Network designing device

Abstract

This network designing device comprises a calculation part. On the basis of information on nodes and links constituting a network for performing wavelength multiplex communication, the number of wavelengths transmittable through a transmission path for transmitting a signal of a link, a plurality of types of paths represented by a link from a start point node to an end point node, and a set of node pairs of a start point node and an end point node for performing communication, the calculation part calculates a link for use in transmitting a signal of the set of node pairs so as to reduce the number of transmission paths that are used, under conditions in which the nodes perform signal switching for transmission path units, a spare path and a main path for transmitting signals of the same node pair do not include the same link, and a plurality of spare paths in which the corresponding main paths do not share a link can use the same resource.

Description

Network design equipment

[0001] The present invention relates to a network design device.

[0002] In recent years, spatial multiplexing and wavelength division multiplexing (WDM) have been considered to improve bandwidth utilization efficiency in networks. Meanwhile, shared protection is a highly reliable route design method for conventional WDM networks (see, for example, Non-Patent Documents 1 and 2). Shared protection assumes a single failure and optimizes the main route and backup route using shared backup path protection (SBPP). As shown in Figure 10, SBPP is a route design method that allows backup routes to share link resources (wavelengths) when corresponding main routes are edge-disjoint. While switching at nodes is performed wavelength-by-wavelength, in ultraviolet WDM, the guard band between adjacent channels is set narrow, which often causes bandwidth narrowing in filters within WSSs (Wavelength Selective Switches), resulting in signal degradation, as shown in Figure 11. Furthermore, SBPP does not formulate spatial multiplexing networks.

[0003] Therefore, there is a network resource design (fiber planning) optimization method that takes bandwidth narrowing into account in an ultraviolet WDM network (see, for example, Non-Patent Document 3). As shown in Figure 12, this is a network (subnetwork) design optimization method that suppresses bandwidth narrowing by designing a subnetwork that performs switching on a fiber-by-fiber basis using FXC (fiber cross-connect) and routing paths there by adding / dropping on a wavelength-by-wavelength basis. With this resource design method, the number of fibers used in some links may be large, which can increase the risk of link failure. Furthermore, wavelength continuity is not taken into account in the formulation.

[0004] S. Ramamurthy, Laxman Sahasrabuddhe, and Biswanath Mukherjee, “Survivable WDM Mesh Networks”, Journal of lightwave technology, vol. 21, no. 4, 2003, p.870-883Jane M. Simmons, “Chapter 7 Optical Protection”, Optical Network Design and Planning, Springer Link, 2014, p.277-284Ryuta Shiraki, Yojiro Mori, Hiroshi Hasegawa, Ken-Ichi Sato, and Paolo Monti, “Design and control of highly spectrally efficient photonic networks enabled by fiber-granular routing on overlaid ring-shaped topologies”, Journal of Optical Communications and Networking, Vol. 13, No. 11, 2021, p.233-243

[0005] As mentioned above, network design optimization methods have been proposed to reduce bandwidth narrowing, but they have the following issues. First, they do not take reliability into consideration, and the fiber used may be concentrated in certain links, resulting in a high risk of link failure. Because the node configuration does not require wavelength switching, it is desirable to consider wavelength continuity when optimizing the network design. Furthermore, while highly reliable route design methods such as shared protection exist, none have been considered that take into account both spatial multiplexing and bandwidth narrowing. Thus, it has been difficult to minimize bandwidth narrowing while simultaneously optimizing route and network design in an ultraviolet WDM network, taking reliability into consideration.

[0006] In view of the above circumstances, an object of the present invention is to provide a network design device that can perform highly reliable network design while suppressing bandwidth narrowing in a network that transmits wavelength multiplexed signals.

