JP3775925B2 - Fault recovery method and node in optical wavelength division multiplexing network - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a failure recovery method and apparatus in an optical wavelength division multiplexing network.
An optical wavelength division multiplexing network is an optical communication network comprising a plurality of nodes each incorporating an optical cross-connect device, and a plurality of optical transmission lines (links) that connect the nodes to form a network as a whole. And, when looking at the plurality of optical fibers constituting each of the optical transmission lines, a plurality of optical signals of various wavelengths are multiplexed and transmitted in each of the optical fibers. It is an optical communication network. Therefore, if optical signals of N types of wavelengths are transmitted simultaneously in each optical fiber, N times the number of conventional optical paths in SDH networks and ATM networks using single wavelength optical signals. The number of optical paths is ensured, and the transmission capacity increases dramatically. Here, N can take a value of 8 or more, for example.
[0002]
On the other hand, failure recovery refers to another normal optical path that replaces multiple optical paths that are disconnected due to a failure when a failure such as disconnection occurs in any node or link in the optical communication network. This means that a detour route that can secure the network is searched, and the original optical communication is restored through the detour route.
The present invention describes the above-described failure recovery in an optical wavelength division multiplexing network.
[0003]
[Prior art]
FIG. 23 is a diagram for explaining general failure recovery in an optical communication network. In this figure, reference numeral 1 denotes an optical communication network, and this optical communication network 1 is composed of a plurality of nodes 2 and links 3 connecting the adjacent nodes 2. Each node 2 incorporates an optical cross-connect device, and a desired optical path is formed between the links. The link 3 is composed of an optical transmission line, and the optical transmission line is composed of an optical fiber.
[0004]
In this figure, nine nodes 1 (A, B, C... I) are illustrated as an example, and it is assumed that a node failure has occurred in the central node 2-E, for example. Then, each node 2 (B, D, F, H) adjacent to the node 2-E detects a so-called LOS (Loss of Signal). In this example, it is assumed that among these nodes 2 (B, D, F, H), the node 2-D has become a failure detection node by a predetermined arrangement. Here, the node 2-D, which is a failure detection node, becomes a sender node and activates failure recovery.
[0005]
The sender node 2-D creates a failure recovery message for this purpose and broadcasts it to a plurality of counterpart nodes. It should be noted that which node is selected as a destination node is selected according to a predetermined agreement, and these are referred to as chooser nodes. In the example of this figure, nodes 2-B, 2-F and 2-H are chooser nodes. The flow of the failure recovery message broadcast to these chooser nodes is represented by arrows drawn along each link 3 in the figure.
[0006]
Each chooser node that has received the failure recovery message sends an unused optical path or spare optical path that it has for the outgoing link to the downstream node, and finally sends it to the sender node. Return to node 2-D.
When the node 2-E that has caused the node failure searches for an optical path that can replace the optical path held until immediately before the node failure by broadcasting the failure recovery message, these alternative optical paths are used. The detour route is set and the failure recovery is completed.
[0007]
[Problems to be solved by the invention]
The above-described failure recovery method by broadcasting a failure recovery message is a technique established in general SDH networks and ATM networks.
However, in the optical wavelength division multiplexing network targeted by the present invention, the optical path form (multiple wavelength) is completely different from the optical path form (single wavelength) in a general SDH network or ATM network. There is a first problem that the intended failure recovery cannot be performed unless the failure recovery method is significantly changed.
[0008]
In addition, there is a second problem as follows. This second problem is due to the fact that the above optical wavelength division multiplexing communication is performed under one or both of the two modes. The first mode is a WP (Wavelength Path) mode, and the second mode is a VWP (Virtual Wavelength Path) mode. When focusing on one optical path, the WP mode is a mode that uses the same wavelength from the start point to the end point of this optical path. Such a WP mode is employed when no node through which the path passes has a wavelength converter. On the other hand, in the VWP mode, focusing on one optical path, the wavelength is changed for each node from the start point to the end point of this optical path. Such a VWP mode is employed when at least one of the nodes through which the path passes includes a wavelength converter. From the viewpoint of substantial increase in transmission capacity, the VWP mode is naturally more advantageous than the WP mode. However, the above wavelength converter is very expensive at present. For this reason, at present, it is usual to provide wavelength converters only at important nodes such as hub nodes.
[0009]
Thus, the second problem is that both the WP mode and the VWP mode must be supported in performing the failure recovery.
Therefore, in view of the first and second problems, the present invention can cope with a plurality of types of optical paths using different wavelengths, and can cope with one or both of the WP mode and the VWP mode. It is an object of the present invention to provide a failure recovery method and apparatus in an optical wavelength division multiplexing communication network.
[0010]
[Means for Solving the Problems]
FIG. 1 is a format diagram showing one frame of a failure message according to the present invention. The failure recovery message shown in FIG. 23 has the frame format shown in FIG. 1 in the present invention.
