Wavelength defragmentation device, wavelength defragmentation method, and program

Abstract

The wavelength defragmentation device according to the present invention performs wavelength reallocation for paths in an optical transmission network and includes a storage unit that stores a path information DB and a wavelength allocation management DB, and a wavelength defragmentation functional unit that refers to the path information DB for an attribute of a path and performs wavelength reallocation for the path having the attribute through an operation corresponding to the attribute.

Description

[Technical field]

[0001] The present invention relates to a technique for reallocating optical paths by wavelength defragmentation in the wavelength design of an optical transmission network. [Background technology]

[0002] In an optical transmission network, communication data is handled by light, and communication demands in the optical transmission network are called lightpaths. Lightpaths are accommodated in wavelengths available in optical fibers, but it is necessary to assign the same wavelength to a lightpath from the start node to the end node, which is called the wavelength continuity constraint.

[0003] When accommodating multiple optical paths at each wavelength within an optical fiber to satisfy this wavelength continuity constraint, a fragmented state can occur due to bias in the start and end nodes of the optical paths and repeated generation and removal of optical paths over the long-term operation of the optical transmission network, which can reduce the efficiency of wavelength utilization.

[0004] In order to improve the efficiency of wavelength usage, wavelength defragmentation (wavelength reallocation) methods are being considered. As a conventional technique, Non-Patent Document 1 discloses a defragmentation method that reduces the maximum wavelength number in use by changing the route.

[0005] The above "reduction of the maximum wavelength number in use" means that when optical paths are reallocated by defragmentation, they are reallocated to wavelengths with smaller wavelength numbers. Wavelength allocation, which assigns optical paths to new wavelengths, is generally done according to the First-Fit method (hereafter referred to as the FF method). Therefore, by performing operations to reduce the maximum wavelength number in use during defragmentation, fragmentation is less likely to occur when new optical paths are later assigned, which has the effect of improving wavelength utilization efficiency. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] Ankitkumar N. Patel, Philip N. Ji, Jason P. Jue, TingWan, "Defragmentation of Transparent Flexible Optical WDM (FWDM) Networks", in Proc. OFC 2011. Summary of the Invention [Problem to be solved by the invention]

[0007] In recent years, the types of communication services have become more diverse, and lightpaths with various quality classes exist according to the required quality of the services.

[0008] In conventional technology, the attributes of optical paths are not taken into consideration, so wavelength defragmentation using route changes is performed uniformly on all optical paths. Therefore, there is a possibility that the quality of optical paths may be impaired by wavelength defragmentation. In addition, there may be optical paths for which wavelength defragmentation is not possible in order to satisfy the required quality of the optical paths, so it is difficult to improve the wavelength accommodation efficiency by wavelength defragmentation.

[0009] For example, paths that accommodate highly reliable services that cannot tolerate interruptions in service cannot be defragmented because interruptions would occur with conventional technology. Also, paths that accommodate services that require low-latency communication may suffer from a loss of service quality if the path is changed during defragmentation.

[0010] The present invention has been made in consideration of the above-mentioned points, and has an object to provide a technique for performing wavelength defragmentation in consideration of the attributes of an optical path. [Means for solving the problem]

[0011] According to the disclosed technique, there is provided a wavelength defragmentation device that performs wavelength reallocation for paths in an optical transmission network, comprising: A storage unit for storing a path information DB and a wavelength allocation management DB; a wavelength defragmentation function unit that refers to an attribute of a path from the path information DB and performs wavelength reallocation of a path having the attribute by an operation according to the attribute, the wavelength defragmentation functional unit, in wavelength reallocation to a highly reliable path, refers to the wavelength allocation management DB in ascending order of wavelength number to check whether wavelengths are continuously available up to the currently used wavelength, and selects the wavelength with the smallest wavelength number for which continuous available wavelengths can be secured as a reallocated wavelength; In wavelength reallocation for a low-latency path, the wavelength defragmentation function unit refers to the wavelength allocation management DB and the path information DB, checks whether wavelengths are available on the route of the low-latency path described in the path information DB, in ascending order of wavelength number, and selects the available wavelength with the smallest wavelength number as the wavelength to be reallocated. A wavelength defragmentation apparatus is provided. Effect of the Invention

[0012] According to the disclosed technology, it is possible to perform wavelength defragmentation taking into account the attributes of the optical path. [Brief description of the drawings]

