patent Publication No. H11-163911 [Patent document 2] Japanese Unexamined Patent Publication No. 2007-49573 [Non-patent document 1] “Draft ITU-T Rec. G8132/Y.1382 (T-MPLS shared protection ring),” February 2008, International Telecommunication Union—Telecommunication Standardization Sector

The protection path setup method described with reference to FIG. 2 has been inefficient in the utilization of network bandwidth resources because a larger bandwidth than would normally be necessary has been reserved for the protection paths. That is, the total bandwidth that would normally be necessary in order to reserve the same bandwidth resources for the protection paths as for the working paths would be given by the largest value among the per-link total values of the bandwidths that the working paths use on the respective links, but in the above protection path setup method, a larger bandwidth than this largest value has been provided for the protection paths.

For example, in the example of FIG. 2 , when the working paths A to C are set up in the ring network NT, the largest value among the total values of the bandwidths used by the working paths A to C is 150 Mbps which is used on the links L 1 and L 6 . However, in the ring network NT, bandwidth resources amounting to 220 Mbps in total are reserved for the protection paths A′ to C′.

According to an embodiment, a protection path setup method is provided for a ring network in which a plurality of node apparatuses are connected in a ring configuration, and in which, to provide protection for a working path passing through the ring network, a protection path is provided that cycles around the ring network and that transports a signal in a direction opposite to the signal transporting direction of the working path and, in the event of a failure of the working path, a node apparatus adjacent to the failure loops back the signal flowing on the working path onto the protection path.

In this method, at each of the node apparatuses, a maximum total bandwidth value, which represents the largest value among the per-link total values of the bandwidths that a plurality of working paths use on respective links connecting between the respective node apparatuses, is stored in a prescribed storing unit as an allowable bandwidth for a shared path provided to be shared as a protection path among the plurality of working paths, and at each of the node apparatuses, the bandwidth of traffic flowing on the protection path is controlled in accordance with the allowable bandwidth.

The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed.

FIG. 1A is an explanatory diagram (part 1 ) illustrating one example of a prior art protection path setup method;

FIG. 1B is an explanatory diagram illustrating how wrapping control is performed in the event of a failure;

FIG. 2 is an explanatory diagram (part 2 ) illustrating one example of the prior art protection path setup method;

FIG. 3 is a diagram illustrating one configuration example of a ring network discussed herein;

FIG. 4 is an explanatory diagram of a shared path;

FIG. 5 is a diagram illustrating one configuration example of a node apparatus depicted in FIG. 3 ;

FIG. 6 is a diagram illustrating one example of the data structure of a transfer table depicted in FIG. 5 ;

FIG. 7 is a diagram illustrating one example of the data structure of a queue table depicted in FIG. 5 ;

FIG. 8 is a diagram illustrating one example of the data structure of a path table depicted in FIG. 5 ;

FIG. 9 is a diagram illustrating one configuration example of a bandwidth control unit depicted in FIG. 5 ;

FIG. 10 is a diagram illustrating one example of the data structure of a shared path table depicted in FIG. 5 ;

FIG. 11 is a flowchart (part 1 ) illustrating one example of the processing performed when a control command is received from an NMS;

FIG. 12 is a flowchart (part 2 ) illustrating one example of the processing performed when a control command is received from the NMS;

FIG. 13 is a diagram illustrating one example of the data structure of instruction information contained in a working path setup command;

FIG. 14 is a diagram illustrating one example of the data structure of instruction information contained in a working path change command;

FIG. 15 is a diagram illustrating one example of the data structure of instruction information contained in a protection path setup command;

FIG. 16 is a diagram illustrating one example of the data structure of instruction information contained in a protection path change command;

FIG. 17 is a flowchart (part 1 ) illustrating one example of the processing performed when a control message is received;

FIG. 18 is a flowchart (part 2 ) illustrating one example of the processing performed when a control message is received;

FIG. 19 is a diagram illustrating a first example of the data structure of instruction information contained in a working path setup message;

FIG. 20 is a diagram illustrating one example of the data structure of instruction information contained in a working path change message;

FIG. 21 is a diagram illustrating one example of the data structure of instruction information contained in a protection path setup message;

FIG. 22 is a diagram illustrating one example of the data structure of instruction information contained in a protection path change message;

FIG. 23 is a flowchart illustrating an example of a bandwidth control method for protection path traffic;

FIG. 24 is an explanatory diagram illustrating an example of a method for changing the allowable bandwidth of the shared path in response to the setup of a new working path;

FIG. 25 is a diagram illustrating a second example of the data structure of the instruction information contained in the working path setup message; and

FIG. 26 is a flowchart illustrating one example of the processing performed in response to the reception of the working path setup message.

Embodiments will be described below with reference to the accompanying drawings. FIG. 3 is a diagram illustrating one configuration example of a ring network discussed herein. The ring network NT includes a plurality of node apparatuses N 1 to N 6 , links L 1 to L 6 connecting between the respective adjacent node apparatuses, and a network management system (NMS) 10 which sets up paths passing through the ring network NT. The links L 1 to L 6 form the ring network NT by connecting between the adjacent node apparatuses N 1 and N 2 , N 2 and N 3 , N 3 and N 4 , N 4 and N 5 , N 5 and N 6 , and N 6 and N 1 , respectively, thereby connecting the node apparatuses N 1 to N 6 in a ring configuration.

To provide protection by wrapping control for a working path passing through the ring network NT, the ring network NT provides a protection path that has the same bandwidth as the working path and that cycles around the ring network NT in a direction opposite to the signal transporting direction of the working path. The ring network NT according to the present embodiment reserves bandwidth resources for a shared path to be shared as a protection path among a plurality of working paths, rather than reserving protection path bandwidth resources independently for each working path.

FIG. 4 is an explanatory diagram of the shared path. In the illustrated ring network NT, working paths A and B having bandwidths of 50 Mbps and 70 Mbps, respectively, are set up. The working path A is set up from the startpoint node apparatus N 6 to the endpoint node N 4 by passing through the node apparatuses N 6 , N 1 , N 2 , N 3 , and N 4 in this order. The working path B is set up from the startpoint node apparatus N 5 to the endpoint node N 2 by passing through the node apparatuses N 5 , N 6 , N 1 , and N 2 in this order. The ring network NT reserves bandwidth resources for the shares path P as the bandwidth resources to be shared by the protection paths A′ and B′ having bandwidths of 50 Mbps and 70 Mbps in corresponding relationship to the respective working paths A and B.

The bandwidth resources reserved for the shared path P are given as the largest value among the per-link total values of the bandwidths that the working paths A and B use on the respective links L 1 to L 6 connecting between the respective node apparatuses N 1 to N 6 . In the following description, the largest value among the per-link total values may sometimes be called the “maximum total bandwidth value.” In the case of the working paths A and B illustrated in FIG. 4 , the maximum total bandwidth value is 120 Mbps which is used on the links L 6 and L 1 where the working paths A and B overlap. Therefore, bandwidth resources equivalent to 120 Mbps are reserved for the shared path P. This maximum total bandwidth value represents the minimum necessary bandwidth to achieve a protection path having the same bandwidth as the working paths A and B.

FIG. 5 is a diagram illustrating one configuration example of the node apparatus N 1 depicted in FIG. 3 . The configuration is the same for the other node apparatuses N 2 to N 6 . Reference character 11 indicates a switch unit, reference character 12 indicates a storage unit, reference characters 13 and 14 indicate bandwidth control units, and reference characters 15 and 16 indicate failure detection units.

Reference character 21 indicates a control message receiving unit, reference character 22 indicates a control message transmitting unit, reference character 23 indicates a command processing unit, and reference character 24 indicates a control message processing unit. Reference character 40 indicates a shared path message processing unit, reference character 41 indicates a working path message processing unit, and reference character 42 indicates a protection path message processing unit.

Reference character T 1 indicates a transfer table, reference character T 2 indicates a queue table, reference character T 3 indicates a path table, and reference character T 4 indicates a shared path table.

The node apparatus N 1 includes the switch unit 11 , storage unit 12 , bandwidth control units 13 and 14 , failure detection units 15 and 16 , control message receiving unit 21 , control message transmitting unit 22 , command processing unit 23 , and control message processing unit 24 .

The switch unit 11 performs processing to transfer a traffic signal, received at one of a plurality of ports connected to the links to the adjacent node apparatuses, to a designated one of the other ports. Of the plurality of ports, only the port 1 connected to the adjacent node apparatus N 6 and the port 2 connected to the adjacent node apparatus N 2 are depicted in FIG. 5 , but the node apparatus N 1 may further include other ports.

Based on the contents of the transfer table T 1 stored in the storage unit 12 , the switch unit 11 determines to which port the received traffic signal is to be transferred. FIG. 6 is a diagram illustrating one example of the data structure of the transfer table T 1 depicted in FIG. 5 . The transfer table T 1 has a path ID field, an input port field, an output port field, an alternate port field, and a corresponding path ID field, and a record containing these fields is stored for each path passing through the node apparatus 1 .

