JP4024253B2 - Optimal optical path search method - Google Patents

Description

  The present invention relates to an optimum optical path search method.

  In recent years, packet-based data traffic has increased rapidly due to the spread of the Internet and the like. Correspondingly, high-speed and large-capacity optical networks using optical fibers and the like are being developed. In such an optical network, a wavelength division multiplexing (WDM) method has attracted attention. In the WDM method, transmission capacity can be increased without increasing the number of optical fibers by transmitting optical signals having different wavelengths in parallel on the optical fiber.

  As an apparatus used in the WDM method, an optical add / drop multiplexing (OADM) apparatus, an optical cross connect (OXC) apparatus, or the like is realized. The OADM device can set a plurality of optical paths by adding and dropping an optical signal having an arbitrary wavelength from an optical fiber. Further, the OXC apparatus can switch the input optical signal to an arbitrary optical path.

  In a device that combines the cross-connect function provided in the OXC device and the IP packet transfer function provided in the router, the optical signal cut-through in the device, that is, the device Passing through can be realized. By this optical signal cut-through, a desired optical path can be set between arbitrary nodes, and a network topology different from the physical configuration can be configured.

For example, Patent Document 1 describes an optical wavelength cut-through network and an optical cross-connect device that periodically switch paths using a cut-through technique.
JP 2002-374291 A

  However, the above-described conventional optical wavelength cut-through network reduces the processing load of the router included in the node by setting the optical path so as to cut through the node whose processing load has increased due to the concentration of traffic. It is aimed. Therefore, when an optical path is set so as to reduce the load on only a specific router as in the conventional example, the load on other routers may be affected. This is because the routing information in the IP layer is changed by setting a new cut-through path, and for example, the processing load at the nodes at both ends of the cut-through path may increase.

  For this reason, when setting a cut-through path, it is desired to realize an optical path setting method that reduces the processing load on the entire network in consideration of changes in the IP path topology. However, when considering a reduction in processing load on the entire network, the number of cut-through path setting patterns increases exponentially as the number of nodes and the number of usable wavelengths increase. For this reason, it is not realistic to find the best setting pattern by searching the optical path topology of all patterns.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to search for the best optical path topology at high speed without searching for the optical path topology of all patterns. It is to provide a method.

  In order to achieve the above-described object, an optimum optical path search method according to a first aspect of the present invention includes a plurality of nodes arranged in a mesh shape, and an optical fiber that transmits wavelength multiplexed optical signals by connecting adjacent nodes. In a meshed wavelength division multiplexing optical network including an optical path setting device connected to each of a plurality of nodes, a process for generating a new optical path topology is performed when a transition is made from an active optical path topology to an optimal optical path topology. And optical path topology comparison process.

  The new optical path topology generation process is a process of generating a new optical path topology, and further includes an initialization process, a node selection process, an optical path setting process, and a determination process. In the initialization process, a new optical path topology is initialized. In the node selection process, two nodes are selected using random numbers. In the optical path setting process, it is determined whether or not an optical path can be set between the two nodes selected in the node selection process with respect to the new optical path topology. On the other hand, if the setting is impossible, the node selection process is performed again. In the determination process, it is determined whether the optical path assignment to all of the transmission / reception interfaces included in the plurality of nodes is completed. If the optical path assignment is not completed, the node selection process is performed. It is determined whether the topology is a connected graph or a disconnected graph. As a result of the determination, in the case of a connected graph, the new optical path topology generation process is terminated, whereas in the case of a disconnected graph, the initialization process is performed again.

  The optical path topology comparison process compares the new optical path topology with the working optical path topology. If the new optical path topology is superior to the working optical path topology, the new optical path topology is selected as the optimum optical path topology. To replace the working optical path topology.

  The end condition recorded in the storage device in advance is read, and the new optical path topology generation process and the optical path topology comparison process are repeated until the end condition is satisfied.