[0013] [Figure 1] 1 is an overall configuration diagram of a system according to an embodiment of the present invention. [Diagram 2] FIG. 1 is a configuration diagram of a wavelength defragmentation device. [Diagram 3] 13 is a flowchart showing an overall operation. [Figure 4] 13 is a flowchart of a process for canceling a low-latency path and a normal path. [Diagram 5] 13 is a flowchart of a process for executing wavelength reallocation of a highly reliable path. [Figure 6] 13 is a flowchart of a process for executing wavelength reallocation of a low latency path. [Figure 7] 13 is a flowchart of a wavelength reallocation execution process for a normal path. [Figure 8] 13 is a flowchart of a path reroute and reallocation process. [Figure 9] FIG. 1 is a diagram showing an image of the overall configuration of an optical transmission network. [Figure 10] FIG. 1 is a diagram illustrating an image of wavelength allocation in an optical transmission network. [Figure 11] FIG. 13 is a diagram showing an example of a path information DB. [Figure 12] FIG. 13 is a diagram showing an image of a wavelength allocation management DB. [Figure 13]FIG. 13 is a diagram showing the usage status of wavelengths in a specific example of S20. [Figure 14] FIG. 13 is a diagram showing a path information DB in a specific example of S20. [Figure 15] FIG. 11 is a diagram showing the usage status of wavelengths in a specific example of S30. [Figure 16] FIG. 13 is a diagram showing a path information DB in a specific example of S30. [Figure 17] FIG. 13 is a diagram showing the usage status of wavelengths in a specific example of S40. [Figure 18] FIG. 13 is a diagram showing a path information DB in a specific example of S40. [Figure 19] FIG. 13 is a diagram showing the usage status of wavelengths in a specific example of S40. [Figure 20] FIG. 13 is a diagram showing a path information DB in a specific example of S40. [Figure 21] FIG. 2 illustrates an example of a hardware configuration of the apparatus. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an embodiment of the present invention (the present embodiment) will be described with reference to the drawings. The embodiment described below is merely an example, and the embodiment to which the present invention is applied is not limited to the following embodiment. In this embodiment, the "optical path" may be called a "path", "wavelength path", etc.

[0015] (Outline of the embodiment) In this embodiment, the wavelength defragmentation is performed while satisfying the required quality of the optical path by considering the attributes of the optical path and changing the wavelength reallocation method according to the attributes of the optical path. Specifically, different operations are performed for high-reliability paths that cannot tolerate interruptions in the path, low-delay paths with strict delay requirements, and normal paths with low required quality. However, the attributes of the optical path are not limited to these three types.

[0016] The configuration and operation of a system and device for implementing the above-mentioned wavelength defragmentation will now be described.

[0017] (System Configuration) An example of the overall configuration of a system according to the present embodiment is shown in Fig. 1. As shown in Fig. 1, the system includes a wavelength defragmentation device 100 and an optical transmission network 200.

[0018] The optical transmission network 200 is a backbone network, such as an IP communication network, that realizes communication by optical signals. The wavelength defragmentation device 100 is a device having the functions according to the present invention, and performs wavelength defragmentation (wavelength reallocation) processing on the optical transmission network 200.

[0019] The wavelength defragmentation device 100 may be a single physical device (computer) or may be configured by connecting a plurality of physical devices via a network. The wavelength defragmentation device 100 may also be a function provided on a cloud.

[0020] (Device configuration) 2 shows an example of the functional configuration of the wavelength defragmentation device 100. As shown in FIG. 2, the wavelength defragmentation device 100 has a wavelength defragmentation function unit 110, a storage unit 120, and an input / output function unit .

[0021] The wavelength defragmentation function unit 110 has a wavelength cancellation unit 111, a high reliability path defragmentation unit 112, a low latency path defragmentation unit 113, and a normal path defragmentation unit 114. The storage unit 120 has a path information DB 121 and a wavelength allocation management DB 122. The input / output function unit 130 has an input unit 131 and an output unit 132.

[0022] The above-mentioned functional configuration is merely an example, and functions and configurations other than those described above are not excluded. An overview of the operation of each unit in the wavelength defragmentation device 100 will be described below.

[0023] <Wavelength Defragmentation Function Unit 110> The wavelength canceling unit 111 cancels the assigned wavelength in accordance with attribute information in a path information DB 121, which will be described later.

[0024] The highly reliable path defragmentation unit 112 selects a wavelength reassignment destination of a path whose attribute is highly reliable based on information in a path information DB 121 and a wavelength assignment management DB 122 (to be described later), and replaces the path.

[0025] The low-latency path defragmentation unit 113 selects a wavelength reassignment destination of a path with a low-latency attribute based on information in the path information DB 121 and the wavelength assignment management DB 122, and replaces the path.

[0026] The normal path defragmentation unit 114 selects a wavelength reassignment destination and route for a path whose attribute is normal, based on information in the path information DB 121 and the wavelength allocation management DB 122, and replaces the path, including changing the route.