The path ID field carries the identifier of each designated path, and the input port field carries the identifier of the port at which the traffic signal on the designated path is input. The output port field carries the identifier of the port at which the traffic signal on the designated path is to be output.

The alternate port field carries the output port to which the traffic signal on the designated path is to be looped back for output when a failure is detected on the output side of the traffic signal. When the designated path is a working path, the corresponding path ID field carries the identifier of the protection path provided to back up that working path. When the designated path is a protection path, the corresponding path ID field carries the identifier of the working path backed up by that protection path.

The data contents of the transfer table T 1 depicted in FIG. 6 correspond to the data contents for the case where the working paths A and B, the protection paths A′ and B′, and the shared path P have been set up as described with reference to FIG. 4 . For the working path A, the port 1 connected to the adjacent node apparatus N 6 is designated as the input port, and the port 2 connected to the adjacent node apparatus N 2 is designated as the output port. When a failure is detected on the downstream side of the output port 2 , the node apparatus N 1 recovers from this failure through wrapping control by looping the traffic signal on the working path A back to the port 1 . For this reason, the alternate port field carries the identifier of the port 1 . The corresponding path ID field carries the identifier of the protection path A′.

Likewise, for the protection path A′, the port 2 is designated as the input port, and the port 1 as the output port. When a failure is detected on the downstream side of the output port 1 , the node apparatus N 1 loops the traffic signal on the protection path A′ back to the port 2 ; accordingly, the alternate port field carries the identifier of the port 2 . The corresponding path ID field carries the identifier of the working path A.

For the working path B, the port 1 is designated as the input port, and the port 2 as the output port. When a failure is detected on the downstream side of the output port 2 , the node apparatus N 1 loops the traffic signal on the working path B back to the port 1 ; accordingly, the alternate port field carries the identifier of the port 1 . The corresponding path ID field carries the identifier of the protection path B′. For the protection path B′, the port 2 is designated as the input port, and the port 1 as the output port. When a failure is detected on the downstream side of the output port 1 , the node apparatus N 1 loops the traffic signal on the protection path B′ back to the port 2 ; accordingly, the alternate port field carries the identifier of the port 2 . The corresponding path ID field carries the identifier of the working path B.

For the shared path P, which is a path used as the bandwidth resources for the protection paths A′ and B′, the port 2 is designated as the input port, and the port 1 as the output port. For the shared path P, data entries to the alternate port field and the corresponding path ID field may be omitted.

The switch unit 11 in FIG. 5 refers to the path identifier contained in the header information of the received traffic signal. The switch unit 11 identifies the output port specified in the transfer table T 1 for that path identifier. If no failure is detected at the identified output port by the failure detection unit 15 or 16 to be described later, the switch unit 11 transfers the traffic signal to that identified output port. If a failure is detected at the identified output port, the switch unit 11 transfers the traffic signal to the alternate port specified in the transfer table T 1 .

The bandwidth control units 13 and 14 in FIG. 5 control the bandwidth of the traffic signal on each path in accordance with the contents of the queue table T 2 and path table T 3 stored in the storage unit 12 . FIG. 7 is a diagram illustrating one example of the data structure of the queue table T 2 depicted in FIG. 5 . The queue table T 2 has a queue field and an allowable bandwidth field, and a record containing these fields is stored for each queue used for bandwidth control by the bandwidth control units 13 and 14 . The queue field carries the identifier of each designated queue. The allowable bandwidth field carries the bandwidth allowable for the traffic that is output from each designated queue.

The data contents of the queue table T 2 depicted in FIG. 7 correspond to the case where the paths have been set up as described with reference to FIG. 4 . Queue 1 is used for the bandwidth control of the traffic on the protection paths that use the bandwidth resources of the shared path P, and 120 Mbps is reserved as the allowable bandwidth. Queue 2 is used for the bandwidth control of the traffic on the working path A, and 50 Mbps is reserved as the allowable bandwidth. Queue 3 is used for the bandwidth control of the traffic on the working path B, and 70 Mbps is reserved as the allowable bandwidth.

FIG. 8 is a diagram illustrating one example of the data structure of the path table T 3 depicted in FIG. 5 . The path table T 3 has a path ID field and an associated queue field, and a record containing these fields is stored for each of the currently set working paths and protection paths. The path ID field carries the identifier of each designated path. The associated queue field carries the identifier of the queue to be used by the bandwidth control units 13 and 14 for the bandwidth control of the designated queue.

The data contents of the path table T 3 depicted in FIG. 8 correspond to the case where the paths have been set up as described with reference to FIG. 4 . The queues to be used for the bandwidth control of the working paths A and B are the queues 2 and 3 , respectively. The queue to be used for the bandwidth control of the protection paths A′ and B′ that use the bandwidth resources of the same shared path P is the queue 1 .

FIG. 9 is a diagram illustrating one configuration example of the bandwidth control unit 14 depicted in FIG. 5 . The configuration is the same for the bandwidth control unit 13 . Reference character 60 indicates a distributor, reference character 61 indicates a plurality of queues, and reference character 62 indicates a scheduler. The bandwidth control unit 14 includes the distributor 60 , the plurality of queues 61 , and the scheduler 62 .

The distributor 60 refers to the path identifier contained in the header information of the traffic signal received from the switch unit 11 , and distributes the traffic signal to the queue specified for that path identifier in the path table T 3 from among the plurality of queues 61 . The scheduler 62 controls the amount of traffic to be output from each queue in accordance with the allowable bandwidth specified for a corresponding one of the plurality of queues 61 in the queue table T 2 .

The failure detection units 15 and 16 detect a failure occurring on the links connected to the respective ports 1 and 2 , and notify the switch unit 11 . For example, when the signal arriving via the port 1 or 2 has ceased for a predefined period of time, the failure detection unit 15 or 16 determines that a failure has occurred on the link connected to that port.

The control message receiving unit 21 performs processing to receive a prescribed control message from a node apparatus adjacent to the node apparatus N 1 . The kinds of the control message include working path setup message, working path change message, and working path delete message which respectively request the setup, changing, and deletion of a working path from a certain node apparatus to another node apparatus.

The kinds of the control message also include shared path setup message, shared path change message, and shared path delete message which respectively request the setup, changing, and deletion of a shared path from a certain node apparatus to another node apparatus. The kinds of the control message further include protection path setup message, protection path change message, and protection path delete message which respectively request the setup, changing, and deletion of a protection path from a certain node apparatus to another node apparatus. The control message transmitting unit 22 performs processing to transmit the control message to the adjacent node apparatus.

When the control message receiving unit 21 receives the control message of any one of the above enumerated kinds, the control message processing unit 24 changes the setting for the node apparatus N 1 by updating the contents of a corresponding one or ones of the tables T 1 to T 4 in the storage unit 12 in accordance with the received control message. The kind of the control message is not limited to any one of the above enumerated kinds, and a control message of a kind other than the above enumerated kinds may be received; in that case also, the control message processing unit 24 changes the setting for the node apparatus N 1 in accordance with the contents of the received message. The control message processing unit 24 includes the shared path message processing unit 40 , working path message processing unit 41 , and protection path message processing unit 42 .

When the received control message is a shared path setup message, the shared path message processing unit 40 creates, in the shared path table T 4 stored in the storage unit 12 , an entry for the identifier of the new shared path specified in the shared path setup message. FIG. 10 is a diagram illustrating one example of the data structure of the shared path table T 4 depicted in FIG. 5 . The shared path table T 4 has a path ID field and an associated queue field, and a record containing these fields is stored for each shared path provided in the node apparatus N 1 .

The path ID field carries the identifier of each designated shared path. The associated queue field carries the identifier of the queue that is used, from among the plurality of queues 61 in the bandwidth control unit 13 or 14 , to control the traffic on the protection path that uses the bandwidth resources of the designated shared path. The data contents of the shared path table T 4 depicted in FIG. 10 correspond to the case where the paths have been set up as described with reference to FIG. 4 . In the example illustrated in FIG. 4 , the shared path P is set up, and the queue 1 is the queue used to control the traffic on the protection path that uses the bandwidth resources of the shared path P.

In response to the reception of the shared path setup message, the shared path message processing unit 40 generates a queue to be used for the new shared path, and creates an entry for this queue in the queue table T 2 . The value of bandwidth information specified in the shared path setup command is stored in the allowable bandwidth field of the thus created entry. Further, the shared path message processing unit 40 creates an entry for the new shared path in the shared path table T 4 , and stores in the associated queue field the identifier of the queue for which the entry has been created in the queue table T 2 .

Based on the routing information contained in the shared path setup message, the shared path message processing unit 40 determines the input port and output port via which the traffic on the protection path that uses the bandwidth resources of the new shared path is input and output. The shared path message processing unit 40 creates an entry for the new shared path in the transfer table T 1 , and stores the identifiers of the thus determined input port and output port in its input port field and output port field, respectively.