  Further, the optimum optical path search method according to the second invention includes a plurality of nodes arranged in a mesh shape, an optical fiber that connects adjacent nodes and transmits a wavelength-multiplexed optical signal, and each of the plurality of nodes. An initialization process, an optical path setting process, and an IP path topology, which are performed when shifting from an active optical path topology to an optimal optical path topology in a meshed wavelength division multiplexing optical network including connected optical path setting apparatuses. A setting process, an optical path releasing process, and an optical path resetting process are provided.

  In the initialization process, a new optical path topology is initialized. In the optical path setting process, for the new optical path topology, after setting the optical path between adjacent nodes, until the allocation of the optical path to all transmission / reception interfaces of the node is completed, the traffic starts from the traffic in descending order. Set the optical path. In the IP path topology setting process, an IP path topology is set for the new optical path topology. In the optical path release process, the optical paths are released in ascending order of traffic in the IP path topology until the new optical path topology becomes a disconnected graph. In the optical path resetting process, an optical path is set for a new optical path topology using resources obtained by releasing the optical path.

  When the new optical path topology is compared with the working optical path topology and the new optical path topology is superior to the working optical path topology, the working optical path topology is replaced with the new optical path topology, and then the IP path Each process from the topology setting process to the optical path resetting process is repeated.

  According to the optimum optical path search method of the first invention, the optical path is set based on the traffic between the nodes, so that an appropriate optical path topology can be obtained for the current traffic distribution. Further, by setting an optical path using random numbers, it is possible to search for the best optical path topology at high speed without searching for optical path topologies of all patterns.

  Further, according to the optimum optical path search method of the second invention, after the optical path topology is made into a connected graph, the path with less traffic is released, and as a result, the optical path with much traffic is obtained using the obtained resources. Therefore, the best optical path topology can be searched efficiently.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, each component and the arrangement relationship are merely schematically shown to the extent that the present invention can be understood. In the following, a preferred configuration example of the present invention will be described. However, numerical conditions and the like are merely preferred examples. Therefore, the present invention is not limited to the following embodiment.

(Network configuration)
FIG. 1 is a schematic configuration diagram for explaining a network (hereinafter referred to as an internal network) that implements the optical path search method of the present invention. The internal network is an optical fiber (hereinafter, referred to as “N”) that connects a plurality of nodes (hereinafter also referred to as “N”) arranged in a mesh shape or a lattice shape and connects adjacent nodes to each other and transmits a wavelength multiplexed optical signal. And an optical path setting device 200 connected to each of a plurality of nodes constituting the internal network. The optical path setting device 200 is connected to each node by a control signal line network 400.

  Here, although an internal network is demonstrated as what is comprised by six nodes, it is not limited to six at all. Each of these nodes is assigned a unique node ID. Here, the node ID is a natural number from 1 to 6. For example, N1 indicates a node whose node ID is 1.

  The nodes N1 to N6 are arranged in a 2 × 3 mesh form in the network topology, and adjacent nodes are physically connected by optical fibers. Each of these optical fibers is assigned a unique fiber ID. Here, the fiber ID is a natural number from 1 to 7. For example, F1 represents an optical fiber whose fiber ID is 1. Note that the number of optical fibers constituting the internal network is determined by the number of nodes and their arrangement, and is not limited to seven. The optical fibers F1 to F7 can communicate bidirectionally between adjacent nodes, and can transmit a wavelength-multiplexed optical signal obtained by multiplexing a plurality of optical signals having different wavelengths by wavelength multiplexing.

  Here, one optical fiber that physically connects adjacent nodes may be provided one by one, and a configuration for performing bidirectional wavelength division multiplexing communication may be employed, or two or more optical fibers may be provided, and each optical fiber may be unidirectional. The wavelength multiplex communication may be performed. The optical fiber can have any suitable configuration depending on settings such as the wavelength used.