[0007] A network design device according to one embodiment of the present invention comprises a calculation unit that calculates the links to be used to transmit signals of the set of node pairs based on information on the nodes and links that constitute a network performing wavelength multiplexing communication, the number of wavelengths that can be transmitted by the transmission paths that transmit signals of the links, multiple types of paths represented by the links from the starting node to the ending node, and a set of node pairs of the starting node and the ending node that communicate, so as to reduce the number of transmission paths to be used under the conditions that the nodes perform signal switching on a transmission path basis, the main route and backup route that transmit signals of the same node pair do not include the same link, and multiple backup routes where corresponding main routes are edge elements can use the same link and wavelength resources.

[0008] The present invention makes it possible to design a highly reliable network that suppresses bandwidth narrowing in a network that transmits wavelength-multiplexed signals.

[0009] 1 is a configuration diagram of a network design device according to an embodiment of the present invention. FIG. 2 is a diagram showing an example of a node configuration according to an embodiment. FIG. 3 is a diagram for explaining resources according to an embodiment. FIG. 4 is a flow diagram showing processing of a network design device according to an embodiment. FIG. 5 is a diagram showing a specific example of optimization according to an embodiment. FIG. 6 is a diagram showing a specific example of optimization according to an embodiment. FIG. 7 is a diagram showing a graph of a physical topology used in an experiment of a network design device according to an embodiment. FIG. 8 is a diagram showing experimental results of a network design device according to an embodiment. FIG. 9 is a diagram showing an example of a hardware configuration of a network design device according to an embodiment. FIG. 10 is a diagram showing a network design method according to a conventional technology. FIG. 11 is a diagram showing bandwidth narrowing that occurs in a network design method according to a conventional technology. FIG. 12 is a diagram showing a subnetwork used in a network design method according to a conventional technology.

[0010] An embodiment of the present invention will be described in detail below with reference to the drawings. This embodiment relates to an optimization technology for designing communication paths and spatially multiplexed optical networks while suppressing bandwidth narrowing in an ultraviolet WDM network and taking reliability into consideration. In this embodiment, similar to the technology in Non-Patent Document 1, a filterless drop is performed using a splitter, so bandwidth narrowing occurs only when a path to an adjacent wavelength is added. Furthermore, by providing backup paths, a single link failure does not affect communication. In addition, by taking wavelength allocation into consideration, more accurate network design is achieved. This embodiment employs shared backup path protection (SBPP), which provides higher resource utilization efficiency than dedicated backup path protection (DBPP), a route design method in which backup paths do not allow resource sharing between each other and each backup path occupies bandwidth for each request. Furthermore, when considering only already installed fiber, it is possible to add a constraint on the number of fibers available in each link.

[0011] Fig. 1 is a functional block diagram showing the configuration of a network design device 1 according to an embodiment of the present invention. Fig. 1 shows only functional blocks related to this embodiment. The network design device 1 can be realized, for example, by a computer device.

[0012] The network design device 1 is connected to a network (NW) management device 2. The NW management device 2 manages a network 3. The network 3 performs wavelength multiplexing communication. Each circle in the network 3 represents a node, and links, which are logical connections, are established between the nodes. The numbers inside the nodes represent node numbers. In this embodiment, the node numbers are used as node identifiers. The nodes are, for example, FXCs (Fiber cross-connects). The i-th node (i = 1, 2, ...) is referred to as node i. The NW management device 2 sets up a subnetwork for each node in the network 3 so that optical signal switching is performed on a fiber-by-fiber basis according to the information received from the network design device 1.

[0013] A subnetwork is a sub-network of network 3. A subnetwork is a one-way, unbranched, directed simple path or a directed simple closed path, with at most one fiber per edge. One-way traffic refers to the unidirectional transmission of optical signals on each link included in the subnetwork. Branching refers to optical signals input from two or more fibers at a node being output to one fiber, or optical signals input from one fiber at a node being output to two or more fibers. Therefore, the shape of a subnetwork is ring-shaped or linear. The main and backup routes between nodes use at least a portion of different subnetworks to form edge elements (do not use the same links). By using subnetworks, routing is performed on a fiber-by-fiber basis, eliminating the need for wavelength-by-wavelength routing at nodes, thereby reducing bandwidth narrowing.