When the received control message is a shared path change message, the shared path message processing unit 40 refers to the identifier of the shared path specified in the shared path change message, and identifies the queue specified in the shared path table T 4 for that shared path. The shared path message processing unit 40 changes the value of the allowable bandwidth, specified in the queue table T 2 for that queue, to the value specified in the shared path change message.

When the received control message is a shared path delete message, the shared path message processing unit 40 refers to the identifier of the shared path specified in the shared path delete message, and deletes the entries for that shared path from the shared path table T 4 and transfer table T 1 . It also deletes from the queue table T 2 the entry for the queue specified in the shared path table T 4 for that shared path.

The control message includes routing information which specifies the node apparatuses located along the transmission path of the message and the ports for receiving and transmitting the message at each node apparatus. When the node apparatus that received the shared path setup message, shared path change message, or shared path delete message is not the endpoint of that message, the shared path message processing unit 40 instructs the control message transmitting unit 22 to transfer the message to the next node apparatus.

When the received control message is a working path setup message, the working path message processing unit 41 generates a queue to be used for the new working path, and creates an entry for this queue in the queue table T 2 . The value of bandwidth information specified in the working path setup command is stored in the allowable bandwidth field of the thus created entry.

Further, the working path message processing unit 41 creates in the path table T 3 an entry for the identifier of the new working path specified in the working path setup message, and stores in the associated queue field the identifier of the queue for which the new entry has been created in the queue table T 2 . Based on the routing information contained in the working path setup message, the working path message processing unit 41 determines the input port and output port via which the traffic on the new working path is input and output. The working path message processing unit 41 creates an entry for the new working path in the transfer table T 1 , and stores the identifiers of the thus determined input port and output port in its input port field and output port field, respectively.

When the received control message is a working path change message, the working path message processing unit 41 refers to the identifier of the working path specified in the working path change message, and identifies the queue specified in the path table T 3 for that working path. The working path message processing unit 41 changes the value of the allowable bandwidth, specified in the queue table T 2 for that queue, to the value specified in the working path change message.

When the received control message is a working path delete message, the working path message processing unit 41 refers to the identifier of the working path specified in the working path delete message, and deletes the entries for that working path from the path table T 3 and transfer table T 1 . It also deletes from the queue table T 2 the entry for the queue specified in the path table T 3 for that working path.

When the node apparatus that received the working path setup message, working path change message, or working path delete message is not the endpoint of that message, the working path message processing unit 41 instructs the control message transmitting unit 22 to transfer the message to the next node apparatus.

When the received control message is a protection path setup message, the protection path message processing unit 42 creates in the path table T 3 an entry for the identifier of the new protection path specified in the protection path setup message. The protection path message processing unit 42 refers to the identifier of the shared path specified in the protection path setup message as being the path whose bandwidth resources are to be used by the new protection path, and identifies the queue specified in the shared path table T 4 for that shared path. The protection path message processing unit 42 stores the identifier of the thus identified queue in the associated queue field of the entry newly created in the path table T 3 .

Based on the routing information contained in the protection path setup message, the protection path message processing unit 42 determines the input port and output port via which the traffic on the new protection path is input and output. The protection path message processing unit 42 creates an entry for the new protection path in the transfer table T 1 , and stores the identifiers of the thus determined input port and output port in its input port field and output port field, respectively.

The protection path message processing unit 42 stores, in the corresponding path ID field of the entry created in the transfer table T 1 for the new protection path, the identifier of the working path specified in the protection path setup message as being the path to be backed up by that new protection path. Further, the protection path message processing unit 42 identifies the output port specified in the transfer table T 1 for the above working path specified in the protection path setup message, and stores it in the alternate port field of the entry created for the new protection path.

Further, the protection path message processing unit 42 stores the output port of the new protection path and the identifier of the new protection path, respectively, in the alternate port field and corresponding ID field of the entry provided in the transfer table T 1 for the above working path specified in the protection path setup message.

When the received control message is a protection path change message, the protection path message processing unit 42 identifies the queue specified in the shared path table T 4 for the shared path specified in the protection path change message. The protection path message processing unit 42 enters the identifier of the thus identified queue to update the value stored in the associated queue field of the entry provided in the path table T 3 for the protection path specified in the protection path change message.

When the received control message is a protection path delete message, the protection path message processing unit 42 refers to the identifier of the protection path specified in the protection path delete message, and deletes the entries for that protection path from the path table T 3 and transfer table T 1 .

When the node apparatus that received the protection path setup message, protection path change message, or protection path delete message is not the endpoint of that message, the protection path message processing unit 42 instructs the control message transmitting unit 22 to transfer the message to the next node apparatus.

The command processing unit 23 in FIG. 5 receives a prescribed control command from the NMS 10 , and passes the received command to the shared path message processing unit 40 , the working path message processing unit 41 , or the protection path message processing unit 42 , whichever is appropriate, according to the kind of the command. The kinds of the control command include working path setup command, working path change command, and working path delete command which respectively request the setup, changing, and deletion of a working path.

The kinds of the control command also include shared path setup command, shared path change command, and shared path delete command which respectively request the setup, changing, and deletion of a shared path. The kinds of the control command further include protection path setup command, protection path change command, and protection path delete command which respectively request the setup, changing, and deletion of a protection path. The kind of the control command is not limited to any one of the above enumerated kinds, and a control command of a kind other than the above enumerated kinds may be received; in that case also, the command processing unit 23 changes the setting for the node apparatus N 1 in accordance with the contents of the received command.

When any one of the shared path setup command, shared path change command, and shared path delete command is received, the command processing unit 23 passes the command to the shared path message processing unit 40 . When any one of the shared path setup command, shared path change command, and shared path delete command is received, the shared path message processing unit 40 performs the same processing as when the shared path setup message, shared path change message, or shared path delete message, respectively, is received.

For the control command to be transmitted to all the nodes related to the path to be set up, changed, or deleted, the control command includes routing information which specifies the node apparatuses located along the transmission path of the command and the ports for receiving and transmitting the message at each node apparatus. The shared path message processing unit 40 creates the shared path setup message, shared path change message, or shared path delete message for requesting the same control operation as that specified by the shared path setup command, shared path change command, or shared path delete command, respectively. Here, the shared path message processing unit 40 creates the shared path setup message, shared path change message, or shared path delete message by also including routing information for the path that passes through the route specified by the routing information contained in the corresponding control command. The shared path message processing unit 40 instructs the control message transmitting unit 22 to transfer the control message to the node apparatus specified as the next node by the routing information.

When any one of the working path setup command, working path change command, and working path delete command is received, the command processing unit 23 passes the command to the working path message processing unit 41 . When any one of the working path setup command, working path change command, and working path delete command is received, the working path message processing unit 41 performs the same processing as when the working path setup message, working path change message, or working path delete message, respectively, is received.

The working path message processing unit 41 creates the working path setup message, working path change message, or working path delete message for requesting the same control operation as that specified by the working path setup command, working path change command, or working path delete command, respectively. Here, the working path message processing unit 41 creates the working path setup message, working path change message, or working path delete message by also including routing information for the path that passes through the route specified by the routing information contained in the corresponding control command. The working path message processing unit 41 instructs the control message transmitting unit 22 to transfer the control message to the node apparatus specified as the next node by the routing information.

When any one of the protection path setup command, protection path change command, and protection path delete command is received, the command processing unit 23 passes the command to the protection path message processing unit 42 . When any one of the protection path setup command, protection path change command, the protection path delete command is received, the protection path message processing unit 42 performs the same processing as when the protection path setup message, protection path change message, or protection path delete message, respectively, is received.

The protection path message processing unit 42 creates the protection path setup message, protection path change message, or protection path delete message for requesting the same control operation as that specified by the protection path setup command, protection path change command, or protection path delete command, respectively. The protection path message processing unit 42 creates the protection path setup message, protection path change message, or protection path delete message by also including routing information for the path that passes through the route specified by the routing information contained in the corresponding control command. The protection path message processing unit 42 instructs the control message transmitting unit 22 to transfer the control message to the node apparatus specified as the next node by the routing information.

The operation of the node apparatus N 1 will be described below. FIGS. 11 and 12 are flowcharts illustrating one example of the processing that the node apparatus N 1 performs in response to the reception of a control command from the NMS 10 . In step S 1 , the command processing unit 23 receives the control command from the NMS 10 . In step S 2 , the command processing unit 23 determines whether the received command is a working path setup command or not. If the received command is not a working path setup command (N in step S 2 ), the command processing unit 23 proceeds to step S 4 .

If the received command is a working path setup command (Y in step S 2 ), the command processing unit 23 passes the working path setup command to the working path message processing unit 41 , and the process proceeds to step S 3 . FIG. 13 is a diagram illustrating one example of the data structure of the instruction information contained in the working path setup command. The data structure of the instruction information contained in the working path setup command includes fields for storing “kind code,” “path ID,” “routing information,” “bandwidth information,” and “protection path ID.”