(Node configuration)
The configuration of the node will be described with reference to FIG. FIG. 2 is a schematic configuration diagram for explaining the configuration of the node, and here, a configuration example of N1 is shown as an example. The node (N1) includes an optical processing unit 110 and an electrical processing unit 150. The optical processing unit 110 further includes an input side optical amplifier 112, an output side optical amplifier 113, an input side optical filter 114, an output side optical filter 115, an optical switch unit 116, an electric / optical (E / O) converter 122, an optical An electrical / electrical (O / E) converter 124 and an optical switch control unit 126 are provided. The electrical processing unit 150 includes a router 152 and a traffic measurement unit 154.

  N1 receives a wavelength-multiplexed optical signal from N2 that is an adjacent node via F1 that is an optical fiber that connects N1 and N2. N1 receives a wavelength-multiplexed optical signal from N6, which is an adjacent node, via F6, which is an optical fiber that connects N1 and N6. The optical processing unit 110 includes an input side optical amplifier 112 and an input side optical filter 114 for each optical fiber.

  The first input-side optical amplifier 112a amplifies the wavelength multiplexed optical signal received via F1, and then sends it to the first input-side optical filter 114a. The second input-side optical amplifier 112b amplifies the wavelength multiplexed optical signal received through F6, and then sends it to the second input-side optical filter 114b.

  Here, the wavelength-multiplexed optical signal is described as being obtained by multiplexing four types of wavelengths, but is not limited to four types. Each of these four types of wavelengths is assigned a unique wavelength ID, and the wavelength ID is a natural number. In the following description, the wavelength is represented by λ. For example, λ1 indicates a wavelength having a wavelength ID of 1.

  The first input-side optical filter 114a separates the wavelength multiplexed optical signal into optical signals of four wavelengths, for example, λ1, λ2, λ3, and λ4, for each wavelength. The separated optical signals of respective wavelengths are sent to the optical switch unit 116.

  The second input-side optical filter 114b separates the wavelength multiplexed optical signal into optical signals of four wavelengths, for example, λ5, λ6, λ7, and λ8, for each wavelength. The separated optical signals of respective wavelengths are sent to the optical switch unit 116.

  The optical signal of each wavelength sent to the optical switch unit 116 is, for example, between a pass (cut-through) state and a drop state by an optical cross connect (OXC) device provided in the optical switch unit 116. Change over. Here, the cut-through state is a state in which the optical signal input from the input side optical filter 114 passes through the node without passing through the router 152 and is sent to the adjacent node, that is, the node is passed through. It is. The drop state is a state in which the optical signal input from the optical filter 114 is photoelectrically converted by the O / E converter 124 and sent to the router 152 as an electrical signal.

  The optical switch unit 116 includes a 2 × 2 optical switch that is an OXC device for each optical signal separated by the input-side optical filter 114. Here, since the input-side optical filter 114 separates the optical signals having eight different wavelengths λ1 to λ8, the optical switch unit 116 may include first to eighth 2 × 2 optical switches. it can. In FIG. 2, the first 2 × 2 optical switch 117 is representatively shown.

  Further, an E / O converter 122 and an O / E converter 124 are provided corresponding to the first to eighth 2 × 2 optical switches. In this example, since the optical switch unit 116 includes first to eighth 2 × 2 optical switches, the optical processing unit 110 includes first to eighth E / O converters 122a to 122h, Eight O / E converters 124a to 124h are provided. The first to eighth E / O converters 122a to 122h convert electrical signals into optical signals having wavelengths λ1 to λ8, respectively. The first to eighth O / E converters 124a to 124h convert optical signals having wavelengths λ1 to λ8 into electrical signals, respectively.

  The first 2 × 2 optical switch 117 includes two input terminals Ia and Ib and two output terminals Oa and Ob. The input terminal Ia of the first 2 × 2 optical switch 117 is connected to the first input-side optical filter 114a, and receives the optical signal having the wavelength λ1 separated by the first input-side optical filter 114a. The input terminal Ib is connected to the first E / O converter 122a. The output terminal Oa is connected to the first output-side optical filter 115a and transmits an optical signal having a wavelength λ1 to the first output-side optical filter 115a. The output terminal Ob is connected to the first O / E converter 124a.