The failure recovery method of the present invention using the failure message MS of FIG. 1 is implemented as follows. That is, in an optical wavelength division multiplexing communication network including a plurality of nodes 2 and a plurality of links 3 that connect adjacent nodes 2, when a failure occurs in any of the nodes or links, one node changes to the other. By broadcasting the failure recovery message to the node, a detour route that replaces the optical path that was interrupted by the failure is searched for and the failure is recovered.
[0011]
Here, the above-described failure recovery message is composed of at least three tables 11, 12, and 13, more preferably two tables 14 and 15. In the remaining area, other information required for failure recovery is recorded. The contents of the first table 11 to the third table 13 are as follows.
The first table 11 indicates the path ID indicating the type of the optical path that has been cut off due to the failure, the type of wavelength used by each optical path, and the number of wavelengths required for each of the different wavelengths. The number of wavelength requests is recorded for each type of the optical path.
[0012]
The second table 12 records a destination that designates at least one node (a chooser node) to which the failure recovery message MS is to be sent.
The third table 13 records the number of usable wavelengths indicating the number of usable wavelengths in the link 3 on the upstream side of each node 2 that has received the failure recovery message MS for each wavelength.
[0013]
Here, each node 2 that receives the failure recovery message MS
An allowable wavelength memory (described later) that stores the allowable number of wavelengths that can be used in the downstream link 3 for each of various wavelengths, and the number of wavelengths that can be used in the received failure recovery message MS. Referring to the third table 13 to be recorded, the number of usable wavelengths is compared with the number of usable wavelengths, and the number of usable wavelengths in the third table 13 is rewritten with the smaller number. The message MS is sent to the link 3 on the downstream side.
[0014]
Further, the above-described tables 14 and 15, that is, the fourth table and the fifth table will be described.
The fourth table 14 is useful in the following cases. In other words, at least a WP (Wavelength Path) mode node 2 is included in the optical wavelength division multiplexing network 1, and the wavelength input from the upstream link 3 at the node 2 is temporarily passed through the electrical cross-connect device. This is a case where optical / electrical conversion for converting to another wavelength is performed by returning to the optical cross-connect device again.
[0015]
Here, the fourth table 14 records the number of times of optical / electrical conversion indicating the number of times that the optical / electrical conversion has been performed, and a predetermined number of optical / electrical conversions that limit the total number of times the optical / electrical conversion is performed. To do.
The fifth table 15 is useful in the following cases. That is, the optical wavelength division multiplexing network 1 has at least a node 2 in the VWP (Virtual Wavelength Path) mode, and converts the wavelength input from the upstream link 3 in the node 2 to an arbitrary wavelength and converts it to the downstream side. This is a case of outputting to the link 3 of FIG.
[0016]
Here, the fifth table 15 is a usable wavelength indicating the number of all wavelengths that can be used in the link 3 on the upstream side of the node that has received the failure recovery message MS, and the node ID that identifies the wavelength-converted node. Record the total number as well as the total number of usable wavelengths after optical / electrical conversion indicating the number of all wavelengths available when optical / electrical conversion is performed.
[0017]
The present invention records at least the contents of the first table 11 to the third table 13 as the contents of the failure message MS, and further records the contents of the fourth table 14 and the fifth table 15, thereby enabling the optical wavelength division multiplexing network 1 to be recorded. It is possible to easily and quickly perform a detour route search at the time of failure.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 2 is a format diagram showing a specific example of the first table 11.
Referring to FIG. 23, since a failure has occurred in node 2-E, there is a break between node 2-B and node 2-E and between node 2-E and node (referred to as a sender node) 2-D. It is necessary to recover at least one optical path. In FIG. 2, the first optical path OP1 and the second optical path OP2 are shown as an example of the optical path that is cut off. For each, the path ID, the type of wavelength (λ1, λ2, λ3... Λn), and the number of required wavelengths, that is, the number of requests, are recorded. Normally, there is usually only one optical signal of one wavelength, but when one optical path is composed of several optical fibers, there are a plurality of optical signals of the same wavelength.
[0019]
FIG. 3 is a format diagram showing a specific example of the second table 12. In the example of this figure, two destinations are shown. These destinations are chooser nodes, such as node 2-B and node 2-H shown in FIG.
FIG. 4 is a format diagram showing a specific example of the third table 13. In each node 2 that has received the failure message MS, the number of wavelengths that can be used in the link 3 on the upstream side, that is, the number that can be used, is recorded here. In the example of this figure, each usable number for wavelengths λ1 and λ2 is shown. This usable number is naturally the number of unused wavelengths or wavelengths that are not used as reserves. Therefore, referring again to FIG. 23, the contents of the third table 13 in the first failure message MS broadcast from the sender node Node 2-D to the Node 2-A side and broadcast to the Node 2-G side. The contents of the third table 13 in the second failure message MS to be set are set separately.