[0014] The network design device 1 includes a database 11 and a route calculation unit 12. The database 11 is a storage unit that stores various information. The database 11 records information on the physical topology G(V, E) (V: node set, E: edge set) of the network 3, the number of wavelengths per fiber W, and K-shortest paths (KSP), a set of paths connecting each node pair (s, d). Edges correspond to links. A path connecting a node pair (s, d) is represented by the set of edges that run from node s to node d. Note that if the physical topology becomes disconnected when a link (edge) included in a path is removed (i.e., no other available path from node s to node d exists), there is no edge-disjoint path that can serve as a backup route, and therefore such a path is not included in the KSP.

[0015] The path calculation unit 12 includes an input unit 13, an optimization calculation unit 14, and an output unit 15. The input unit 13 reads information on the physical topology G, the number of wavelengths per fiber W, and the set of paths KSP connecting each node pair from the database 11, and inputs the read information to the optimization calculation unit 14. Furthermore, the input unit 13 inputs information on a demand forecast R received from the NW management device 2 to the optimization calculation unit 14. The demand forecast R is a set of requests r. The request r represents a pair of a node s that adds an optical signal and a node d that drops the optical signal, i.e., a node pair that communicates. The input unit 13 may input information received from another computer device connected via the network to the optimization calculation unit 14, or may input information read from a computer-readable recording medium to the optimization calculation unit 14. The input unit 13 may also acquire information input by a user via a keyboard, a mouse, a touch panel, a button, a key, or the like.

[0016] The optimization calculation unit 14 calculates a main route t for a request r (node ​​pair) indicated by the demand forecast R based on the demand forecast R and the physical topology G read from the database 11, the number of wavelengths W per fiber, and the set KSP of paths connecting each node pair. ｒ ｎ，ｗ，ｋ and preliminary routes ＾ t ｒ n, w, k_p, k_b, and a subnetwork f including the main and spare routes ｎ，ｅ Calculate the main path t ｒ ｎ，ｗ，ｋ and preliminary routes ＾ t ｒ n, w, k_p, and k_b are binary variables that take the value 1 when the nth subnetwork and the kth path of request r in KSP are assigned to the main and backup routes of request r, respectively. ｎ，ｅ is a binary variable that takes the value 1 if the nth subnetwork contains edge e.

[0017] The optimization calculation unit 14 includes a main path output unit 141, a backup path output unit 142, and a resource information output unit 143. The main path output unit 141 outputs the calculated main path t ｒ ｎ，ｗ，ｋThe preparatory route output unit 142 outputs the calculated preparatory route. ＾ t ｒ The resource information output unit 143 outputs information on n, w, k_p, and k_b. ｎ，ｅ Outputs information about.

[0018] The output unit 15 outputs the main path t ｒ ｎ，ｗ，ｋ Information, preliminary route ＾ t ｒ n, w, k_p, k_b information and subnetwork f ｎ，ｅ The output unit 15 writes the information of the sub-network f ｎ，ｅ The NW management device 2 outputs the received information of the subnetwork f ｎ，ｅ By instructing each node of the network 3 to switch optical signals on a transmission path basis in accordance with the information, the main path and backup path for each request r included in the demand forecast are opened.

[0019] 2 is a diagram showing an example of the configuration of a node in network 3. FXC 4 is connected to fibers 51-1 to 51-J (J is an integer equal to or greater than 1) via splitters 6-1 to 6-J, respectively. FXC 4 is also connected to fibers 52-1 to 52-M (M is an integer equal to or greater than 1) via WSSs (Wavelength Selective Switches) 7-1 to 7-M, respectively. Fibers 51-1 to 51-J and 52-1 to 52-M are transmission paths for transmitting optical signals.

[0020] Splitter 6-j (j is an integer between 1 and J) inputs the optical signal transmitted through fiber 51-j to FXC4 or drops it, in accordance with the setting by the NW management device 2. FXC4 outputs the optical signal input from splitter 6-j to WSS 7-m connected to fiber 52-m (m is an integer between 1 and M), in accordance with the setting by the NW management device 2. WSS 7-m adds an optical signal with a different wavelength from the optical signal output by FXC4 to the optical signal output by FXC4, and outputs the added signal to fiber 52-m.