  The state in which the input terminal Ia and the output terminal Oa are connected and the input terminal Ib and the output terminal Ob are connected is a cut-through state. In the cut-through state, an optical signal input from the first input side optical filter 114a via the input terminal Ia is output to the first output side optical filter 115a via the output terminal Oa.

  On the other hand, the state in which the input terminal Ia and the output terminal Ob are connected and the input terminal Ib and the output terminal Ob are connected is a drop state. In the drop state, the optical signal having the wavelength λ1 input from the first input-side optical filter 114a via the input terminal Ia is sent to the first O / E converter 124a via the output terminal Ob. The first O / E converter 124 a converts the optical signal having the wavelength λ <b> 1 into an electrical signal and then sends the electrical signal to the electrical processing unit 150. The first E / O converter 122a converts the electrical signal received from the electrical processing unit 150 into an optical signal having the wavelength λ1, and then transmits the optical signal to the first 2 × 2 optical switch 117. The optical signal input through the input terminal Ib of the first 2 × 2 optical switch 117 is sent to the first output-side optical filter 115a through the output terminal Oa.

  The router 152 analyzes the header of the packet included in the electrical signal converted from the optical signal by the O / E converter 124 or the packet received from the external network 300 and sends the packet to the external network 300, or the internal Decide whether to send to the network. A packet sent to the internal network is converted into an optical signal by the E / O converter 122 and then sent to the optical switch unit 116. Further, from each 2 × 2 optical switch of the optical switch unit 116, an output side optical filter 115. The optical signal of each wavelength is wavelength-multiplexed by the output-side optical filter 115, amplified by the output-side optical amplifier 113, and sent to the adjacent node. The optical processing unit 110 includes an output side optical filter 115 and an output side optical amplifier 113 for each optical fiber. The wavelength multiplexed optical signal amplified by the first output side optical amplifier 113a is sent to N6 via F6. The wavelength multiplexed optical signal amplified by the second output side optical amplifier 113b is sent to N2 via F1.

  The traffic measurement unit 154 included in the electrical processing unit 150 is connected between the router 152 and the E / O converter 122 and the O / E converter 124 of the optical processing unit 110, and is connected to one router and another router. Measure incoming and outgoing traffic. The measurement result is transmitted to the optical path setting device 200 via the control signal line network 400. As the traffic measurement unit 154, any suitable known one can be used. A configuration in which the router 152 is connected to the external network 300 may be employed.

  The optical switch control unit 126 switches the optical switch unit 116 in response to a control signal received from the optical path setting device 200 via the control signal line network 400. Specifically, by switching the 2 × 2 optical switch included in the optical switch unit 116, the optical signal is switched between the cut-through state and the drop state, and the transmission destination node is changed.

  The control signal received from the optical path setting device 200 via the control signal line network 400 is also sent to the router 152, and the router 152 switches the IP path in response to the control signal.

(First embodiment)
With reference to FIG. 3, the configuration of the optical path setting device of the first embodiment will be described. FIG. 3 is a schematic configuration diagram of the optical path setting device 200. The optical path setting apparatus 200 can use a known computer or the like that includes the input / output interface 202, the input / output unit 206, the storage unit 210, and the MPU (Microprocessing Unit) 220. The input / output unit 206 includes a known input device such as a keyboard and a mouse normally used in a computer, and an output device such as a display and a printer. As the storage unit 210, any suitable known storage device such as a hard disk is used. The MPU 220 may have a well-known configuration. In this example, the MPU 220 includes a central processing unit (CPU) 230, a RAM (Random Access Memory) 222 as a memory, and a ROM (Read Only Memory) 224. Yes.

  The control unit 232 included in the CPU 230 reads out a program recorded in a readable manner in the ROM 224 and executes the program, thereby functioning as the function unit 240, the transmission processing unit 244, the end condition determination unit 246, the IP path search. Means 248, traffic calculation means 250, optical path topology evaluation means 252, optical path topology table reading means 254, and new optical path topology generation means 260 are realized. The new optical path topology generation unit 260 further includes a random number generation unit 262, a node selection unit 264, a route selection unit 266, an interface assignment determination unit 270, a connection determination unit 272, an initialization unit 274, and an optical path setting unit 276. I have. Details of processing in each functional unit will be described later.