[0020]
FIG. 5 is a format diagram showing a specific example of the fourth table 14. The fourth table 14 records the number of optical / electrical conversions and the number of optical / electrical conversion limits described above.
If the node is in the VWP mode, an arbitrary wavelength can be transmitted from the output port of any of the wavelengths λ1, λ2,... Λn input to the input port. However, in a node in the WP mode, if the wavelength input to the input port is λ1, the wavelength from the output port is also limited to λ1. If it does so, the freedom degree for satisfy | filling the request | requirement shown by the 1st table 11 will become small significantly.
[0021]
Therefore, it is convenient if the optical cross-connect device and the electrical cross-connect device in each node are linked so that λ2 is obtained as the wavelength on the output port side even if the wavelength input to the input port is λ1. In this case, wavelength conversion of λ1 → λ2 can be performed by optical / electrical conversion by these devices.
FIG. 6 is a diagram illustrating an example of an apparatus that performs optical / electrical conversion. In this figure, reference numeral 5 denotes an optical cross-connect device, which is an essential device in each node 2. This optical cross-connect device 5 has a switch SW for path conversion arranged between the inter-station interfaces 7 and between the intra-station interfaces 8. The electrical cross-connect device 6 also has substantially the same configuration as the optical cross-connect device 5.
[0022]
Assuming that the wavelength λ1 is received at the input-side interoffice interface 8 of the optical cross-connect device 5 and the wavelength λ2 is output from the output-side interoffice interface 8, direct conversion from λ1 to λ2 under the VW mode Therefore, the output of the switch SW of the optical cross-connect device 5 is once dropped on the electrical cross-connect device 6 via the intra-office interface 8 and then returned to the optical cross-connect device 5 via the intra-office interface 8 again. λ2 is output to the output side inter-station interface 7 of the apparatus 5. Thus, the optical / electrical conversion is performed.
[0023]
FIG. 7 is a format diagram showing a specific example of the fifth table 15. In the fifth table, the node ID for identifying the node on which wavelength conversion has been performed, that is, the conversion node ID, and the number of all wavelengths that can be used in the link 3 upstream of the node that has received the message MS, Record the total number of wavelengths available. However, the contents may be rewritten when the message MS passes through the node.
[0024]
FIG. 8 is a diagram showing a configuration example of one node in the optical wavelength division multiplexing network based on the present invention.
In this figure, the node 2 includes at least an optical cross-connect device 5, overhead processing means 20, and failure recovery processing means 30.
The optical cross-connect device 5 sets a path for an optical signal input via the input side link 3in connecting between adjacent nodes, and passes this to the corresponding output side link 3out via the output side interface package 18. Switch.
[0025]
The overhead processing means 20 extracts an overhead part from the optical signal input via the input side link 3in and the input side interface package 17, rewrites the information in the overhead, and sends it to the output side link 3out.
The failure recovery processing means 30 performs processing for failure recovery based on the information in the overhead extracted by the overhead processing means 20 and rewrites the information in the overhead based on the processing result. Causes the optical cross-connect device 5 to set a path.
[0026]
Here, the information in the overhead includes the above-described failure recovery message MS, and the failure recovery message MS includes at least
(I) a path ID indicating the type of an optical path that has been cut off due to a failure, a type of wavelength used by each optical path, and a number of wavelength requests indicating the number of wavelengths required for each wavelength. For each optical path type, the first table 11 (FIG. 1) described above,
(Ii) the above-described second table 12 (FIG. 1) for recording a destination designating at least one node (tuser node) to which the failure recovery message MS is to be sent;
(Iii) The above-described third table 13 that records the number of usable wavelengths indicating the number of wavelengths that can be used in the upstream ingress link 3in of each node 2 that has received the failure recovery message MS for each wavelength. 1).
[0027]
The node 2 in FIG. 8 further includes a management information database (MIB) 40, which searches for a detour path that replaces the optical path that was interrupted by a failure that occurred in the optical wavelength division multiplexing network 1. System information in the communication network 1 necessary for recovering the failure is collected in advance and held in a rewritable manner, and information is exchanged with the failure recovery processing means 30.
[0028]
In FIG. 8, the memory means as described above includes an allowable wavelength memory, a failure recovery memory, a path memory, and the like. These are accommodated in the failure recovery processing means 30 described above, for example. In FIG. 8, these are shown as an allowable wavelength memory (MEM1) 31, a failure recovery memory (MEM2) 32, and a path memory (MEM3) 33. The permissible wavelength memory 31 stores the permissible wavelength number of wavelengths allowed to be used in the downstream output side link 3out for each of various wavelengths.
[0029]
Further, the failure recovery memory 32 uses the number of wavelengths allowed to be used in the downstream outgoing link 3out and the upstream incoming link recorded in the third table 13 for each wavelength. The number of usable wavelengths indicating the number of usable wavelengths in 3 inches is compared, and the smaller number obtained from the comparison result is stored for each downstream outgoing link 3out.