[0021] Next, UDWDM-SBPP (shared backup path protection in consideration of bandwidth narrowing in ultraviolet WDM), which is an optimization method performed by the path calculation unit 12, will be described.

[0022] <Given Information> The following (a1) to (a4) are given.

[0023]

[0024] The physical topology G is represented by a node set V and a set E of edges e. When an edge e is a link between node u and node v included in node set V, it is represented by a pair (u, v) of node u and node v. A set W of wavelengths is a set of wavelengths that can be transmitted in one fiber. A demand forecast R is a set of requests r that represent node pairs that communicate. Each request r is represented by a pair (s, d) of node s and node d included in node set V. Node s is the starting node that adds an optical signal, and node d is the ending node that drops an optical signal. KSP ｒ is the set of K-shortest paths connecting node pairs (s, d). Each path is a route represented by a set of consecutive edges (links) from node s to node d that constitutes request r.

[0025] <Constants> The following constants (b1) to (b4) are used.

[0026]

[0027] In the following, the subnetwork with identifier n included in the set N of subnetwork identifiers will be referred to as subnetwork n. Also, the wavelength with identifier w among the set W of identifiers of wavelengths that can be transmitted through the fiber will be referred to as wavelength w. The edge information L(r, k, e) along which each path passes is used as the KSP for request r. ｒ Path p, which is the kth path of ｒ ｋ If passes through edge e, it is 1, otherwise it is 0.

[0028] <Binary Variables> The following binary variables (c1) to (c5) are used.

[0029]

[0030] f ｎ，ｅ is 1 if the subnetwork n includes the edge e, and is 0 if it does not. ｎ，ｅ Subnetwork n is represented by edge e where t is 1. ｒ ｎ，ｗ，ｋ is the wavelength w and KSP in the subnetwork n on the main route of the request r. ｒ The kth path p ｒ ｋ When the byte is assigned, it is 1, otherwise it is 0. ＾ t ｒ n, w, k_p, k_b are the KSPs on the main path of request r. ｒ No.K ｐ th pass p ｒ ｋ＿ｐ is assigned to the backup route for request r, and wavelength w and KSP in subnetwork n are assigned to the backup route for request r. ｒ No.K ｂ th pass p ｒ ｋ＿ｂ If P is assigned, it is 1, otherwise it is 0. ｎ，ｗ，ｅ is 1 when wavelength w and edge e of subnetwork n are assigned to the main path, and 0 otherwise. ｎ，ｗ，ｅ is 1 when wavelength w and edge e of subnetwork n are assigned to the spare route, and is 0 otherwise.

[0031] <Objective function> The objective function f is a function that minimizes the number of fibers required to configure a subnetwork so as to satisfy the objective function of the following equation (1). ｎ，ｅ Ask for.

[0032]

[0033] If edge e of subnetwork n is used as a main path or a backup path, then f ｎ，ｅ On the other hand, if edge e of subnetwork n is not used in either the main route or the backup route, f ｎ，ｅ is 0. f with value 1 for some edge e ｎ，ｅ The number of fibers required for the link corresponding to the edge e is given by the number of fibers required for the link corresponding to the edge e.

[0034] <Constraint Conditions> The path calculation unit 12 calculates f that minimizes the objective function of Equation (1) under the following constraint conditions: ｎ，ｅ Ask for.

[0035] First, a subnetwork, wavelength, and route are assigned to the main route and backup route of each request according to the following equations (2) and (3).