  With reference to FIGS. 4 and 5, the optimum optical path topology search method of the first embodiment will be described. FIG. 4 is a process flow diagram for explaining a search method of the optimum optical path topology. FIG. 5 is a process flow diagram for explaining a new optical path topology generation process executed in the search for the optimum optical path topology.

  The traffic calculation means 250 monitors the traffic information and receives the traffic measurement results at each node via the input / output interface 202 at preset time intervals. Based on the received traffic measurement results, the traffic calculation means 250 creates a table of traffic sent and received between nodes (hereinafter also referred to as a traffic matrix) as traffic information. FIG. 6 is a diagram for explaining a traffic matrix. In this traffic matrix 218, for each node of the transmission source (node included in the column indicated by 218a in the figure), traffic to each node of the transmission destination (node included in the column indicated by 218b in the figure) Shown in matrix form. Accordingly, when one node is selected from each node of the transmission source and each node of the transmission destination, traffic from the transmission source node to the transmission destination node can be obtained. This traffic matrix is stored in the RAM 222 or the storage unit 210 so as to be readable, but here it will be described as being stored in the storage unit 210.

  In step (hereinafter, step is represented by S) 10, the optical path topology table reading unit 254 reads the optical path topology table 214 stored in the storage unit 210 so as to be readable and rewritable. The optical path topology table 214 is a table showing the setting state of the optical path in the internal network, and the optical path topology table 214 includes nodes at both ends for each optical path and an optical fiber through which an optical signal propagating through the optical path passes. And the node, the set wavelength, and the like are recorded. The optical path topology indicated by the optical path topology table 214 is referred to as a working optical path topology.

  In S <b> 20, the end condition determination unit 246 reads the end condition 216 stored in advance in the storage unit 210 so as to be readable. The end condition 216 can be arbitrarily set appropriately, such as the time for performing the processing in the optical path setting device 200 or the number of executions of a process for generating a new optical path topology described later. The termination condition determination unit 246 makes a determination based on the termination condition 216. When the termination condition is satisfied, the optimum optical path topology search process is terminated. On the other hand, if the termination condition is not satisfied, the new optical path topology generation process of S30 is subsequently performed.

  The new optical path topology generation process of S30 is executed by the new optical path topology generation means 260, and further includes the processes of S110 to S170.

  In the initialization process of S110, the new optical path topology is initialized. In this process, the initialization unit 274 provided in the new optical path topology generation unit 260 initializes the new optical path topology. If the new optical path topology table does not exist in the storage device such as the RAM 222, a new optical path topology table is newly created. On the other hand, if it already exists, the new optical path topology table indicated by the new optical path topology table is An optical path is not set between any of the nodes N1 to N6.

  In the node selection process of S120, two nodes are selected using random numbers. In this process, first, the random number generation unit 262 generates two random numbers having the maximum number of interfaces included in each node as a maximum value. Here, the number of interfaces is the number of optical signals that can be used by each node, and is determined by, for example, the number of O / E converters 122 included in the optical processing unit 110. The random number is generated by any suitable known method, for example, by reading a random number table stored in the ROM 224 or the like in a freely readable manner. Next, the node selection unit 264 selects a node corresponding to each of the two random numbers generated by the random number generation unit 262. In addition, when the node corresponding to each of two random numbers is the same, it can be set as the structure which produces | generates a random number again.

  In the optical path setting process of S130, S140 and S150, it is determined whether or not an optical path can be set for the new optical path topology between the two nodes selected in the node selection process. An optical path is set between them, and if it cannot be set, a node selection process is performed.