[0027] <Storage section 120> The path information DB 121 stores path information such as wavelength path IDs, allocation information, route information, service attributes, wavelength numbers assigned to wavelength paths, etc. The wavelength allocation management DB 122 stores the allocation status of wavelengths of each link constituting the optical transmission network 200.

[0028] <Input / output function unit 130> The input unit 131 inputs links to be wavelength reallocated, whether wavelength reallocation can be performed, etc. The output unit 132 outputs the execution results of each unit of the wavelength defragmentation device 100 and information of each DB of the storage unit 120.

[0029] (Overall operation) 3 is a flowchart showing the overall operation of the wavelength defragmentation device 100. In this embodiment, when a decrease in wavelength utilization efficiency of the entire optical transmission network 200 is detected by some means, the wavelength allocation management DB 122 and the path information DB 121 are set, and then the wavelength defragmentation device 100 is instructed to execute wavelength reallocation. The wavelength defragmentation device 100 that has been instructed to execute wavelength reallocation executes wavelength defragmentation processing for the optical transmission network 200 in accordance with the procedure of the flowchart shown in FIG.

[0030] In S10 (step 10), the wavelength cancellation unit 111 cancels the low-latency path and the normal path. In S20, the high-reliability path defragmentation unit 112 executes wavelength reallocation of the high-reliability path. In S30, the low-latency path defragmentation unit 113 executes wavelength reallocation of the low-latency path. In S40, the normal path defragmentation unit 114 executes wavelength reallocation of the normal path. Each of the operations S10 to S40 shown in FIG. 3 will be described with reference to a flowchart.

[0031] (S10: Cancellation of low latency path and normal path) 4 is a flowchart of the process of canceling a low-latency path and a normal path. In S11, the wavelength canceling unit 111 sequentially extracts path attribute information from the path information DB 121. In S12, if the path attribute is high reliability, the process proceeds to S14, and if not (i.e., if the attribute is a low-latency path and a normal path), the process proceeds to S13.

[0032] In S13, the wavelength cancellation unit 111 cancels paths whose attributes are low latency and normal, and releases the wavelengths used. When canceling a path, the allocation status in the path information DB 121 and the wavelength allocation management DB 122 are changed. If reference to all paths has been completed (YES in S14), the process proceeds to S20, and if there are any paths that have not been referenced (NO in S14), the process returns to S11 and performs the above process on another path.

[0033] (S20: Wavelength reassignment of reliable paths) 5 is a flowchart of the process of wavelength reassignment of a highly reliable path. A specific example based on the flowchart will be described later. In S21, the highly reliable path defragmentation unit 112 extracts the currently used wavelengths of the highly reliable paths from the path information DB 121, and in S22, creates a list in which the paths are sorted in ascending order of the used wavelength number.

[0034] In S23, the high-reliability path defragmentation unit 112 extracts paths from the top of the list in order. In S24, it selects wavelengths as reallocation candidates in order from the wavelength with the smallest wavelength number, and in S25, it determines whether or not the wavelengths of the route described in the path information DB 121 from the currently used wavelength to the reallocation destination wavelength are available. If the answer is Yes, it proceeds to S26, and if the answer is No, it returns to S24.

[0035] In S26, the high-reliability path defragmentation unit 112 reallocates paths to the reallocation destination wavelengths, and in S27 determines whether wavelength reallocation has been executed for all paths. If Yes, the process proceeds to S30, and if No, the process returns to S23.

[0036] (S30: Wavelength reassignment of low latency paths) 6 is a flowchart of the process of wavelength reallocation of low latency paths. A specific example based on the flowchart will be described later. In S31, the low latency path defragmentation unit 113 extracts the bandwidth of the low latency path from the path information DB 121, and in S32, creates a list in which the paths are sorted in descending order of path length and bandwidth.

[0037] In S33, the low latency path defragmentation unit 113 extracts paths from the top of the list in order, in S34 selects wavelengths as reallocation destination candidates in ascending order of wavelength number, and in S35 judges whether the wavelengths as reallocation destination candidates are available on the route described in the path information DB 121. If the answer is Yes, the process proceeds to S36, and if the answer is No, the process returns to S34.

[0038] In S36, the low latency path defragmentation unit 113 reallocates paths to the reallocated wavelengths, and in S37, determines whether wavelength reallocation has been executed for all paths. If Yes, the process proceeds to S40, and if No, the process returns to S33.

[0039] (S40: Wavelength reassignment of normal paths) 7 is a flowchart of the process of wavelength reallocation of normal paths. A specific example based on the flowchart will be described later. In S41, the normal path defragmentation unit 114 extracts the path length and bandwidth of the normal path from the path information DB 121, in S42, creates a list in which the paths are sorted in descending order of path length and bandwidth, and in S43, extracts paths from the top of the list.