[0036]

[0037] According to equation (2), the main route of each request r is assigned a wavelength w and a KSP in a certain subnetwork n. ｒ A path p ｒ ｋ This is a constraint that only one wavelength and path of a certain subnetwork must be assigned to the main route of request r, and not more than one. ｒ ｋ The constraint is that the

[0038] Furthermore, the spare route of each request r is assigned by equation (3). That is, k is assigned to the main route of request r. ｐ th pass p ｒ ｋｐ is assigned, the backup route for request r is assigned a wavelength w in a certain subnetwork n and KSP ｒ Aru K ｂ th pass p ｒ ｋｂ This is a constraint that only one wavelength w and path of a certain subnetwork n must be assigned to the backup route of request r, and two or more must not be assigned. ｒ ｋｂ The constraint is that the

[0039] Since the main route and backup route of each request are edge disjoint, the following equations (4) and (5) are used as constraints.

[0040]

[0041] When neither a main route nor a backup route is assigned to side e, the left sides of equations (4) and (5) are 0, and when a main route or a backup route is assigned to side e, one of equations (4) and (5) is 0 and the other is 1. These satisfy the constraints. When a main route and a backup route are assigned to side e, either equation (4) or equation (5) is 2, and therefore the constraints are not satisfied.

[0042] Next, values ​​used for resource constraints are calculated. First, it is determined whether or not resources are allocated to the main route using equation (6).

[0043]

[0044] 3 is a diagram for explaining resources. As shown in the figure, a resource (n, w, e) is specified by a subnetwork n, a wavelength w, and an edge e. When a main route of any request r is assigned to the resource (n, w, e), P obtained in equation (6) is ｎ，ｗ，ｅ is 1, otherwise it is 0.

[0045] Next, it is determined whether each resource can be allocated to the backup path using equations (7) and (8).

[0046]

[0047] If resources (n, w, e) are allocated to the backup path of request r so as to satisfy the conditions of equations (7) and (8), then B ｎ，ｗ，ｅ is 1, otherwise it is 0. In equation (7), the constraint is that for each failure event, only one request r can be simultaneously diverted to resource (n, w, e). In equation (8), the constraint is that multiple requests r can be allocated to the backup path for resource (n, w, e).

[0048] Since the route assigned to each resource is either the main route or the backup route, the equation (9) is used as a constraint.

[0049]

[0050] When either the main route or the backup route is assigned to resource (n, w, e), the left side of equation (9) is 1, and when neither the main route nor the backup route is assigned to resource (n, w, e), the left side of equation (9) is 0. These satisfy the constraint. When both the main route and the backup route are assigned to resource (n, w, e), equation (9) becomes 2, which does not satisfy the constraint.

[0051] Furthermore, the following equation (10) is used as a constraint that the resources used in each edge e of the subnetwork n do not exceed the number of resources available in the fiber.

[0052]

[0053] Since the sub-network is one-way and has no branches, the following equations (11) and (12) are set as constraints.

[0054]

[0055] Equation (11) indicates a constraint that each edge between node u and node v in each subnetwork n must be one-way. Equation (12) indicates a constraint that each edge must not branch, by the sum of the number of links coming into a node v in each subnetwork n and the number of links going out from that node v being 2 or less.

[0056] There are two key points in formulating the optimization method described above. The first point is the formulation of shared protection. The technology of Non-Patent Document 1 does not provide a formulation that corresponds to spatial multiplexing. In this embodiment, the formulation is extended to the case of spatial multiplexing by using a subnetwork identifier. Furthermore, resource sharing of backup paths is formulated as a linear expression using two constraint equations for resource (n, w, e) expressed by equations (7) and (8). That is, equation (7) limits the number of requests that can be simultaneously detouring to resource (n, w, e) for each failure event to one. Furthermore, there may be multiple requests that can be assigned resource (n, w, e) to a backup path, and the number of requests is expressed as B in equation (8). ｎ，ｗ，ｅ is used to count.

[0057] The second point is the configuration of the sub-network. In this embodiment, the sub-network is configured so that the number of fibers used as a whole is as small as possible. Therefore, when a resource (n, w, e) is allocated to at least one wavelength w, the number of fibers f ｎ，ｅ Furthermore, the sum of the number of fibers used on each edge of all sub-networks is minimized by using equation (1). In addition, by configuring the sub-network without branching using equations (11) and (12), routing is performed only by fiber-by-fiber switching using FXC, thereby suppressing bandwidth narrowing.