  In S130, the route selection unit 266 selects a route between the two nodes selected in the node selection process in S120. The route selection unit 266 first reads the physical topology table 212 stored in the storage unit 210 so as to be readable. The physical topology table 212 indicates a physical connection state of optical fibers between nodes. Next, the route selection unit 266 refers to the physical topology table 212 and selects a route. As a method for selecting a route, for example, a shortest route search method called a Dijkstra method can be used. Here, the shortest route refers to a route having the smallest number of nodes (hereinafter also referred to as passing nodes) that pass through. When there are a plurality of routes having the same number of transit nodes, one route is randomly selected from the plurality of routes.

  In S140, the optical path setting unit 276 determines whether an optical path can be set in the route selected in S130. The optical path setting unit 276 reads the constraint condition 217 stored in the storage unit 210 so as to be read and rewritten. In the constraint condition 217, the number of wavelengths that can be used in each optical fiber and each node is recorded. The optical path setting unit 276 refers to the constraint condition 217 and the new optical path topology table, and checks the wavelengths that can be used in the route selected in S130. If there is no usable wavelength, it is determined that the optical path cannot be set, and the node selection process of S120 is performed.

  If there is a usable wavelength, the optical path setting unit 276 updates the new optical path topology in S150. Here, the new optical path topology is updated by newly writing, in the new optical path topology table, two nodes to which the optical path is set, optical fibers and nodes that pass through, and assigned wavelengths.

In the determination process of S160 and S170, it is determined whether or not the optical path assignment to all of the transmission / reception interfaces included in the plurality of nodes is completed. If not completed, the node selection process of S120 is performed. In the case of a connected graph, it is further determined whether or not the new optical path topology is a connected graph. In the case of a disconnected graph, an initialization process is performed. In the case of a connected graph, the new optical path topology generation process is terminated. In S160, the interface assignment determination unit 270 compares the number of optical paths written in the new optical path topology table with the total number of interfaces included in each node to determine whether or not optical paths are assigned to all interfaces. Judgment is made. As a result of this determination, if there is an interface to which an optical path is not yet allocated, the node selection process of S120 is performed. Note that when a random number is generated in S120, an interface to which an optical path has already been assigned is excluded.

  If there is no transmission / reception interface to which no optical path is assigned, in S170, the connection determination unit 272 determines whether the optical path topology is a connected graph or a disconnected graph. Here, the optical path topology being a connected graph means that there is a path from a certain node to all other nodes starting from a certain node. In addition, the path | route between two nodes is not only set with one optical path, The structure set using two or more optical paths via another node may be sufficient. The optical path topology is not connected graph refers to a state in which there are nodes in the network that cannot be reached from the starting node, that is, a state in which the network is divided.

  As a result of the above determination, if the optical path topology is a disconnected graph, it is determined that the created optical path topology is not applicable, and the processes from S110 to S170 are performed again.

  If the optical path topology is a connected graph, an optical path topology comparison process is performed in S40 to S80. The optical path topology comparison process compares the new optical path topology with the working optical path topology. If the new optical path topology is superior to the working optical path topology, the new optical path topology is selected as the optimum optical path topology. To replace the working optical path topology.

  In S40, the IP path search means 248 sets an IP path between the nodes. In setting the IP path, for example, the shortest IP path is selected using the Dijkstra method. Here, the shortest IP path refers to a route having the smallest number of relaying nodes. In setting the shortest IP path, it is possible to select an IP path with the shortest transmission time in consideration of the transmission amount of the fiber transmitting the optical signal. The IP path setting result between the nodes is recorded in the storage unit 210 as an IP path topology table 215 so that it can be read and written.

  In S50, the traffic calculation unit 250 applies the traffic matrix 218 (see FIG. 6) read from the storage unit 210 to the IP path topology table 215 created in S40, and calculates the traffic relayed at each node. . For example, when the IP path between N1 and N5 and the IP path between N3 and N6 are both relayed by N2, the traffic between N1 and N5 is 6 (= 6 + 0), and the traffic between N3 and N6 is Since 26 (= 18 + 8), the traffic relayed by N2 is 32.

  In S <b> 60, the optical path topology evaluation unit 252 refers to the objective function recorded in the storage unit 210 or the ROM 224 and evaluates the optical path topology. Here, as the objective function, for example, a function for obtaining the sum of traffic relayed at each node calculated in S50 as an evaluation result can be used.