The kind code is a code that indicates to which of a plurality of kinds, including the earlier enumerated kinds, the control command belongs. The path ID indicates the identifier of the new working path to be set up. The routing information specifies the route through which the new working path passes. For example, the routing information may be information that specifies a set of identifiers identifying the node apparatuses located along the route of the designated path, the identifiers being arranged in the order in which the path passes through the respective nodes, and the ports that are used at each node apparatus to receive and transmit out the traffic signal flowing on the path. The bandwidth information specifies the allowable bandwidth requested of the new working path. The protection path ID indicates the identifier of the protection path used to back up the new working path.

In step S 3 , the working path message processing unit 41 generates a queue to be used for the new working path, and creates an entry for this queue in the queue table T 2 . The value of bandwidth information specified in the working path setup command is stored in the allowable bandwidth field of the thus created entry. The working path message processing unit 41 creates in the path table T 3 an entry for the identifier of the working path specified by the working path setup command, and stores in the associated queue field the identifier of the queue for which the new entry has been created in the queue table T 2 .

Based on the routing information contained in the working path setup command, the working path message processing unit 41 determines the input port and output port via which the traffic on the new working path is input to and output from the node apparatus N 1 . The working path message processing unit 41 creates an entry for the new working path in the transfer table T 1 , and stores the identifiers of the thus determined input port and output port in its input port field and output port field, respectively. After that, the working path message processing unit 41 proceeds to step S 21 .

In step S 21 , the working path message processing unit 41 creates a working path setup message by including therein the path ID, bandwidth information, and protection path ID contained in the working path setup command. The working path message processing unit 41 creates the working path setup message by also including routing information for the new working path based on the routing information contained in the working path setup command. The working path message processing unit 41 instructs the control message transmitting unit 22 to transfer the working path setup message to the adjacent node apparatus specified as the next node, i.e., the downstream node by the routing information, and thereafter causes the process to terminate.

In step S 4 , the command processing unit 23 determines whether the received command is a working path change command or not. If the received command is not a working path change command (N in step S 4 ), the command processing unit 23 proceeds to step S 6 .

If the received command is a working path change command (Y in step S 4 ), the command processing unit 23 passes the working path change command to the working path message processing unit 41 , and the process proceeds to step S 5 . FIG. 14 is a diagram illustrating one example of the data structure of the instruction information contained in the working path change command. The data structure of the instruction information contained in the working path change command includes fields for storing “kind code,” “path ID,” “routing information,” and “bandwidth information.”

The path ID indicates the identifier of the working path to be changed. The routing information specifies the route through which the working path to be changed passes. The bandwidth information specifies the allowable bandwidth requested of the working path to be changed.

In step S 5 , the working path message processing unit 41 refers to the identifier of the working path specified by the working path change command, and identifies the queue specified in the path table T 3 for that working path. The working path message processing unit 41 changes the value of the allowable bandwidth, specified in the queue table T 2 for that queue, to the value specified by the bandwidth information contained in the working path change command. After that, the working path message processing unit 41 proceeds to step S 21 .

In step S 21 , the working path message processing unit 41 creates a working path change message by including therein the path ID and bandwidth information contained in the working path change command. The working path message processing unit 41 creates the working path change message by also including routing information for the working path to be changed, based on the routing information contained in the working path change command. The working path message processing unit 41 instructs the control message transmitting unit 22 to transfer the working path change message to the adjacent node apparatus specified as the downstream node by the routing information, and thereafter causes the process to terminate.

In step S 6 , the command processing unit 23 determines whether the received command is a working path delete command or not. If the received command is not a working path delete command (N in step S 6 ), the command processing unit 23 proceeds to step S 8 .

If the received command is a working path delete command (Y in step S 6 ), the command processing unit 23 passes the working path delete command to the working path message processing unit 41 , and the process proceeds to step S 7 . The data structure of the instruction information contained in the working path delete command may be the same as that depicted in FIG. 14 . The path ID indicates the identifier of the working path to be deleted. The routing information specifies the route through which the working path to be deleted passes.

In step S 7 , the working path message processing unit 41 refers to the identifier of the working path specified by the working path delete command, and deletes the entries for that working path from the path table T 3 and transfer table T 1 . It also deletes from the queue table T 2 the entry for the queue specified in the path table T 3 for that working path. After that, the working path message processing unit 41 proceeds to step S 21 .

In step S 21 , the working path message processing unit 41 creates a working path delete message by including therein the path ID contained in the working path delete command. The working path message processing unit 41 creates the working path delete message by also including routing information for the working path to be deleted, based on the routing information contained in the working path delete command. The working path message processing unit 41 instructs the control message transmitting unit 22 to transfer the working path delete message to the adjacent node apparatus specified as the downstream node by the routing information, and thereafter causes the process to terminate.

In step S 8 , the command processing unit 23 determines whether the received command is a shared path setup command or not. If the received command is not a shared path setup command (N in step S 8 ), the command processing unit 23 proceeds to step S 10 .

If the received command is a shared path setup command (Y in step S 8 ), the command processing unit 23 passes the shared path setup command to the shared path message processing unit 40 , and the process proceeds to step S 9 . The data structure of the instruction information contained in the shared path setup command may be the same as that depicted in FIG. 14 . The path ID indicates the identifier of the new shared path to be set up. The routing information specifies the route through which the new shared path passes. The bandwidth information specifies the allowable bandwidth requested of the new shared path.

When creating the shared path setup command to be transmitted to the node apparatus N 1 , the NMS 10 specifies the largest value among the per-link total values of the bandwidths that the existing working paths use on the respective links L 1 to L 6 , that is, the maximum total bandwidth value, as the bandwidth information.

In step S 9 , the shared path message processing unit 40 generates a queue to be used for the bandwidth control of the protection path that uses the bandwidth resources of the new shared path, and creates an entry for this queue in the queue table T 2 . The value of bandwidth information specified in the shared path setup command is stored in the allowable bandwidth field of the thus created entry. The shared path message processing unit 40 creates an entry for the new shared path in the shared path table T 4 , and stores in the associated queue field the identifier of the queue for which the new entry has been created in the queue table T 2 .

Based on the routing information contained in the shared path setup command, the shared path message processing unit 40 determines the input port and output port via which the traffic on the protection path that uses the bandwidth resources of the new shared path is input to and output from the node apparatus N 1 . The shared path message processing unit 40 creates an entry for the new shared path in the transfer table T 1 , and stores the identifiers of the thus determined input port and output port in its input port field and output port field, respectively. After that, the shared path message processing unit 40 proceeds to step S 21 .

In step S 21 , the shared path message processing unit 40 creates a shared path setup message by including therein the path ID and bandwidth information contained in the shared path setup command. The shared path message processing unit 40 creates the shared path setup message by also including routing information for the new shared path based on the routing information contained in the shared path setup command. The shared path message processing unit 40 instructs the control message transmitting unit 22 to transfer the shared path setup message to the adjacent node apparatus specified as the downstream node by the routing information, and thereafter causes the process to terminate.

In step S 10 , the command processing unit 23 determines whether the received command is a shared path change command or not. If the received command is not a shared path change command (N in step S 10 ), the command processing unit 23 proceeds to step S 12 .

If the received command is a shared path change command (Y in step S 10 ), the command processing unit 23 passes the shared path change command to the shared path message processing unit 40 , and the process proceeds to step S 11 . The data structure of the instruction information contained in the shared path change command may be the same as that depicted in FIG. 14 . The path ID indicates the identifier of the shared path to be changed. The routing information specifies the route through which the shared path to be changed passes. The bandwidth information specifies the new allowable bandwidth requested of the shared path to be changed.

When creating the shared path change command to be transmitted to the node apparatus N 1 , the NMS 10 specifies the largest value among the per-link total values of the bandwidths that the existing working paths use on the respective links L 1 to L 6 , i.e., the maximum total bandwidth value, as the bandwidth information.

In step S 11 , the shared path message processing unit 40 refers to the identifier of the shared path specified by the shared path change command as being the path to be changed, and identifies the queue specified in the shared path table T 4 for that shared path. The shared path message processing unit 40 changes the value of the allowable bandwidth, specified in the queue table T 2 for that queue, to the value specified as the bandwidth information by the shared path change command. After that, the shared path message processing unit 40 proceeds to step S 21 .

In step S 21 , the shared path message processing unit 40 creates a shared path change message by including therein the path ID and bandwidth information contained in the shared path change command. The shared path message processing unit 40 creates the shared path change message by also including routing information for the shared path to be changed, based on the routing information contained in the shared path change command. The shared path message processing unit 40 instructs the control message transmitting unit 22 to transfer the shared path change message to the adjacent node apparatus specified as the downstream node by the routing information, and thereafter causes the process to terminate.

In step S 12 , the command processing unit 23 determines whether the received command is a shared path delete command or not. If the received command is not a shared path delete command (N in step S 12 ), the command processing unit 23 proceeds to step S 14 .

If the received command is a shared path delete command (Y in step S 12 ), the command processing unit 23 passes the shared path delete command to the shared path message processing unit 40 , and the process proceeds to step S 13 . The data structure of the instruction information contained in the shared path delete command may be the same as that depicted in FIG. 14 . The path ID indicates the identifier of the shared path to be deleted. The routing information specifies the route through which the shared path to be deleted passes.