[0030]
Looking further at the path memory 33, when the node 2 becomes a sender node that starts fault recovery, the path memory 33 of this sender node stores the WP mode and VWP for each chooser node that is the destination of the fault recovery message MS. Information indicating the mode type and information indicating the wavelength of the input port and the wavelength of the output port are stored.
[0031]
When the node shown in FIG. 8 is a WP (Wavelength Path) mode node, optical / electrical conversion is performed to temporarily convert the wavelength input from the upstream ingress link 3in into another wavelength. It has an electrical cross-connect device that returns to the optical cross-connect device again. This is shown as block 5 in FIG.
The failure recovery message MS records the number of times of optical / electrical conversion indicating the number of times that the above optical / electrical conversion has been executed, and a predetermined number of optical / electrical conversions that limit the total number of executions of the optical / electrical conversion. The fourth table 14 is particularly related to the node 2 in the WP mode.
[0032]
On the other hand, when the node 2 shown in FIG. 8 is a node in the VWP (Virtual Wavelength Path) mode, the wavelength input from the upstream ingress link 3in is converted into an arbitrary wavelength, and the downstream egress link 3out is output. A wavelength converter for outputting to This is shown as a wavelength converter 19.
In the failure recovery message MS, the node ID that identifies the wavelength-converted node, the total number of usable wavelengths indicating the number of all wavelengths that can be used in the upstream ingress link 3in, and the optical / electrical conversion are executed. In this case, the fifth table 15 for recording the total number of usable wavelengths after optical / electrical conversion indicating the number of all wavelengths that can be used is included. This fifth table 15 is particularly suitable for the node 2 in the VWP mode. Involved.
[0033]
Next, a specific operation example will be described.
FIG. 9 is a diagram showing one model of nodes and links used for explaining the operation example. The node K in this figure is an arbitrary one of the plurality of nodes 2 shown in FIG. Also, one incoming link 3in and two outgoing links 3out are shown and named link I, link II and link III.
[0034]
FIG. 10 is a flowchart (part 1) showing an operation example of the node shown in FIG.
FIG. 11 is the same figure (the 2).
Referring to FIG. 10 and FIG. 11, steps S2 to S11 except for step S1 are commonly applied regardless of whether node 2 (FIG. 9) is a sender node or a chooser node. Step S1 when the node 2 is a chooser node is as shown in FIG. 10, but step S1 when the node 2 is a sender node replaces the step S1 shown in FIG. It is a “create as shown in step 1” step.
[0035]
In step S1 of FIG. 10, the node 2 reads the contents of the usable wavelength table 13 in the received message MS. This is performed between the overhead processing means 20 and the failure recovery processing means 30 in FIG.
FIG. 12 is a diagram showing a part in the message MS received by the node 2 from the link I in FIG. According to the numerical example shown here, the usable numbers of λ1 and λ2 (see FIG. 4) are 3 and 2, respectively. Further, the total number of required wavelengths (the total number of required numbers in the table 11 in FIG. 2) is 10 as an example.
[0036]
In step S2 of FIG. 10, the processing means 30 (FIG. 8) selects the transmission link (link II and / or link III of FIG. 9). For example, first select link II.
In step S3 of FIG. 10, the processing means 30 reads the contents of the allowable wavelength memory 31 (FIG. 8) for the link II. This content can also be extracted from the database 40.
[0037]
FIG. 13 is a diagram showing an example of the contents of the allowable wavelength memory. Regarding link II, it is allowed to use up to 5 for λ1.
In step S4 in FIG. 10, the number (3) in FIG. 12 is compared with the number (5) in FIG. 13, and the smaller number (3) is used in the usable wavelength table 13 of the new message MS sent to the link II. To record. For λ2, the smaller 0 is obtained by comparing 2 and 0.
[0038]
In step S5 of FIG. 10, the total number of usable wavelengths in the usable wavelength table 13 (FIG. 4) in the new message MS is compared with the requested number of wavelengths shown (“10” in FIG. 12).
If the required number of wavelengths is smaller in step S6 of FIG. 11 (NO), the next link III is selected in step S11.
[0039]
If the required number of wavelengths is larger in step S6 (YES), the process proceeds to step S7.
In step S7, the fourth table in FIG. 5 is referred to.
FIG. 14 is a diagram showing a numerical example of the optical / electrical conversion table 14. According to this numerical example, the limit number 1 is not reached and optical / electrical conversion is possible.
[0040]
In step S8 of FIG. 11, the allowable number of wavelengths of the link II is checked as 5, and in step S9, 5-3 = 2 can be newly used by optical / electrical conversion.
In step S10, the optical / electrical conversion table 15 in the new message MS is rewritten, and finally the message shown in FIG. 15 is sent to the link II.