[0058] Next, a description will be given of the processing of the network design device 1. FIG.

[0059] The input unit 13 of the network design device 1 receives the demand forecast R from the NW management device 2 and inputs it to the optimization calculation unit 14 (step S1). The input unit 13 receives from the database 11 the physical topology G of the network 3, the set of wavelengths W, and the set of paths KSP of each request r included in the demand forecast R. ｒ The optimization calculation unit 14 reads out the information on the demand forecast R input in step S1, and the physical topology G, wavelength set W, and KSP input in step S2. ｒ Using the information of f so as to satisfy the above equation (1), ｎ，ｅ is calculated in accordance with the conditions of equations (2) to (12) (step S3).

[0060] The main path output unit 141 of the optimization calculation unit 14 outputs the calculated f ｎ，ｅ When t is obtained ｒ ｎ，ｗ，ｋ The preliminary path output unit 142 outputs the calculated f ｎ，ｅ When ＾ t ｒ The resource information output unit 143 outputs n, w, k_p, and k_b. ｎ，ｅ The resource information output unit 143 outputs f ｎ，ｅ and outputs f with a value of 0. ｎ，ｅThe output unit 15 does not need to output t ｒ ｎ，ｗ，ｋ Information on the main route indicated by ＾ t ｒ Information on the preliminary route indicated by n, w, k_p, and k_b, and f ｎ，ｅ The information on the subnetwork indicated by the symbol .alpha. is written to the database 11. The output unit 15 also outputs the information on the subnetwork to the NW management device 2 (step S4).

[0061] The NW management device 2 instructs each node of the network 3 to perform switching in accordance with the information on the subnetwork received from the network design device 1. As a result, the main route and backup route for each request r included in the demand forecast R are opened.

[0062] 5 and 6 are diagrams illustrating specific examples of optimization. Demand forecast R includes requests r=(3,1), (7,6), (10,4), (9,7), and (1,8). As a result of calculations by the optimization calculation unit 14, subnetwork 4 shown in FIG. 5(a) is used for the main route, and subnetworks 6, 7, and 9 shown in FIG. 5(b) are used for the backup route. Subnetwork 4 consists of edges between nodes [(1,9), (8,7), (9,8), (10,1), (3,10), (4,3), (5,4), (6,5), and (7,6)]. Subnetwork 6 consists of edges between nodes [(8,9), (9,6), (6,7), and (7,8)]. Subnetwork 7 consists of edges between nodes [(2,1), (10,4), and (3,2)]. Subnetwork 9 consists of edges between nodes of edge [(0,8), (1,0)]. The number of fibers used in these subnetworks is 18.

[0063] w_subNW is the identifier of the subnetwork used by the main route, w_path_edges is the edge (link) used by the main route, b_subNW is the identifier of the subnetwork used by the backup route, and b_path_edges is the edge (link) used by the backup route. For example, the main route of request r=(3,1) uses the edge [(3,10), (10,1)] of subnetwork 4, and the backup route uses the edge [(3,2), (2,1)] of subnetwork 7. Also, the main route of request r=(7,6) uses the edge (7,6) of subnetwork 4, and the backup route uses the edge [(7,8), (8,9), (9,6)] of subnetwork 6.

[0064] Next, we will show the results of an experiment using the network design device 1. In the experiment, we will show the results of calculating network design using UDWDM-ILP (this embodiment) and DWDM-ILP (conventional method). DWDM-ILP is shared backup path protection in DWDM (dense WDM) that does not take bandwidth narrowing into consideration.

[0065] Figure 7 shows a graph of the physical topology used in the experiment. Simulations were performed using the topology model shown in Figure 7, with the number of wavelengths W = 3 for DWDM and W = 4 for UDWDM. The demand forecast R∋r = (s, d) was calculated by randomly selecting all node pairs (20 pairs in total) and calculating the required number of fibers.