[0040] In S44, the normal path defragmentation unit 114 selects candidate wavelengths for reallocation in ascending order of wavelength number, and in S45, determines whether the candidate wavelengths for reallocation are available on the route described in the path information DB 121. If Yes, proceed to S46, and if No, return to S44.

[0041] In S46, the normal path defragmentation unit 114 reallocates paths to the reallocation destination wavelengths, and in S47, it determines whether wavelength reallocation has been performed for all paths. If Yes, proceed to S48, and if No, return to S43. In S48, the path route is changed and reallocated. The path route change and reallocation will be described with reference to FIG. 8.

[0042] In S481, the normal path defragmentation unit 114 extracts the currently used wavelength and bandwidth of the normal path from the path information DB 121, in S482 creates a list in which the paths are sorted in descending order of the used wavelength and bandwidth, and in S483 extracts paths from the top of the list.

[0043] In S484, the normal path defragmentation unit 114 selects candidate wavelengths for reallocation in ascending order of wavelength number, extracts unused links for the candidate wavelengths for reallocation in S485, and determines whether or not it is possible to change the route of the path using the unused link in S486. If Yes, proceed to S487, and if No, return to S484.

[0044] In S487, the normal path defragmentation unit 114 changes the route and reallocates the path to the reallocated wavelength, and in S488, if there is no reallocatable path, the process ends, and if there is a reallocatable path, the process returns to S483.

[0045] (Regarding the priority of S30 and S40) In any of the above S30 to S40, the priority of reallocation is determined in descending order of the length of the route that the wavelength path takes from the start node to the end node (length of the wavelength path) and the bandwidth used by the path. Specifically, it can be determined as in a or b below.

[0046] a. After determining the priority in descending order of the length of the route that the wavelength path takes from the start node to the end node (length of the wavelength path), if the wavelength paths have the same length, the priority is determined in descending order of the bandwidth used by the path.

[0047] b. After determining the priority in descending order of the bandwidth used by the path, if the bandwidths are the same, the priority is determined in descending order of the length of the wavelength path.

[0048] The method of determining the priority is not limited to the above, and the priority of the wavelength paths may be determined randomly, for example.

[0049] However, the method of determining the priority is not limited to the above method, and the priority may be determined by a method other than the above method.

[0050] (Example) An embodiment of wavelength defragmentation processing by the wavelength defragmentation device 100 will be described below. Fig. 9 shows the overall configuration of an optical transmission network in this embodiment. As shown in Fig. 9, the optical network in this embodiment has a configuration in which nodes A to I are connected by links as shown in the figure. In this embodiment, wavelength allocation until wavelength defragmentation is performed is performed using the FF method. The FF method is a technique in which allocation is performed in ascending order of wavelength numbers.

[0051] Fig. 10 shows the wavelength allocation image of the optical transmission network. In Fig. 10, the same shading indicates the same path. For example, the path of G-H-I uses the wavelength with wavelength number 1.

[0052] Fig. 11 shows an example of the wavelength path information stored in the path information DB 121. Note that Fig. 11 is an example, and the items and storage formats are not limited to this. In the example of Fig. 11, the path ID, allocation status, service attribute, bandwidth, used wavelength number, start node, end node, and passing link are stored.

[0053] Fig. 12 shows an example of the information stored in the wavelength allocation management DB 122. As shown in Fig. 12, in the wavelength allocation management DB 122, for each wavelength number, information indicating whether the wavelength of that wavelength number is allocated to the link (1: allocated, 0: not allocated) is stored as the wavelength allocation status of each link constituting the optical transmission network. Note that the items and storage formats are not limited to this.

[0054] As described above, when the decrease in the wavelength utilization efficiency of the entire optical transmission network is detected by some means, the wavelength allocation management DB 122 and the path information DB 121 are set, and then wavelength defragmentation is executed. In wavelength defragmentation, as shown in Fig. 3, the low-latency path and the normal path are cancelled (S10), the wavelength reallocation of the high-reliability path is executed (S20), the wavelength reallocation of the low-latency path is executed (S30), and the wavelength reallocation of the normal path is executed (S40). Hereinafter, specific examples of S20 to S40 will be described.

[0055] <Specific Example of S20> First, a specific example of S20 (wavelength reallocation of the high-reliability path) under the wavelength utilization situation shown in Fig. 13 will be described. The path information DB 121 at this time is shown in Fig. 14. For example, from Fig. 13 and Fig. 14, it can be seen that the allocated path of path ID 1 is the path of the B-A-D route using the wavelength with wavelength number 1, and the service attribute is "high reliability".