FIG. 15 is a diagram showing a part of the message MS sent to the link II in FIG. The sum of the originally usable number 3 (λ1) and the number 2 (λ1) added by the optical / electrical conversion is 5 (λ1) shown in FIG.
[0041]
Of the operations described above, step S4 can be expressed in a more generalized manner. The processing unit 30 stores the smaller number in the built-in failure recovery memory 32 (FIG. 8) in the downstream link (link II, Stored for each link III), temporarily reserve a wavelength corresponding to the smaller number, and then send the rewritten failure recovery message MS downstream.
[0042]
When the processing unit 30 confirms that the confirmation message for the failure recovery message MS has been returned from the downstream side toward the sender node that started the broadcast of the failure recovery message, the processing means 30 performs the above temporarily reserved small one. This reservation is made for the wavelength corresponding to the number of optical paths, and an optical path that forms a detour path is set.
Further, of the above-described operations, the processing means 30 can express the useable wavelength number stored in the allowable wavelength memory 31 as the number of usable wavelengths recorded in the third table 13 by further generalizing the processing after step S7. If it is confirmed that wavelength conversion by optical / electrical conversion is possible, the number of optical / electrical conversions and the optical / electrical conversion limit number in the fourth table 14 are compared, and the former Is less than the latter, 1 is added to the number of times of optical / electrical conversion, and 1 is added to the usable number corresponding to the wavelength after wavelength conversion in the third table 13. Is sent to link II on the downstream side.
[0043]
Further, when the allowable wavelength number stored in the allowable wavelength memory 31 is insufficient with respect to the usable wavelength number recorded in the third table 13, the processing means 30 further performs wavelength conversion by optical / electrical conversion. When the number of optical / electrical conversions in the fourth table 14 and the optical / electrical conversion limit number are compared, and the number of the former reaches the latter number, the number of optical / electrical conversions is calculated. 1 is added, and the failure recovery message MS is rewritten so that the number of usable wavelengths corresponding to the wavelength in the third table 13 is 0, and is further transmitted to the link II on the downstream side.
[0044]
FIG. 16 is a flowchart showing another operation example of the node shown in FIG. The above description with reference to FIGS. 10 to 15 has mainly been made with a focus on the existence of a node in the WP mode. However, the following description of the operation will be made with a focus on the existence of a node in the VWP mode. For example, the sender node and the chooser node are nodes in the VWP mode, or the intermediate nodes are nodes in the VWP mode.
[0045]
Referring to FIG. 16, steps S2 to S11 excluding step S1 are commonly applied regardless of whether the node 2 (FIG. 9) is a sender node or a chooser node. Step S1 when the node 2 is a chooser node is as shown in FIG. 16, but step S1 when the node 2 is a sender node replaces the step S1 shown in FIG. It is a “create as shown in step 1” step.
[0046]
In step S <b> 1 of FIG. 16, the node 2 that has received the failure recovery message MS adds the numerical values in the usable wavelength table 13 in this message MS by the processing means 30. Further, this added value is recorded again in the wavelength conversion table 15, and then the contents of the usable wavelength table 13 are initialized (reset to zero).
FIG. 17 is a diagram showing a part in the message MS received by the node 2 from the link I in FIG. Also
FIG. 18 is a diagram showing the contents of a table obtained by adding the numerical values in the table of FIG.
[0047]
Referring also to step S1 in FIG. 16, the total 4 (= 3 + 1) in the <a> column and the total 3 (= 2 + 1) in the <b> column in FIG. 17 are shown as new wavelength tables 15 in FIG. As recorded. Thereafter, the contents of the usable wavelength table 13 are initialized.
In step S2 of FIG. 16, the processing means 30 (FIG. 8) selects the transmission link (link II and / or link III of FIG. 9). For example, first select link II.
[0048]
In step S3 of FIG. 16, the processing means 30 reads the contents of the allowable wavelength memory 31 (FIG. 8) for the link II. This content can also be extracted from the database 40.
FIG. 19 is a diagram showing an example of the contents of the allowable wavelength memory. Regarding link II, it is allowed to use up to three for λ1.
[0049]
In step S3 in FIG. 16, the number (4) in FIG. 18 is compared with the number (3) in FIG. 19, and the smaller number (3) is used in the usable wavelength table of the new message MS sent to the link II. 13 is recorded. For λ2, the smaller of 2 in comparison of 2 and 3 is taken.
When transmission of the message MS to the transmission link I is completed, the next transmission link III shown in FIG. 9 is selected in step S4 of FIG.
[0050]
FIG. 20 is a diagram showing a part of the message MS sent through the processing flow of FIG. A table 13 in which the numbers determined in step S3 in FIG. 16 are recorded is shown.
When the operation described with reference to FIGS. 16 to 20 is further generalized and expressed, the processing unit 30 adds the number of usable wavelengths for each wavelength in the third table 13 and uses the total number to calculate the fifth table 15. The total number of usable wavelengths is rewritten, and all the usable wavelengths in the third table 13 are initialized to zero. Then, the failure recovery message MS is rewritten so that the allowable wavelength number stored in the allowable wavelength memory 31 is compared with the above total number, and the smaller number is used as the usable wavelength number in the third table. To link II.