[0066] Figure 8 shows the results of calculations using UDWDM-ILP (this embodiment) and DWDM-ILP. The results shown in the graph are the average of 10 trials. Figure 8 shows that the UDWDM-ILP of this embodiment can reduce the number of fibers required for network design by an average of about 11% compared to the conventional DWDM-ILP method. It was also confirmed that the effects of ultraviolet DWDM can be obtained when reliability (shared protection) is taken into consideration.

[0067] As described above, the network design device 1 includes the database 11 and the route calculation unit 12. The database 11 stores information on the physical topology G, the number of wavelengths per fiber W, and KSP. The database 11 also stores information on the fiber layout calculated by the route calculation unit 12. Upon receiving the demand forecast R, the route calculation unit 12 reads G, W, and KSP stored in the database 11 and calculates the main route and backup route for each node pair included in the demand forecast R so as to minimize the resources required for the forecasted demand, i.e., the number of fibers constituting the subnetwork. The route calculation unit 12 writes the calculated main route and backup route and information on the required resources to the database 11 and transmits the fiber layout information to the NW management device 2. Based on the received fiber layout information, the NW management device 2 changes the switching of the FXC 4 to configure a subnetwork corresponding to the demand forecast.

[0068] The route calculation unit 12 calculates the main route, backup route, and resources based on the integer linear programming problem described in the optimization method. The key features of the optimization method are as follows: First, routing over a subnetwork that switches on a fiber-by-fiber basis enables high bandwidth utilization efficiency of ultraviolet WDM while suppressing bandwidth narrowing. Second, designing both the main route and backup route and configuring a subnetwork to accommodate them makes it possible to eliminate the impact of single-link failures. Existing SBPP-based route design methods, such as those described in Non-Patent Document 1, do not take bandwidth narrowing into account, so a formulation that uses spatial multiplexing to configure a subnetwork, as in this embodiment, is required. Furthermore, existing subnetwork design methods, such as those described in Non-Patent Document 1, or their repeated application, are unable to design shared backup path protection routes, necessitating a new formulation like that described in this embodiment. Furthermore, the optimization method of this embodiment allocates wavelengths and considers wavelength continuity constraints, enabling more accurate optical network design than when wavelength allocation is not considered. Furthermore, when using only installed resources, it is also possible to add a constraint on the number of fibers available for each link.

[0069] 9 is a diagram illustrating an example of the hardware configuration of the network design device 1. The network design device 1 includes a processor 91, a storage unit 92, a communication interface 93, and a user interface 94.

[0070] The processor 91 is a central processing unit that performs calculations and control. The processor 91 is, for example, a CPU (central processing unit) or a GPU (graphics processing unit). The processor 91 reads and executes programs from a storage unit 92. The storage unit 92 further has a work area and the like for the processor 91 to execute various programs. The communication interface 93 is connected to other devices so as to be able to communicate with them. The user interface 94 is an input device such as a keyboard, a pointing device (mouse, tablet, etc.), a button, a touch panel, etc., and a display device such as a display. Human operations are input via the user interface 94.

[0071] At least some of the functions of the path calculation unit 12 of the network design device 1 are realized by the processor 91 reading and executing a program from the storage unit 92. The program of the network design device 1 may be recorded on a computer-readable recording medium. Examples of computer-readable recording media include portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, and storage devices such as hard disks built into computer systems. The program of the network design device 1 may be transmitted via a telecommunications line. At least some of the functions of the network design device 1 may be realized using hardware such as an application-specific integrated circuit (ASIC), a programmable logic device (PLD), or a field-programmable gate array (FPGA). The database 11 is realized using the storage unit 72.

[0072] Furthermore, the network design device 1 may not have the database 11 inside, but the database 11 may be provided in another device connected to the network design device 1 .

[0073] The network design device 1 may also be implemented by multiple computers connected to the network. In this case, it is possible to arbitrarily determine which of the multiple computers implements each functional unit of the network design device 1. For example, the database 11 and the path calculation unit 12 may each be implemented by a different computer. Furthermore, the same functional unit may be implemented by multiple computers. For example, the optimization calculation unit 14 may be implemented by multiple computers, and the processing of step S3 may be performed in parallel.