[0056] The procedure described below is a more specific explanation of the procedure in the flowchart shown in Fig. 5. In the explanation of the following procedure, the step numbers in the flowchart shown in Fig. 5 are written as appropriate.

[0057] The highly reliable path defragmentation unit 112 extracts paths with a highly reliable attribute from the path information DB 121 shown in FIG. 14 (S21), and creates a list in which the paths are sorted in ascending order of wavelength usage numbers based on the currently used wavelength numbers (S22).

[0058] In a specific example, a wavelength path with a path ID of 1 (hereinafter referred to as path 1) and path 3 are stored in order from the top of the list.

[0059] The highly reliable path defragmentation unit 112 then searches for wavelengths that are candidates for reassignment of wavelength paths, starting from the top of the list (S23, S24, S25). In a specific example, first, a search is made for wavelengths that are candidates for reassignment of path 1, which is stored at the top of the list.

[0060] Here, since path 1 is already using the smallest wavelength number, no search is performed for wavelengths that are candidates for reallocation.

[0061] Next, the highly reliable path defragmentation unit 112 searches for a wavelength that is a candidate for reassignment for the wavelength path stored second in the list. In a specific example, the highly reliable path defragmentation unit 112 searches for a wavelength that is a candidate for reassignment for path 3. Since the highly reliable path accommodates a highly reliable service that does not tolerate a momentary interruption of the path, the highly reliable path defragmentation unit 112 performs defragmentation using a push-pull technique that enables uninterrupted defragmentation (Reference 1: F. Cugini, F. Paolucci, G. Meloni, G. Berrettini, M. Secondini, F. Fresi, N. Sambo, L.Poti, and P. Castoldi, ``Push-Pull Defragmentation Without Traffic Disruption in Flexible Grid Optical Network,'' IEEE J. Light. Netw., vol. 31, no. 1, Jan. 2013.).

[0062] To perform defragmentation using Push-Pull, all wavelengths from the currently used wavelength to the reassigned wavelength must be consecutively unused. Therefore, the wavelength assignment management DB 122 is referenced starting from the wavelength with the smallest wavelength number to check whether there are consecutive unused wavelengths up to the currently used wavelength, and the wavelength with the smallest wavelength number that can secure consecutive unused wavelengths is selected as the reassigned wavelength.

[0063] In the specific example, for path 3, the currently used wavelength is 3, and wavelengths 1 and 2 are consecutive vacant wavelengths, so wavelength 1 is selected as the reallocation destination wavelength for path 3.

[0064] As a result of the above, since the reallocation destination wavelength has been selected, the high-reliability path defragmentation unit 122 reallocates the wavelength path to the reallocation destination wavelength (S26). At this time, the high-reliability path defragmentation unit 122 changes the wavelength number used for the path to be reallocated in the path information DB 121. In addition, the wavelength allocation status in the wavelength allocation management DB 122 is also changed.

[0065] In a specific example, since wavelength 1 is selected as the reallocation destination wavelength of path 3 with a bandwidth of 1, the path accommodated in wavelength 3 is cancelled, and a new path is created to wavelength 1.

[0066] The above operations are similarly executed for all paths in the list (S27).

[0067] <Specific Example of S30> Next, a specific example of S30 (wavelength reallocation of low-latency paths) under the wavelength usage situation shown in FIG. 15 will be described. The path information DB121 at this time is shown in FIG. 16.

[0068] The procedure described below specifically describes the procedure of the flowchart shown in FIG. 6. In the description of the following procedure, the step numbers in the flowchart shown in FIG. 6 will be appropriately described.

[0069] The low-latency path deflagging unit 112 extracts paths with the attribute of low latency from the path information DB121 shown in FIG. 16 (S31), and creates a list in which the paths are sorted in descending order of bandwidth and path length (S32). In a specific example, path 2 and path 5 are stored in order from the top of the list.

[0070] Next, the low-latency path deflagging unit 112 searches for the wavelengths of the reallocation destination candidates of the wavelength paths in order from the top of the list (S33, S34, S35).

[0071] In a specific example, first, the wavelength of the reallocation destination candidate for path 2 stored at the top of the list is searched. At this time, since the low-latency path accommodates services for which the delay should be minimized as much as possible, the path needs to pass through the shortest path. Therefore, the path is accommodated in the same path as the path stored in the path information DB121.

[0072] At this time, the low-latency path defragmentation unit 112 refers to the wavelength allocation management DB 122 and the path information DB 121, and checks in order from the wavelength with the smallest wavelength number whether there is an available wavelength in the path described in the path information DB 121, and selects the available wavelength with the smallest wavelength number as the wavelength to be reallocated. In a specific example, for path 2 with a bandwidth of 1, since links CF and FI can be used with wavelength 2, wavelength 2 is selected as the wavelength to be reallocated for path 2.