[0051]
Further, the processing means 30 stores the contents of the rewritten failure recovery message MS in the built-in failure recovery memory 32, temporarily reserves the allocation of each wavelength with this content, and then downstream the rewritten failure recovery message MS. Send to side link II.
Thereafter, when the processing means 30 confirms that the confirmation message for the failure recovery message MS has been returned from the downstream side toward the sender node that started the broadcast of the failure recovery message MS, the provisional reservation described above is made. The wavelength allocation is fully reserved, and an optical path that forms a detour path is set.
[0052]
FIG. 21 is a diagram showing a part of the path memory 33. The path memory 33 is included in a part of the processing means 30 as shown in FIG. 8, but may be stored in the management information database 40 shown in FIG.
When the node 2 becomes a sender node that activates failure recovery, the path memory 33 of the sender node includes information indicating the type of the WP mode and the VWP mode for each chooser node that is the destination of the failure recovery message MS; Information indicating the wavelength of the input port and the wavelength of the output port is stored. This path memory 33 is useful for creating the recovery wavelength table (first table 11) shown in FIG.
[0053]
FIG. 22 is a diagram showing a model for explaining the path memory of FIG. Referring to FIGS. 21 and 22, the chooser node (N1) 2 forming the optical path OP1 is a node in the WP mode, so that both the input port and the output port handle the same wavelength. For example, λ1.
On the other hand, since the chooser node (N4) forming the optical path OP2 is in the VWP mode, even if the wavelength λ2 is inputted from the input port, all wavelengths can be taken at the output port.
[0054]
If attention is paid to the existence of such a path memory 33, the degree of freedom in searching for a detour route can be further increased.
When the node 2 becomes a sender node that starts failure recovery, for each chooser node that is the destination of the failure recovery message, information indicating the type of the WP mode and VWP mode, the wavelength of the input port, and the wavelength of the output port The path memory 33 for storing information is referred to. Depending on whether the chooser node is in the WP mode or the VWP mode, the wavelength in the first table 11 is set to the wavelength of the output port in the WP mode, and the wavelength in the first table 11 is set in the VWP mode. A failure message MS is set such that is set to all wavelengths used in the optical wavelength division multiplexing communication. In this way, since there are cases where the required wavelengths can be all wavelengths, the degree of freedom in wavelength selection increases.
[0055]
【The invention's effect】
As described above, according to the present invention, it is possible to search both the path and the wavelength to be used at the same time and at high speed in the detour path search when a failure occurs in the optical wavelength division multiplexing network. The search method is not limited to an optical communication network including only WP mode nodes or VWP mode nodes, but also to an optical communication network including a mixture of WP mode nodes and VWP mode nodes. Applicable.
[Brief description of the drawings]
FIG. 1 is a format diagram showing one frame of a failure message according to the present invention.
FIG. 2 is a format diagram showing a specific example of a first table 11. FIG.
FIG. 3 is a format diagram showing a specific example of the second table 12;
FIG. 4 is a format diagram showing a specific example of a third table 13;
FIG. 5 is a format diagram showing a specific example of a fourth table 14;
FIG. 6 is a diagram illustrating an example of an apparatus that performs optical / electrical conversion.
7 is a format diagram showing a specific example of a fifth table 15. FIG.
FIG. 8 is a diagram showing a configuration example of one node in an optical wavelength division multiplexing network based on the present invention.
FIG. 9 is a diagram showing one model of nodes and links used for explaining an operation example;
FIG. 10 is a flowchart (part 1) illustrating an operation example of the node illustrated in FIG. 9;
FIG. 11 is a flowchart (part 2) illustrating an operation example of the node illustrated in FIG. 9;
12 is a diagram showing a part in message MS received by node 2 from link I in FIG. 9;
FIG. 13 is a diagram illustrating an example of contents of an allowable wavelength memory.
14 is a diagram showing a numerical example of the optical / electrical conversion table 14. FIG.
FIG. 15 is a diagram showing a part of a message MS sent to link II in FIG. 9;
FIG. 16 is a flowchart illustrating another operation example of the node illustrated in FIG. 9;
FIG. 17 is a diagram showing a part in message MS received by node 2 from link I in FIG. 9;
18 is a diagram showing the contents of a table obtained by adding the numerical values in the table of FIG.
FIG. 19 is a diagram illustrating an example of contents of an allowable wavelength memory.
20 is a diagram showing a part of a message MS sent through the processing flow of FIG.
FIG. 21 is a diagram showing a part of the path memory 33;
FIG. 22 is a diagram illustrating a model for explaining the path memory of FIG. 21;
FIG. 23 is a diagram for explaining general failure recovery in an optical communication network.