[0074] According to the above-described embodiment, the network design device includes a calculation unit. The calculation unit corresponds to, for example, the route calculation unit 12 in the embodiment. Based on information on the nodes and links constituting a network that performs wavelength multiplexing communication, the number of wavelengths that can be transmitted by the transmission paths that transmit signals of the links, multiple types of paths represented by links from start nodes to end nodes, and a set of node pairs each consisting of a start node and an end node that communicate, the calculation unit calculates links to be used to transmit signals of the set of node pairs so as to reduce the number of transmission paths to be used, under the conditions that the nodes perform signal switching on a transmission path basis, the main route and the backup route that transmit signals of the same node pair do not include the same link, and multiple backup routes that are edge elements of the corresponding main routes can use the same link and wavelength resources.

[0075] Information on the nodes and links that make up a network that performs wavelength multiplexing communication corresponds, for example, to information on the physical topology G in the embodiment. The number of wavelengths that can be transmitted through a transmission path that transmits link signals corresponds to the number of wavelengths W in the embodiment. Multiple types of paths represented by links from a start node to an end node correspond to KSP in the embodiment. A set of node pairs, each consisting of a start node and an end node that communicate, corresponds to a demand forecast R in the embodiment.

[0076] The calculation unit may calculate links to be used to transmit signals of a set of node pairs so that a path serving as a main route and a path serving as a backup route for the same node pair do not pass through the same links and so that the number of signals transmitted through links of a subnetwork including the paths does not exceed the number of wavelengths that can be transmitted. A subnetwork is a partial network that does not branch off from a network and transmits signals in one direction. Since a path serving as a main route and a path serving as a backup route for the same node pair do not pass through the same links, these paths are consequently routed in different subnetworks.

[0077] The calculator may calculate links to be used to transmit signals for a set of node pairs under the above conditions expressed by an integer linear programming problem.

[0078] The network design device of this embodiment can also be realized by a computer and a program, and the program can be recorded on a recording medium or provided via a network.

[0079] Although the embodiments of the present invention have been described in detail above with reference to the drawings, the specific configurations are not limited to these embodiments, and include designs within the scope of the present invention that do not deviate from the gist of the present invention.

[0080] REFERENCE SIGNS LIST 1 Network design device 2 Network management device 3 Network 4 FXC 6-1 to 6-J Splitter 7-1 to 7-M WSS 11 Database 12 Route calculation unit 13 Input unit 14 Optimization calculation unit 15 Output unit 51-1 to 51-J, 52-1 to 52-M Fiber 141 Main route output unit 142 Backup route output unit 143 Resource information output unit

Claims

1. A network design device comprising: a calculation unit that calculates the links to be used to transmit signals of a set of node pairs based on information on the nodes and links that constitute a network that performs wavelength multiplexing communications, the number of wavelengths that can be transmitted by the transmission paths that transmit signals of the links, multiple types of paths represented by the links from the starting node to the ending node, and a set of node pairs of the starting node and the ending node that communicate, so as to reduce the number of transmission paths to be used under the condition that the nodes perform signal switching on a transmission path basis, main paths and backup paths that transmit signals of the same node pair do not include the same link, and corresponding main paths do not share links and multiple backup paths can use the same link and wavelength resources.

2. The network design device of claim 1, wherein the calculation unit calculates the links to be used to transmit signals for the set of node pairs so that the path that is the main route and the path that is the backup route for the same node pair do not pass through the same link, and the number of signals transmitted through the links included in the subnetwork that includes the path does not exceed the number of wavelengths that can be transmitted through the transmission path, and the subnetwork is a partial network of the network that does not branch and transmits signals in one direction.

3. The network design device according to claim 1 or 2, wherein the calculation unit calculates the links to be used for transmitting signals of the set of node pairs under the conditions expressed by an integer linear programming problem.

Images