[0073] As a result, since the wavelength to be reallocated is selected, the low-latency path defragmentation unit 112 reallocates the wavelength path to the wavelength to be reallocated (S36).

[0074] At this time, the low-latency path defragmentation unit 112 changes the used wavelength number and allocation status of the path to be reallocated in the path information DB 121. Also, changes are made to the wavelength allocation status in the wavelength allocation management DB 122. In a specific example, since wavelength 2 is selected as the wavelength to be reallocated for path 2, a new path is created to wavelength 2.

[0075] The above operations are similarly executed for all paths in the list (S37).

[0076] <Specific Example of S40> Next, a specific example of S40 (wavelength reallocation of normal paths) under the wavelength usage situation shown in FIG. 17 will be described. The path information DB 121 at this time is shown in FIG. 18.

[0077] The procedures described below more specifically explain the procedures of S41 to S47 in the flowchart shown in FIG. 7. In the description of the following procedures, the step numbers in the flowchart shown in FIG. 7 will be appropriately described.

[0078] The normal path defragmentation unit 114 extracts paths with normal attributes from the path information DB 121 shown in FIG. 18 and creates a list in which the paths are sorted in descending order of bandwidth and path length (S41, S42). In a specific example, path 6 and path 4 are stored in order from the top of the list.

[0079] Next, the normal path defragmentation unit 114 searches for wavelengths that are candidates for reassignment of wavelength paths, starting from the top of the list (S43, S44, S45). In a specific example, first, a search is made for wavelengths that are candidates for reassignment of path 6, which is stored at the top of the list.

[0080] Since normal paths accommodate services with few constraints on delay and reliability, it is possible to change the path route in order to improve the wavelength accommodation rate. Therefore, first, the path is accommodated on the same route as that stored in the path information DB 121 (flow in FIG. 7), and then the route is changed (flow in FIG. 8). First, the process of accommodating a path on the same route as that stored in the path information DB 121 will be described.

[0081] The normal path defragmentation unit 114 refers to the wavelength allocation management DB 122 and the path information DB 121, and checks whether any wavelengths are available on the route described in the path information DB 121, starting from the wavelength with the smallest wavelength number, and selects the available wavelength with the smallest wavelength number as the wavelength to be reassigned.

[0082] In the specific example, for path 6 with bandwidth 2, link AB, link BE, and link EH can be used for wavelength 2 and wavelength 3, so wavelengths 2 and 3 are selected as the reallocation wavelengths for path 6. As a result, since the reallocation wavelengths have been selected, the normal path defragmentation unit 114 reallocates the wavelength paths to the reallocation wavelengths (S46).

[0083] At this time, the normal path defragmentation unit 114 changes the wavelength numbers in use and the allocation status of the paths to be reallocated in the path information DB 121. It also changes the wavelength allocation status in the wavelength allocation management DB 122. In this specific example, since wavelengths 2 and 3 are selected as the reallocated wavelengths for path 6, new paths are created for wavelengths 2 and 3.

[0084] The normal path defragmentation unit 114 executes the above operation in the same manner for all paths in the list (S47).

[0085] The states of Figs. 17 and 18 after the above processing is applied are shown in Figs. 19 and 20, respectively.

[0086] <Specific Example of S48> Next, a specific example of S48 (path route change and reassignment) under the wavelength usage situation shown in FIG. 19 will be described. The path information DB121 at this time is as shown in FIG. 20.

[0087] The procedures described below explain the procedures of S481 to S488 in the flowchart shown in FIG. 8 in more detail. In the description of the following procedures, the step numbers in the flowchart shown in FIG. 8 will be described as appropriate.

[0088] The normal path defragmentation unit 114 extracts paths with normal attributes from the path information DB121 in FIG. 18 and creates a list in which the paths are sorted in descending order of the current used wavelength number and bandwidth (S481, S482). In a specific example, path 4 and path 6 are stored in order from the top of the list.

[0089] Next, the normal path defragmentation unit 114 searches for the wavelength and route of the candidate for wavelength path reassignment in order from the top of the list (S483 to S486). In a specific example, first, the wavelength and route of the candidate for reassignment are searched for path 4 stored at the top of the list.

[0090] At this time, the wavelength of the candidate for reassignment is selected in ascending order of the wavelength number (S484), and unused links with the wavelength of the candidate for reassignment are extracted from the wavelength assignment management DB122 (S485). Furthermore, if it is possible to construct a path via only the extracted unused links, the shortest path and wavelength among the constructed paths are selected as the new path and the wavelength of the candidate for reassignment (S486).