In step S 13 , the shared path message processing unit 40 refers to the identifier of the shared path specified by the shared path delete command, and deletes the entries for that shared path from the shared path table T 4 and transfer table T 1 . It also deletes from the queue table T 2 the entry for the queue specified in the shared path table T 4 for that shared path. After that, the shared path message processing unit 40 proceeds to step S 21 .

In step S 21 , the shared path message processing unit 40 creates a shared path delete message by including therein the path ID contained in the shared path delete command. The shared path message processing unit 40 creates the shared path delete message by also including routing information for the shared path to be deleted, based on the routing information contained in the shared path delete command. The shared path message processing unit 40 instructs the control message transmitting unit 22 to transfer the shared path delete message to the adjacent node apparatus specified as the downstream node by the routing information, and thereafter causes the process to terminate.

In step S 14 , the command processing unit 23 determines whether the received command is a protection path setup command or not. If the received command is not a protection path setup command (N in step S 14 ), the command processing unit 23 proceeds to step S 16 .

If the received command is a protection path setup command (Y in step S 14 ), the command processing unit 23 passes the protection path setup command to the protection path message processing unit 42 , and the process proceeds to step S 15 . FIG. 15 is a diagram illustrating one example of the data structure of the instruction information contained in the protection path setup command. The data structure of the instruction information contained in the protection path setup command includes fields for storing “kind code,” “path ID,” “routing information,” “bandwidth information,” “working path ID,” and “shared path ID.”

The path ID indicates the identifier of the new protection path to be set up. The routing information specifies the route through which the new protection path passes. The working path ID indicates the identifier of the working path to be backed up by the new protection path. The shared path ID indicates the identifier of the shared path whose bandwidth resources are to be used by the new protection path.

When creating protection path setup commands respectively to set up a plurality of protection paths that use the same bandwidth resources, the NMS 10 specifies the identifier of the same shared path as the shared path ID in the protection path setup commands.

In step S 15 , the protection path message processing unit 42 creates in the path table T 3 an entry for the identifier of the new protection path specified by the protection path setup command. The protection path message processing unit 42 refers to the identifier of the shared path specified in the protection path setup command as being the path whose bandwidth resources are to be used by the new protection path, and identifies the queue specified in the shared path table T 4 for that shared path. The protection path message processing unit 42 stores the identifier of the thus identified queue in the associated queue field of the entry newly created in the path table T 3 .

Based on the routing information contained in the protection path setup command, the protection path message processing unit 42 determines the input port and output port via which the traffic on the new protection path is input and output. The protection path message processing unit 42 creates an entry for the new protection path in the transfer table T 1 , and stores the identifiers of the thus determined input port and output port in its input port field and output port field, respectively.

The protection path message processing unit 42 stores, in the corresponding path ID field of the entry created in the transfer table T 1 for the new protection path, the identifier of the working path specified in the protection path setup command as being the path to be backed up by that new protection path. Further, the protection path message processing unit 42 identifies the output port specified in the transfer table T 1 for the above working path specified in the protection path setup command, and stores it in the alternate port field of the entry created for the new protection path.

Further, the protection path message processing unit 42 stores the output port of the new protection path and the identifier of the new protection path, respectively, in the alternate port field and corresponding ID field of the entry provided in the transfer table T 1 for the above working path specified in the protection path setup command. After that, the protection path message processing unit 42 proceeds to step S 21 .

In step S 21 , the protection path message processing unit 42 creates a protection path setup message by including therein the path ID, working path ID, and shared path ID contained in the protection path setup command. The protection path message processing unit 42 creates the protection path setup message by also including routing information for the new protection path based on the routing information contained in the protection path setup command. The protection path message processing unit 42 instructs the control message transmitting unit 22 to transfer the protection path setup message to the adjacent node apparatus specified as the downstream node by the routing information, and thereafter causes the process to terminate.

In step S 16 , the command processing unit 23 determines whether the received command is a protection path change command or not. If the received command is not a protection path change command (N in step S 16 ), the command processing unit 23 proceeds to step S 18 .

If the received command is a protection path change command (Y in step S 16 ), the command processing unit 23 passes the protection path change command to the protection path message processing unit 42 , and the process proceeds to step S 17 . FIG. 16 is a diagram illustrating one example of the data structure of the instruction information contained in the protection path change command. The data structure of the instruction information contained in the protection path change command includes fields for storing “kind code,” “path ID,” “routing information,” “bandwidth information,” and “shared path ID.”

The path ID indicates the identifier of the protection path to be changed. The routing information specifies the route through which the protection path to be changed passes. The shared path ID indicates the identifier of the shared path whose bandwidth resources are used by the protection path to be changed. When creating a protection path change command for causing a certain protection path to use the same bandwidth resources as those used by some other protection path, the NMS 10 specifies as the shared path ID in the protection path change command the identifier of the shared path whose bandwidth resources are used by that other protection path.

In step S 17 , the protection path message processing unit 42 identifies the queue specified in the shared path table T 4 for the shared path specified in the protection path change command. The protection path message processing unit 42 enters the identifier of the thus identified queue to update the value stored in the associated queue field of the entry provided in the path table T 3 for the protection path specified by the protection path change command. After that, the protection path message processing unit 42 proceeds to step S 21 .

In step S 21 , the protection path message processing unit 42 creates a protection path change message by including therein the path ID and shared path ID contained in the protection path change command. The protection path message processing unit 42 creates the protection path change message by also including routing information for the protection path to be changed, based on the routing information contained in the protection path change command. The protection path message processing unit 42 instructs the control message transmitting unit 22 to transfer the protection path change message to the adjacent node apparatus specified as the downstream node by the routing information, and thereafter causes the process to terminate.

In step S 18 , the command processing unit 23 determines whether the received command is a protection path delete command or not. If the received command is not a protection path delete command (N in step S 18 ), the command processing unit 23 proceeds to step S 20 .

If the received command is a protection path delete command (Y in step S 18 ), the command processing unit 23 passes the protection path delete command to the protection path message processing unit 42 , and the process proceeds to step S 19 . The data structure of the instruction information contained in the protection path delete command may be the same as that depicted in FIG. 14 . The path ID indicates the identifier of the protection path to be deleted. The routing information specifies the route through which the protection path to be deleted passes.

In step S 17 , the protection path message processing unit 42 refers to the identifier of the protection path specified by the protection path delete command, and deletes the entries for that protection path from the path table T 3 and transfer table T 1 . After that, the protection path message processing unit 42 proceeds to step S 21 .

In step S 21 , the protection path message processing unit 42 creates a protection path delete message by including therein the path ID contained in the protection path delete command. The protection path message processing unit 42 creates the protection path delete message by also including routing information for the protection path to be deleted, based on the routing information contained in the protection path delete command. The protection path message processing unit 42 instructs the control message transmitting unit 22 to transfer the protection path delete message to the adjacent node apparatus specified as the downstream node by the routing information, and thereafter causes the process to terminate.

If the control command received in step S 1 is a command that specifies a control operation other than the setup, changing, or deletion of a working, shared, or protection path, the process proceeds to S 20 . The command processing unit 23 processes the command accordingly, and thereafter causes the process to terminate.

FIGS. 17 and 18 are flowcharts illustrating one example of the processing that the node apparatus N 1 performs in response to the reception of a control message from a node apparatus adjacent to it. In step S 30 , the control message receiving unit 21 receives the control message from the adjacent node apparatus. In step S 31 , the control message receiving unit 21 determines whether the received control message is a working path setup message or not. If the received control message is not a working path setup message (N in step S 31 ), the control message receiving unit 21 proceeds to step S 33 .

If the received message is a working path setup message (Y in step S 31 ), the control message receiving unit 21 passes the working path setup message to the working path message processing unit 41 , and proceeds to step S 32 . FIG. 19 is a diagram illustrating a first example of the data structure of the instruction information contained in the working path setup message. The data structure of the instruction information contained in the working path setup message includes fields for storing “kind code,” “path ID,” “routing information,” “bandwidth information,” and “protection path ID.”

The kind code is a code that indicates to which of a plurality of kinds, including the earlier enumerated kinds, the control message belongs. The path ID indicates the identifier of the new working path to be set up. The routing information specifies the route along which the new working path is to be set up, i.e., the route along which the working path setup message is to be transmitted. The data structure of the routing information may be the same as that of the routing information contained in the control command transmitted from the NMS 10 . The bandwidth information specifies the allowable bandwidth requested of the new working path. The protection path ID indicates the identifier of the protection path used to back up the new working path.

In step S 32 , the working path message processing unit 41 performs processing to set up the new working path in a manner similar to that described in connection with step S 3 in FIG. 11 . After that, the working path message processing unit 41 proceeds to step S 50 .