[Explanation of symbols]
1 ... Optical communication network
2 ... Node
3 ... Link
3in ... incoming link
3out ... outgoing link
5. Optical cross-connect device
6 ... Electric cross-connect device
11 ... 1st table
12 ... Second table
13 ... Third table
14 ... Fourth table
15 ... Fifth table
19 ... Wavelength converter
20: Overhead processing means
30. Failure recovery processing means
31. Allowable wavelength memory (MEM1)
32 ... Fault recovery memory (MEM2)
33 ... Path memory (MEM3)
40 ... Management information database
MS ... Fault message
OP1, OP2 ... Optical path

Claims (18)

By providing a plurality of nodes and a plurality of links connecting the adjacent nodes, and when a failure occurs in any node or link, by broadcasting a failure recovery message from one node to another node In a failure recovery method in an optical wavelength division multiplexing network that searches for a detour path that replaces the optical path that was interrupted by the failure and recovers the failure,
The disaster recovery message is:
A path ID indicating the type of the optical path that has been interrupted by the failure, a type of wavelength used by each optical path, and a wavelength request number indicating the number of wavelengths required for each of the different wavelengths. A first table for recording each type of the optical path;
A second table recording a destination designating at least one of the nodes to which the disaster recovery message is to be sent;
A third table that records, for each wavelength, the number of usable wavelengths indicating the number of wavelengths that can be used in the link on the upstream side of each node that has received the failure recovery message;
Comprising at least
Each of the nodes receiving the disaster recovery message
An allowable wavelength memory for storing the allowable number of wavelengths that can be used in the link on the downstream side for each of various wavelengths, and the number of usable wavelengths recorded in the received failure recovery message The number of usable wavelengths and the number of usable wavelengths are compared, and the number of usable wavelengths in the third table is rewritten with the smaller number by comparing the allowable number of usable wavelengths and the number of usable wavelengths. A fault recovery method in an optical wavelength division multiplexing communication network, characterized by transmitting to the downstream link. The optical wavelength multiplexing communication network has at least a WP (Wavelength Path) mode node, and the wavelength input from the link on the upstream side of the node passes through the electrical cross-connect device and then is optically crossed again. When performing optical / electrical conversion to convert to another wavelength by returning to the connect device,
The failure recovery message records the number of optical / electrical conversions indicating the number of times the optical / electrical conversion has been performed, and a predetermined number of optical / electrical conversion controls that limit the total number of optical / electrical conversions to be performed. The failure recovery method according to claim 1, further comprising a fourth table. The optical wavelength division multiplexing network has at least a node in the VWP (Virtual Wavelength Path) mode, and converts the wavelength input from the link on the upstream side to an arbitrary wavelength in the node and converts the wavelength to the link on the downstream side. When outputting,
The failure recovery message includes a node ID that identifies a node for which wavelength conversion has been performed, a total number of usable wavelengths indicating the number of all wavelengths that can be used in the link upstream of the node that has received the failure recovery message, and 2. The fifth table according to claim 1, further comprising a fifth table for recording a total number of usable wavelengths after optical / electrical conversion indicating the number of all wavelengths usable when optical / electrical conversion is performed. Disaster recovery method. The node stores the smaller number of the comparison in the built-in failure recovery memory for each link on the downstream side, temporarily reserves a wavelength corresponding to the smaller number, and then rewritten the wavelength. The failure recovery method according to claim 1, wherein a failure recovery message is sent downstream. When the node confirms that the confirmation message for the failure recovery message has been returned from the downstream side toward the one node that has started broadcasting the failure recovery message, the temporary reserved small The fault recovery method according to claim 4, wherein a wavelength corresponding to the number of the two is reserved and an optical path that forms the detour path is set. If the allowable wavelength number stored in the allowable wavelength memory is insufficient with respect to the usable wavelength number recorded in the third table, the node further performs wavelength conversion by the optical / electrical conversion. When the number of the optical / electrical conversions in the fourth table and the optical / electrical conversion limit number are compared and the number of the former is less than the latter, the optical / electrical conversion is confirmed. The failure recovery message is rewritten so that the number of conversions is incremented by 1 and the usable number corresponding to the wavelength after wavelength conversion in the third table is incremented by 1, and further sent downstream. Disaster recovery method. If the allowable wavelength number stored in the allowable wavelength memory is insufficient with respect to the usable wavelength number recorded in the third table, the node further performs wavelength conversion by the optical / electrical conversion. When the number of the optical / electrical conversions in the fourth table and the optical / electrical conversion limit number are compared, and the number of the former reaches the latter, the optical / electrical conversion is confirmed. The failure according to claim 2, wherein the number of conversions is incremented by 1 and the failure recovery message is rewritten so that the number of usable wavelengths corresponding to the wavelength in the third table is 0 and further sent downstream. Recovery method. The node adds the number of usable wavelengths for each wavelength in the third table, and rewrites the total number of usable wavelengths in the fifth table with the total number, and in the third table Initialize the number of usable wavelengths to 0, and then