[0091] In a specific example, for path 4 with a bandwidth of 1, since a path passing through link GH, link DG, link DE, and link EF is available at wavelength 2, wavelength 2 is selected as the wavelength of the candidate for reassignment of path 4, and the path is changed to link GH, link DG, link DE, and link EF.

[0092] As a result, the reallocation destination wavelength and route have been selected, and the wavelength path is reallocated to the reallocation destination wavelength and the changed route (S487). At this time, the wavelength number in use and the transit link of the path to be reallocated in the path information DB 121 are changed. The wavelength allocation status in the wavelength allocation management DB 122 is also changed.

[0093] In this specific example, wavelength 2 is selected as the reallocation destination wavelength for path 4, and the route of links GH, DG, DE, and EF is selected, so a new path to wavelength 2 is created.

[0094] The normal path defragmentation unit 114 repeats the above operations until it becomes impossible to change the wavelengths used for all paths in the list (S488).

[0095] (Hardware configuration example) The wavelength defragmentation device 100 is realized as a device configured by, for example, causing a computer to execute a program. This computer may be a physical computer or a virtual machine.

[0096] That is, the device can be realized by executing a program corresponding to the processing performed by the device, using hardware resources such as a CPU and memory built into a computer. The program can be recorded on a computer-readable recording medium (such as a portable memory) and stored or distributed. The program can also be provided via a network such as the Internet or email.

[0097] Fig. 21 is a diagram showing an example of the hardware configuration of the computer. The computer in Fig. 21 has a drive device 1000, an auxiliary storage device 1002, a memory device 1003, a CPU 1004, an interface device 1005, a display device 1006, an input device 1007, an output device 1008, etc., which are all connected to each other via a bus BS.

[0098] The program for realizing the processing on the computer is provided by a recording medium 1001 such as a CD-ROM or a memory card. When the recording medium 1001 storing the program is set in the drive device 1000, the program is installed from the recording medium 1001 to the auxiliary storage device 1002 via the drive device 1000. However, the program does not necessarily have to be installed from the recording medium 1001, but may be downloaded from another computer via a network. The auxiliary storage device 1002 stores the installed program as well as necessary files, data, etc.

[0099] The memory device 1003 reads out and stores the program from the auxiliary storage device 1002 when an instruction to start the program is received. The CPU 1004 realizes the functions related to the device in accordance with the program stored in the memory device 1003. The interface device 1005 is used as an interface for connecting to a network. The display device 1006 displays a GUI (Graphical User Interface) or the like according to a program. The input device 1007 is composed of a keyboard and mouse, buttons, a touch panel, or the like, and is used to input various operation instructions. The output device 1008 outputs the results of calculations.

[0100] (Effects of the embodiment) As described above, in this embodiment, when optical paths are reallocated by wavelength defragmentation, operations are performed according to the attributes of the optical paths, making it possible to defragment wavelengths in accordance with the required quality of each optical path, enabling more flexible wavelength utilization.

[0101] Furthermore, it becomes possible to apply uninterrupted defragmentation to highly reliable paths that cannot tolerate interruptions in service, thereby making it possible to improve wavelength utilization efficiency.

[0102] (Summary of the embodiment) This specification discloses at least the wavelength defragmentation device, the wavelength defragmentation method, and the program described in the following items. (Section 1) A wavelength defragmentation device that performs wavelength reassignment for a path in an optical transmission network, comprising: A storage unit for storing a path information DB and a wavelength allocation management DB; a wavelength defragmentation function unit that refers to a path attribute from the path information DB and performs wavelength reallocation of a path having the attribute by an operation according to the attribute; A wavelength defragmentation device comprising: (Section 2) In the wavelength reassignment for the highly reliable path, the wavelength defragmentation functional unit checks whether or not the wavelengths are continuously available up to the currently used wavelength by referring to the wavelength assignment management DB in ascending order of wavelength number, and selects the wavelength with the smallest wavelength number for which continuous available wavelengths can be secured as the reassigned wavelength. 2. A wavelength defragmentation device as described in item 1. (Section 3) In wavelength reallocation for a low-latency path, the wavelength defragmentation function unit refers to the wavelength allocation management DB and the path information DB, checks whether wavelengths are available on the route of the low-latency path described in the path information DB, in ascending order of wavelength number, and selects the available wavelength with the smallest wavelength number as the wavelength to be reallocated. 3. A wavelength defragmentation device according to claim 1 or 2. (Section 4) In wavelength reallocation for a normal path, the wavelength defragmentation function unit refers to the wavelength allocation management DB and the path information DB, checks whether a wavelength is available on the route of the normal path described in the path information DB, in ascending order of wavelength number, selects an available wavelength having the smallest wavelength number as a reallocated wavelength, accommodates the normal path in the reallocated wavelength, and then changes the route of the normal path. 4. A wavelength defragmentation device according to claim 1. (Section 5) The wavelength defragmentation function unit determines the priority of wavelength reassignment in descending order of the length of the path that the path takes from the start node to the end node, or in descending order of the bandwidth used by the path. 5. A wavelength defragmentation device according to claim 3 or 4. (Section 6) A wavelength defragmentation method using a wavelength defragmentation device that includes a storage unit for storing a path information DB and a wavelength assignment management DB and executes wavelength reallocation for paths in an optical transmission network, comprising: The path attributes are referred to from the path information DB, and wavelength reallocation of the path having the attribute is performed by an operation according to the attribute. Wavelength defragmentation method. (Section 7) A program for causing a computer to function as each unit in a wavelength defragmentation device according to any one of claims 1 to 5.