In step S 50 , the working path message processing unit 41 determines whether the node apparatus N 1 is the endpoint of the route specified by the routing information carried in the working path setup message. If the node apparatus N 1 is the endpoint (Y in step S 50 ), the working path message processing unit 41 causes the process to terminate. If the node apparatus N 1 is not the endpoint (N in step S 50 ), then in step S 51 the working path message processing unit 41 instructs the control message transmitting unit 22 to transfer the working path setup message to the adjacent node apparatus specified as the downstream node by the routing information, and thereafter causes the process to terminate.

In step S 33 , the control message receiving unit 21 determines whether the received control message is a working path change message or not. If the received control message is not a working path change message (N in step S 33 ), the control message receiving unit 21 proceeds to step S 35 .

If the received message is a working path change message (Y in step S 33 ), the control message receiving unit 21 passes the working path change message to the working path message processing unit 41 , and the process proceeds to step S 34 . FIG. 20 is a diagram illustrating one example of the data structure of the instruction information contained in the working path change message. The data structure of the instruction information contained in the working path change message includes fields for storing “kind code,” “path ID,” “routing information,” and “bandwidth information.”

The path ID indicates the identifier of the working path to be changed. The routing information specifies the route through which the working path to be changed passes, that is, the route along which the working path change message is to be transmitted. The bandwidth information specifies the allowable bandwidth requested of the working path to be changed.

In step S 34 , the working path message processing unit 41 performs processing to change the working path in a manner similar to that described in connection with step S 5 in FIG. 11 . After that, the working path message processing unit 41 proceeds to step S 50 .

In step S 50 , the working path message processing unit 41 determines whether the node apparatus N 1 is the endpoint of the route specified by the routing information carried in the working path change message. If the node apparatus N 1 is the endpoint (Y in step S 50 ), the working path message processing unit 41 causes the process to terminate. If the node apparatus N 1 is not the endpoint (N in step S 50 ), then in step S 51 the working path message processing unit 41 instructs the control message transmitting unit 22 to transfer the working path change message to the adjacent node apparatus specified as the downstream node by the routing information, and thereafter causes the process to terminate.

In step S 35 , the control message receiving unit 21 determines whether the received control message is a working path delete message or not. If the received control message is not a working path delete message (N in step S 35 ), the control message receiving unit 21 proceeds to step S 37 .

If the received message is a working path delete message (Y in step S 35 ), the control message receiving unit 21 passes the working path delete message to the working path message processing unit 41 , and the process proceeds to step S 36 . The data structure of the instruction information contained in the working path delete message may be the same as that depicted in FIG. 20 . The path ID indicates the identifier of the working path to be deleted. The routing information specifies the route through which the working path to be deleted passes, i.e., the route along which the working path delete message is to be transmitted.

In step S 36 , the working path message processing unit 41 performs processing to delete the working path in a manner similar to that described in connection with step S 7 in FIG. 11 . After that, the working path message processing unit 41 proceeds to step S 50 .

In step S 50 , the working path message processing unit 41 determines whether the node apparatus N 1 is the endpoint of the route specified by the routing information carried in the working path delete message. If the node apparatus N 1 is the endpoint (Y in step S 50 ), the working path message processing unit 41 causes the process to terminate. If the node apparatus N 1 is not the endpoint (N in step S 50 ), then in step S 51 the working path message processing unit 41 instructs the control message transmitting unit 22 to transfer the working path delete message to the adjacent node apparatus specified as the downstream node by the routing information, and thereafter causes the process to terminate.

In step S 37 , the control message receiving unit 21 determines whether the received control message is a shared path setup message or not. If the received control message is not a shared path setup message (N in step S 37 ), the control message receiving unit 21 proceeds to step S 39 .

If the received message is a shared path setup message (Y in step S 37 ), the control message receiving unit 21 passes the shared path setup message to the shared path message processing unit 40 , and the process proceeds to step S 38 . The data structure of the instruction information contained in the shared path setup message may be the same as that depicted in FIG. 20 . The path ID indicates the identifier of the new shared path to be set up. The routing information specifies the route through which the new shared path passes, that is, the route along which the shared path setup message is to be transmitted. The bandwidth information specifies the allowable bandwidth requested of the new shared path.

In step S 38 , the shared path message processing unit 40 performs processing to set up the new shared path in a manner similar to that described in connection with step S 9 in FIG. 11 . After that, the shared path message processing unit 40 proceeds to step S 50 .

In step S 50 , the shared path message processing unit 40 determines whether the node apparatus N 1 is the endpoint of the route specified by the routing information carried in the shared path setup message. If the node apparatus N 1 is the endpoint (Y in step S 50 ), the shared path message processing unit 40 causes the process to terminate. If the node apparatus N 1 is not the endpoint (N in step S 50 ), then in step S 51 the shared path message processing unit 40 instructs the control message transmitting unit 22 to transfer the shared path setup message to the adjacent node apparatus specified as the downstream node by the routing information, and thereafter causes the process to terminate.

In step S 39 , the control message receiving unit 21 determines whether the received control message is a shared path change message or not. If the received control message is not a shared path change message (N in step S 39 ), the control message receiving unit 21 proceeds to step S 41 .

If the received message is a shared path change message (Y in step S 39 ), the control message receiving unit 21 passes the shared path change message to the shared path message processing unit 40 , and the process proceeds to step S 40 . The data structure of the instruction information contained in the shared path change message may be the same as that depicted in FIG. 20 . The path ID indicates the identifier of the shared path to be changed. The routing information specifies the route through which the shared path to be changed passes, i.e., the route along which the shared path change message is to be transmitted. The bandwidth information specifies the new allowable bandwidth requested of the shared path to be changed.

In step S 40 , the shared path message processing unit 40 performs processing to change the shared path in a manner similar to that described in connection with step S 11 in FIG. 11 . After that, the shared path message processing unit 40 proceeds to step S 50 .

In step S 50 , the shared path message processing unit 40 determines whether the node apparatus N 1 is the endpoint of the route specified by the routing information carried in the shared path change message. If the node apparatus N 1 is the endpoint (Y in step S 50 ), the shared path message processing unit 40 causes the process to terminate. If the node apparatus N 1 is not the endpoint (N in step S 50 ), then in step S 51 the shared path message processing unit 40 instructs the control message transmitting unit 22 to transfer the shared path change message to the adjacent node apparatus specified as the downstream node by the routing information, and thereafter causes the process to terminate.

In step S 41 , the control message receiving unit 21 determines whether the received control message is a shared path delete message or not. If the received control message is not a shared path delete message (N in step S 41 ), the control message receiving unit 21 proceeds to step S 43 .

If the received message is a shared path delete message (Y in step S 41 ), the control message receiving unit 21 passes the shared path delete message to the shared path message processing unit 40 , and the process proceeds to step S 42 . The data structure of the instruction information contained in the shared path delete message may be the same as that depicted in FIG. 20 . The path ID indicates the identifier of the shared path to be deleted. The routing information specifies the route through which the shared path to be deleted passes, i.e., the route along which the shared path delete message is to be transmitted.

In step S 42 , the shared path message processing unit 40 performs processing to delete the shared path in a manner similar to that described in connection with step S 13 in FIG. 11 . After that, the shared path message processing unit 40 proceeds to step S 50 .

In step S 50 , the shared path message processing unit 40 determines whether the node apparatus N 1 is the endpoint of the route specified by the routing information carried in the shared path delete message. If the node apparatus N 1 is the endpoint (Y in step S 50 ), the shared path message processing unit 40 causes the process to terminate. If the node apparatus N 1 is not the endpoint (N in step S 50 ), then in step S 51 the shared path message processing unit 40 instructs the control message transmitting unit 22 to transfer the shared path delete message to the adjacent node apparatus specified as the downstream node by the routing information, and thereafter causes the process to terminate.

In step S 43 , the control message receiving unit 21 determines whether the received control message is a protection path setup message or not. If the received control message is not a protection path setup message (N in step S 43 ), the control message receiving unit 21 proceeds to step S 45 .

If the received message is a protection path setup message (Y in step S 43 ), the control message receiving unit 21 passes the protection path setup message to the protection path message processing unit 42 , and the process proceeds to step S 44 . FIG. 21 is a diagram illustrating one example of the data structure of the instruction information contained in the protection path setup message. The data structure of the instruction information contained in the protection path setup message includes fields for storing “kind code,” “path ID,” “routing information,” “bandwidth information,” “working path ID,” and “shared path ID.”

The path ID indicates the identifier of the new protection path to be set up. The routing information specifies the route along which the new protection path is to be set up, i.e., the route along which the protection path setup message is to be transmitted. The working path ID indicates the identifier of the working path to be backed up by the new protection path. The shared path ID indicates the identifier of the shared path whose bandwidth resources are to be used by the new protection path.

In step S 44 , the protection path message processing unit 42 performs processing to set up the new protection path in a manner similar to that described in connection with step S 15 in FIG. 12 . After that, the protection path message processing unit 42 proceeds to step S 50 .