The failure recovery message is rewritten so that the allowable wavelength number stored in the allowable wavelength memory is compared with the total number and the smaller number is used as the usable wavelength number in the third table. The failure recovery method according to claim 3, wherein the failure recovery method is sent to the side. The node stores the content of the rewritten failure recovery message in a built-in failure recovery memory, temporarily reserves the allocation of each wavelength with this content, and then sends the rewritten failure recovery message downstream. The failure recovery method according to claim 8, which is transmitted. When the node confirms that the confirmation message for the failure recovery message has been returned from the downstream side toward the one node that has started broadcasting the failure recovery message, the temporarily reserved wavelength The fault recovery method according to claim 4, wherein the reservation of the allocation of the optical path and the setting of the optical path forming the detour path are performed. A node of an optical wavelength division multiplexing network,
An optical cross-connect device that sets a path for an optical signal input via an ingress link connecting between adjacent nodes and switches this to the corresponding egress link;
Overhead processing means for extracting an overhead part from the optical signal input via the input side link, rewriting information in the overhead and sending the information to the output side link;
Based on the information in the overhead extracted by the overhead processing means, processing for failure recovery is performed. Based on the processing result, the information in the overhead is rewritten and the optical cross-connect device Fault recovery processing means for executing the path setting for
Here, the information in the overhead includes a failure recovery message, and the failure recovery message includes at least a path ID indicating the type of the optical path that has been cut off due to the failure, and the type of wavelength used by each optical path. A first table that records, for each type of optical path, a wavelength request number indicating the number of wavelengths required for each of the different wavelengths;
A second table recording a destination designating at least one of the nodes to which the disaster recovery message is to be sent;
A third table that records, for each wavelength, the number of usable wavelengths indicating the number of wavelengths that can be used in the incoming link upstream of each node that has received the failure recovery message. A node of an optical wavelength division multiplexing network. The node is a node in a WP (Wavelength Path) mode, and performs optical / electrical conversion for once converting the wavelength input from the incoming link on the upstream side into another wavelength, and again forms an optical cross-connect. Having an electrical cross-connect device back to the device,
The failure recovery message records the number of optical / electrical conversions that represents the number of times that the optical / electrical conversion has been executed, and a predetermined optical / electrical conversion limit number that limits the total number of times the optical / electrical conversion has been performed. The node according to claim 11, wherein the node further includes a fourth table. The node is a node in a VWP (Virtual Wavelength Path) mode, and converts the wavelength input from the input link on the upstream side into an arbitrary wavelength and outputs the wavelength to the output link on the downstream side Have a bowl,
In the failure recovery message, a node ID that identifies a node that has performed wavelength conversion, a total number of usable wavelengths indicating the number of all wavelengths that can be used in the incoming link on the upstream side, and optical / electrical conversion are executed. The node according to claim 11, wherein the message further includes a fifth table that records a total number of usable wavelengths after optical / electrical conversion indicating the number of all wavelengths that can be used. The node searches in advance for an alternative path to the optical path that was interrupted by the failure that occurred in the optical wavelength division multiplexing network, and previously collected system information in the optical wavelength division multiplexing network that is necessary to recover the failure. The node according to claim 11, further comprising a management information database that is held in a rewritable manner and exchanges information with the failure recovery processing means. The node according to claim 11, wherein the failure recovery processing unit includes a permissible wavelength memory that stores the permissible wavelength number of the wavelength permitted to be used in the outgoing side link on the downstream side for each different wavelength. . The failure recovery processing means includes an allowable number of wavelengths allowed to be used in the downstream outgoing link and the upstream upstream input recorded in the third table for each wavelength. 12. A failure recovery memory comprising a failure recovery memory that compares the number of usable wavelengths indicating the number of usable wavelengths in a side link and stores the smaller number obtained from the comparison result for each downstream side outgoing link. The listed node. The failure recovery processing means includes a path memory, and when the node is a sender node that activates the failure recovery, the path memory of the sender node includes, for each chooser node that is the destination of the failure recovery message, the The node according to claim 11, wherein information indicating a type of the WP mode and the VWP mode and information indicating a wavelength of the input port and a wavelength of the output port are stored. The failure recovery processing means includes a path memory, and when the node is a sender node that activates the failure recovery, the path memory of the sender node includes, for each chooser node that is the destination of the failure recovery message, the Information indicating the type of the WP mode and the VWP mode, and information indicating the wavelength of the input port and the wavelength of the output port are stored in the path memory,
Depending on whether the chooser node is in the WP mode or the VWP mode, the wavelength in the first table is set to the wavelength of the output port in the WP mode, and the first table in the VWP mode. The node according to claim 11, wherein the wavelength is set to all wavelengths used in the optical wavelength division multiplexing communication.

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