[0103] Although the present embodiment has been described above, the present invention is not limited to such a specific embodiment, and various modifications and variations are possible within the scope of the gist of the present invention described in the claims. [Explanation of symbols]

[0104] 100 Wavelength Defragmenter 110 Wavelength defragmentation function unit 111 Wavelength cancellation section 112 Highly reliable path defragmentation unit 113 Low Latency Path Defragmentation 114 Normal Path Defragmentation Section 120 Storage section 121 Path Information DB 122 Wavelength Allocation Management DB 130 Input / Output Function Unit 131 Input section 132 Output section 200 Optical Transport Network 1000 Drive Device 1001 Recording media 1002 Auxiliary storage 1003 Memory device 1004 CPU 1005 Interface device 1006 Display device 1007 Input Device

Claims

1. A wavelength defragmentation device that performs wavelength reassignment for a path in an optical transmission network, comprising: a storage unit for storing a path information DB and a wavelength allocation management DB; a wavelength defragmentation function unit that refers to an attribute of a path from the path information DB and performs wavelength reallocation of a path having the attribute by an operation according to the attribute, the wavelength defragmentation functional unit, in wavelength reallocation to a highly reliable path, refers to the wavelength allocation management DB in ascending order of wavelength number to check whether wavelengths are continuously available up to the currently used wavelength, and selects the wavelength with the smallest wavelength number for which continuous available wavelengths can be secured as a reallocated wavelength; In reassigning wavelengths to a low-latency path, the wavelength defragmentation function unit refers to the wavelength assignment management DB and the path information DB, checks whether wavelengths are available on the route of the low-latency path described in the path information DB, in ascending order of wavelength number, and selects the available wavelength with the smallest wavelength number as the reassigned wavelength. Wavelength defragmenter.

2. A wavelength defragmentation device that performs wavelength reallocation for paths in an optical transmission network, comprising: a storage unit for storing a path information DB and a wavelength allocation management DB; a wavelength defragmentation function unit that refers to an attribute of a path from the path information DB and performs wavelength reallocation of a path having the attribute by an operation according to the attribute, In wavelength reallocation for a normal path, the wavelength defragmentation function unit refers to the wavelength allocation management DB and the path information DB, checks whether a wavelength is available on the route of the normal path described in the path information DB, in ascending order of wavelength number, selects an available wavelength having the smallest wavelength number as a reallocated wavelength, accommodates the normal path in the reallocated wavelength, and then changes the route of the normal path. Wavelength defragmenter.

3. The wavelength defragmentation function unit determines the priority of wavelength reassignment in descending order of the length of the path that the path takes from the start node to the end node, or in descending order of the bandwidth used by the path.

3. A wavelength defragmentation device according to claim 1 or 2.

4. A wavelength defragmentation method using a wavelength defragmentation device that includes a storage unit for storing a path information DB and a wavelength assignment management DB and executes wavelength reallocation for paths in an optical transmission network, comprising: a wavelength defragmentation method for referring to an attribute of a path from the path information DB and performing wavelength reallocation of a path having the attribute by an operation according to the attribute, In the wavelength defragmentation device, in the wavelength reassignment to the highly reliable path, the wavelength defragmentation device refers to the wavelength assignment management DB in ascending order of wavelength number to check whether wavelengths are continuously available up to the currently used wavelength, and selects the wavelength with the smallest wavelength number for which continuous available wavelengths can be secured as the reassigned wavelength; In reassigning wavelengths to a low-latency path, the wavelength defragmentation device refers to the wavelength assignment management DB and the path information DB, checks whether wavelengths are available on the route of the low-latency path described in the path information DB, in ascending order of wavelength number, and selects the available wavelength with the smallest wavelength number as the reassigned wavelength. Wavelength defragmentation method.

5. A program for causing a computer to function as each unit in the wavelength defragmentation device according to any one of claims 1 to 3.

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