In step S 50 , the protection path message processing unit 42 determines whether the node apparatus N 1 is the endpoint of the route specified by the routing information carried in the protection path setup message. If the node apparatus N 1 is the endpoint (Y in step S 50 ), the protection path message processing unit 42 causes the process to terminate. If the node apparatus N 1 is not the endpoint (N in step S 50 ), then in step S 51 the protection path message processing unit 42 instructs the control message transmitting unit 22 to transfer the protection path setup message to the adjacent node apparatus specified as the downstream node by the routing information, and thereafter causes the process to terminate.

In step S 45 , the control message receiving unit 21 determines whether the received control message is a protection path change message or not. If the received control message is not a protection path change message (N in step S 45 ), the control message receiving unit 21 proceeds to step S 47 .

If the received message is a protection path change message (Y in step S 45 ), the control message receiving unit 21 passes the protection path change message to the protection path message processing unit 42 , and the process proceeds to step S 46 . FIG. 22 is a diagram illustrating one example of the data structure of the instruction information contained in the protection path change message. The data structure of the instruction information contained in the protection path change message includes fields for storing “kind code,” “path ID,” “routing information,” “bandwidth information,” and “shared path ID.”

The path ID indicates the identifier of the protection path to be changed. The routing information specifies the route through which the protection path to be changed passes, that is, the route along which the protection path change message is to be transmitted. The shared path ID indicates the identifier of the shared path whose bandwidth resources are used by the protection path to be changed.

In step S 46 , the protection path message processing unit 42 performs processing to change the protection path in a manner similar to that described in connection with step S 17 in FIG. 12 . After that, the protection path message processing unit 42 proceeds to step S 50 .

In step S 50 , the protection path message processing unit 42 determines whether the node apparatus N 1 is the endpoint of the route specified by the routing information carried in the protection path change message. If the node apparatus N 1 is the endpoint (Y in step S 50 ), the protection path message processing unit 42 causes the process to terminate. If the node apparatus N 1 is not the endpoint (N in step S 50 ), then in step S 51 the protection path message processing unit 42 instructs the control message transmitting unit 22 to transfer the protection path change message to the adjacent node apparatus specified as the downstream node by the routing information, and thereafter causes the process to terminate.

In step S 47 , the control message receiving unit 21 determines whether the received control message is a protection path delete message or not. If the received control message is not a protection path delete message (N in step S 47 ), the control message receiving unit 21 proceeds to step S 49 .

If the received message is a protection path delete message (Y in step S 47 ), the control message receiving unit 21 passes the protection path delete message to the protection path message processing unit 42 , and the process proceeds to step S 48 . The data structure of the instruction information contained in the protection path delete message may be the same as that depicted in FIG. 20 .

The path ID indicates the identifier of the protection path to be deleted. The routing information specifies the route through which the protection path to be deleted passes, i.e., the route along which the protection path delete message is to be transmitted.

In step S 46 , the protection path message processing unit 42 performs processing to delete the protection path in a manner similar to that described in connection with step S 19 in FIG. 12 . After that, the protection path message processing unit 42 proceeds to step S 50 .

In step S 50 , the protection path message processing unit 42 determines whether the node apparatus N 1 is the endpoint of the route specified by the routing information carried in the protection path delete message. If the node apparatus N 1 is the endpoint (Y in step S 50 ), the protection path message processing unit 42 causes the process to terminate. If the node apparatus N 1 is not the endpoint (N in step S 50 ), then in step S 51 the protection path message processing unit 42 instructs the control message transmitting unit 22 to transfer the protection path delete message to the adjacent node apparatus specified as the downstream node by the routing information, and thereafter causes the process to terminate.

FIG. 23 is a flowchart illustrating an example of a bandwidth control method for protection path traffic. In step S 60 , the node apparatus N 1 receives the traffic signal. In step S 61 , the switch unit 11 refers to the path identifier contained in the header information of the received traffic signal. The switch unit 11 identifies the output port to which the received traffic signal is to be directed, based on the contents of the output port field of the entry stored in the transfer table T 1 for that path identifier.

The switch unit 11 determines whether or not the failure detection unit 15 or 16 has detected any failure at the identified output port. If no failure is detected (N in step S 61 ), the switch unit 11 proceeds to step S 62 . If any failure has been detected (Y in step S 61 ), the switch unit 11 proceeds to step S 63 .

In step S 62 , the switch unit 11 directs the traffic signal to the output port identified in step S 61 . On the other hand, in step S 63 , the switch unit 11 directs the traffic signal to the port specified in the alternate port field of the entry stored in the transfer table T 1 for the path identifier contained in the header information of the traffic signal. With the above steps S 61 to S 63 , the switch unit 11 performs failure recovery by wrapping control when a failure has occurred at the output port.

In step S 64 , the distributor 60 in the bandwidth control unit 13 or 14 that received the traffic signal from the switch unit 11 refers to the path identifier contained in the header information of the traffic signal received from the switch unit 11 , and distributes the traffic signal to the queue specified for that path identifier in the path table T 3 from among the plurality of queues 61 .

The queue specified for any given protection path in the path table T 3 is the queue specified in the shared path table T 4 for the shared path whose bandwidth resources are used by that protection path. Accordingly, the traffic signal arriving from the protection path is distributed to the queue specified in the shared path table T 4 for the shared path whose bandwidth resources are used by that protection path.

When a plurality of protection paths are specified by the protection path setup or protection path change command or the protection path setup or protection path change message so that the plurality of protection paths use the bandwidth resources of the same shared path, the traffic signal arriving from any of these protection paths is distributed to the same queue. For example, in the example of the path table T 3 depicted in FIG. 8 , the traffic signals arriving from the protection paths A′ and B′ are both distributed to the queue 1 specified for the shaped path P.

In step S 65 , the scheduler 62 controls the amount of traffic to be output from the queue in accordance with the allowable bandwidth specified for a corresponding one of the plurality of queues 61 in the queue table T 2 .

The allowable bandwidth specified in the queue table T 2 for the queue to which the protection path is allocated is given by the maximum total bandwidth value specified in the shared path setup or shared path change command or the shared path setup or shared path change message for the shared path whose bandwidth resources are used by that protection path. More specifically, when creating the shared path setup command to be transmitted to the node apparatus N 1 , the largest value among the per-link total values of the bandwidths that the existing working paths use on the respective links L 1 to L 6 , i.e., the maximum total bandwidth value, is specified as the allowable bandwidth.

With the above steps S 64 and S 65 , the traffic on the protection path is controlled so that the traffic on the shared path does not exceed the maximum total bandwidth value specified for the shared path whose bandwidth resources are used by that protection path. When a plurality of protection paths are specified so as to share the bandwidth resources of the same shared path, control is performed so that the total amount of traffic on these protection paths does not exceed the maximum total bandwidth value. In step S 66 , the bandwidth control unit 13 or 14 delivers the traffic controlled by the scheduler 62 to the designated output port for output.

According to the present embodiment, bandwidth resources for a plurality of protection paths are reserved as the bandwidth resources of the shared path to be shared by the plurality of protection paths. The maximum total bandwidth value, i.e., the largest value among the per-link total values of the bandwidths that the working paths use on the respective links L 1 to L 6 , is used as the allowable bandwidth for the bandwidth resources. As a result, according to the present embodiment, only the minimum necessary bandwidth to achieve the protection paths having the same bandwidth as the working paths is reserved for the protection paths, eliminating the need to reserve a larger bandwidth than necessary as would be the case with the prior art.

The number of shared paths P is not limited to one, but the ring network NT may be provided with a plurality of shared paths. That is, the shared path table T 4 may include entries for a plurality of shared paths, and a plurality of queues corresponding to the respective shared paths may be created.

The bandwidth control units 13 and/or 14 may provide priority among the plurality of shared paths according to the priorities of the working paths backed up by the respective shared paths. Then, in accordance with the thus provided priority, the bandwidth control units 13 and/or 14 may reduce the allowable bandwidth to be reserved for each shared path, i.e., the bandwidth of the traffic to be output from the queue used to control the traffic of the protection path that uses the bandwidth resources of the shared path.

More specifically, in accordance with the prescribed priority predetermined among the respective shared paths, the bandwidth control units 13 and/or 14 may reduce the allowable bandwidth to be reserved for each shared path to a value smaller than the maximum total bandwidth value determined for each shared path. For example, a coefficient may be predefined according to the priority in such a manner that the coefficient becomes smaller as the priority increases. Then, the bandwidth control units 13 and/or 14 may determine the allowable bandwidth to be reserved for each shared path, by multiplying the maximum total bandwidth value with the coefficient. The bandwidth control units 13 and/or 14 may fix the allowable bandwidth for a selected one of the plurality of shared paths.

In the above embodiment, the allowable bandwidth to be reserved for the shared path has been specified by the shared path setup command or the shared path change command from the NMS 10 . In the following embodiment, on the other hand, when a new working path is setup, each of the nodes N 1 to N 6 adaptively changes the allowable bandwidth to be reserved for the shared path.

FIG. 24 is an explanatory diagram illustrating an example of a method for changing the allowable bandwidth of the shared path in response to the setup of a new working path. In the illustrated ring network NT, working paths A and B having bandwidths of 50 Mbps and 100 Mbps, respectively, are set up. The working path A is set up from the startpoint node apparatus N 1 to the endpoint node N 2 by passing through the node apparatuses N 1 and N 2 in this order. The working path B is set up from the startpoint node apparatus N 3 to the endpoint node N 5 by passing through the node apparatuses N 3 , N 4 , and N 5 in this order. The maximum total bandwidth value is 100 Mbps which is used on the links L 3 and L 4 through which the working path B passes. Therefore, bandwidth resources equivalent to 100 Mbps are reserved for the shared path P.

Consider the case where an additional working path C having a bandwidth of 70 Mbps is set up here. The working path C is set up from the startpoint node apparatus N 6 to the endpoint node N 3 by passing through the node apparatuses N 6 , N 1 , N 2 , and N 3 in this order. When the working path C is set up, the maximum total bandwidth value is 120 Mbps which is used on the link L 1 where the working paths A and C overlap. It therefore becomes necessary to change the bandwidth resources of the shared path P from 100 Mbps to 120 Mbps.

In the present embodiment, tentative maximum bandwidth information is added in the instruction information contained in the working path setup message M. FIG. 25 is a diagram illustrating a second example of the data structure of the instruction information contained in the working path setup message. The node apparatus N 6 at the startpoint of the working path setup message M for setting up the working path C creates the working path setup message M. The node apparatus N 6 specifies as the value of the tentative maximum bandwidth information the sum of the bandwidths that the current working path and the new working path C respectively use on the link L 6 that is connected to the node apparatus N 6 and that lies along the route of the working path C. In the illustrated example, the value of the tentative maximum bandwidth information is 70 Mbps.

The working path setup message M from the node apparatus N 6 is received at the next node apparatus N 1 on the working path C. The node apparatus N 1 calculates the sum of the bandwidths that the current working path and the new working path C respectively use on the link L 1 that is connected to the node apparatus N 1 and that lies along the working path C. The sum is calculated as 50 Mbps+70 Mbps=120 Mbps. The node apparatus N 1 compares the sum with the tentative maximum bandwidth information contained in the working path setup message M received from the node apparatus N 6 , and takes the larger value as the value of the tentative maximum bandwidth information. The value of the tentative maximum bandwidth information is now 120 Mbps. The same processing is repeated at the next node apparatus N 2 on the working path C. The value of the tentative maximum bandwidth information remains at 120 Mbps.

The node apparatus N 3 at the endpoint of the working path C receives the working path setup message M from the node apparatus N 2 . The node apparatus N 3 compares the value of 120 Mbps carried as the tentative maximum bandwidth information in the received working path setup message M with the value of 100 Mbps currently specified as the allowable bandwidth in the queue table T 2 for the shared path P.

If the value of the tentative maximum bandwidth information contained in the received working path setup message M is larger than the allowable bandwidth currently specified in the queue table T 2 , the node apparatus N 3 updates the value of the allowable bandwidth, specified in the queue table T 2 for the shared path P, to the value of the tentative maximum bandwidth information. In the present embodiment, since the value of the tentative maximum bandwidth information, 120 Mbps, is larger than the currently specified allowable bandwidth value of 100 Mbps, the value of the allowable bandwidth specified in the queue table T 2 for the shared path P is updated to 120 Mbps.

At this time, a shared path change message for changing the value of the allowable bandwidth requested of the shared path P to the value of the tentative maximum bandwidth information is transmitted from the node apparatus N 3 to the node apparatus N 2 that transmitted the working path setup message to the node apparatus N 3 . When creating the shared path change message, the node apparatus N 3 includes therein the routing information that specifies the route that passes through the node apparatuses N 3 , N 2 , N 1 , N 6 , N 5 , N 4 , and N 3 in this order. With this specification, the shared path change message is transmitted to all the node apparatuses N 1 to N 6 , and the value of the allowable bandwidth specified in the queue table T 2 for the shared path P is updated to 120 Mbps at each of these node apparatuses.

Further, a protection path setup message for setting up a new protection path C′ used to back up the working path C is transmitted from the node apparatus N 3 to the node apparatus N 2 that transmitted the working path setup message to the node apparatus N 3 . In the protection path setup message, the node apparatus N 3 specifies the shared path P as the shared path whose bandwidth resources are to be used by the protection path C. When creating the protection path setup message, the node apparatus N 3 includes therein the routing information that specifies the route that passes through the node apparatuses N 3 , N 2 , N 1 , N 6 , N 5 , N 4 , and N 3 in this order. With this specification, the new protection path C′ that transmits the signal in the opposite direction to the signal transporting direction of the working path C is set up so as to cycle around the ring network NT.

FIG. 26 is a flowchart illustrating one example of the processing that the node apparatus N 1 performs in response to the reception of the working path setup message in accordance with the method of FIG. 24 for changing the allowable bandwidth of the shared path. In step S 70 , the node apparatus N 1 receives the working path setup message. For convenience of explanation, it is assumed that the new path to be set up by this working path setup message is a path that transmits the signal in the clockwise direction around the network NT as depicted in FIG. 24 .

In step S 71 , based on the routing information contained in the received working path setup message, the working path message processing unit 41 determines whether the node apparatus 1 is the endpoint node of the working path setup message. If the node apparatus 1 is the endpoint node (Y in step S 71 ), the working path message processing unit 41 proceeds to step S 76 . If the node apparatus 1 is not the endpoint node (N in step S 71 ), the working path message processing unit 41 proceeds to step S 72 .

In step S 72 , the working path message processing unit 41 calculates the sum of the bandwidths that the existing working path and the new working path respectively use on the link L 1 which is connected to the node apparatus N 1 , and whose upstream node of the new working path is the node apparatus N 1 . In step S 73 , the working path message processing unit 41 compares the sum calculated in step S 72 with the value of the tentative maximum bandwidth information contained in the received working path setup message.

If the sum calculated in step S 72 is not larger than the value of the tentative maximum bandwidth information (N in step S 73 ), the working path message processing unit 41 proceeds to step S 75 . If the sum calculated in step S 72 is larger than the value of the tentative maximum bandwidth information (Y in step S 73 ), then in step S 74 the working path message processing unit 41 updates the value of the tentative maximum bandwidth information to the sum calculated in step S 72 . After that, the working path message processing unit 41 proceeds to step S 75 .

In step S 75 , the working path message processing unit 41 transmits the working path setup message to the next node apparatus N 2 by including therein the sum calculated in step S 72 or the value of the received tentative maximum bandwidth information, whichever is larger, as the tentative maximum bandwidth information.

In step S 76 , the working path message processing unit 41 compares the value of the tentative maximum bandwidth information contained in the received working path setup message with the allowable bandwidth currently specified in the queue table T 2 for the shared path. If the value of the tentative maximum bandwidth information contained in the received working path setup message is not larger than the currently specified allowable bandwidth (N in step S 76 ), the node apparatus N 1 proceeds to step S 80 .

If the value of the tentative maximum bandwidth information contained in the received working path setup message is larger than the currently specified allowable bandwidth (Y in step S 76 ), the working path message processing unit 41 proceeds to step S 77 . In step S 77 , the working path message processing unit 41 updates the value of the allowable bandwidth, currently specified in the queue table T 2 for the shared path, to the value of the tentative maximum bandwidth information contained in the received working path setup message.

In step S 78 , the shared path message processing unit 40 creates a shared path change message for changing the value of the shared bandwidth reserved for the shared path to the value of the tentative maximum bandwidth information contained in the received working path setup message. When creating the shared path change message, the shared path message processing unit 40 includes therein the routing information that cycles around the ring network in the opposite direction to the direction of the new working path being set up. In step S 79 , the control message transmitting unit 22 transmits the shared path change message created in step S 78 to the adjacent node apparatus that transmitted the working path setup message.

In step S 80 , the protection path message processing unit 42 creates a protection path setup message for setting up a new protection path used to back up the new working path being set up. In the protection path setup message, the protection path message processing unit 42 specifies the shared path whose bandwidth resources are to be used by the protection path. When creating the protection path setup message, the protection path message processing unit 42 includes therein the routing information that cycles around the ring network in the opposite direction to the direction of the new working path being set up. In step S 81 , the control message transmitting unit 22 transmits the shared path change message created in step S 80 to the adjacent node apparatus that transmitted the working path setup message.

According to the present embodiment, when a change occurs in bandwidth usage due to the setting of a new working path, each node apparatus can automatically change the shared path bandwidth without the NMS 10 , etc. having to perform setup operations.

While the above embodiment has dealt with the case where the allowable bandwidth of the shared path is changed when a working path is set up, it will also be recognized that the allowable bandwidth of the shared path may be reduced in a similar manner when a working path is deleted.

According to the apparatus, system, and method discussed herein, the utilization efficiency of bandwidth resources improves because the wasteful reservation of bandwidth resources, which would arise if a protection path were provided independently for each of a plurality of working paths, can be avoided.

All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiment(s) of the present inventions have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.