  In S70, the optical path topology evaluation unit 252 compares the evaluation result of the optical path topology indicated by the new optical path topology table with the evaluation result of the working optical path topology. As a result of the comparison, if the evaluation result of the new optical path topology is superior to the evaluation result of the working optical path topology, for example, if the traffic relayed at each node is small, the new optical path topology is determined as the optimum light in S80. After replacing the working optical path topology as the path topology, the termination condition of S20 is determined. At this time, the new optical path topology table is stored in the storage unit 210 as an optical path topology table. If the evaluation result of the new optical path topology does not improve, the termination condition of S20 is determined with the working optical path topology unchanged.

  After the above process is completed and the optical path topology search flow is completed, the transmission processing unit 244 transmits the optical path topology of each node so that the optical path topology indicated by the optical path topology table 214 stored in the storage unit 210 is obtained. The optical path and IP path control signals are transmitted to the switch control unit and the router to change the settings.

  According to the optimal optical path search method of the first embodiment, since an optical path is set based on traffic between nodes, an appropriate optical path topology can be obtained for the current traffic distribution. Further, by setting an optical path using random numbers, it is possible to search for the best optical path topology at high speed without searching for optical path topologies of all patterns.

(Second Embodiment)
With reference to FIG. 7, the structure of the optical path setting apparatus of 2nd Embodiment is demonstrated. FIG. 7 is a schematic configuration diagram of the optical path setting device 201. As the optical path setting device 201, a known computer or the like that includes the input / output interface 202, the input / output unit 206, the storage unit 210, and the MPU 220 can be used. The MPU 220 may have a known configuration, and here, the MPU 220 includes a CPU 230, a RAM 222 and a ROM 224 as memories.

  The control means 232 included in the CPU 230 reads out a program recorded in a readable manner in the ROM 224 or the like and executes the program to thereby function as the function means 240 as a transmission processing means 244, an IP path search means 248, a traffic calculation means. 250, an optical path releasing unit 255, an optical path resetting unit 256, and a new optical path topology generating unit 261 are realized. The new optical path topology generation unit 261 further includes a random number generation unit 262, a node pair rearrangement unit 263, a route selection unit 266, an interface assignment determination unit 270, an initialization unit 274, an optical path setting unit 276, and a node pair selection unit 278. It has. Note that components having the same reference numerals as those of the optical path setting device of the first embodiment described with reference to FIG. 3 are the same as those described in the first embodiment, and thus description thereof is omitted. Details of processing in each functional unit will be described later.

  With reference to FIG. 8 and FIG. 9, the search method of the optimum optical path topology of the second embodiment will be described. FIG. 8 is a process flow diagram for explaining a method for generating a new optical path topology, which is executed in the search for the optimum optical path topology according to the second embodiment. FIG. 9 is a process flowchart for explaining the optimum optical path topology search process of the second embodiment.

  In the initialization process of S210, the new optical path topology is initialized. In this process, the initialization unit 274 provided in the new optical path topology generation unit 261 initializes the new optical path topology. If the new optical path topology table does not exist in the storage device such as the RAM 222, a new optical path topology table is newly created. If the new optical path topology table already exists, the new optical path topology table indicated by the new optical path topology table is An optical path is not set between any of the nodes N1 to N6.

  In the optical path setting process of S212, the optical paths are set in order from the largest traffic until the allocation of the optical paths to all transmission / reception interfaces of the node is completed. In this process, the optical path setting unit 276 sets an optical path between physically adjacent nodes. The optical path setting unit 276 first reads the physical topology table 212 stored in the storage unit 210 so as to be freely read. The optical path setting means 276 refers to the physical topology table 212 and sets an optical path between physically adjacent nodes. As a result, the two nodes in which the optical path is set in the new optical path topology table , Newly write the assigned wavelength and the like. By setting an optical path between adjacent nodes, the optical path topology becomes a connected graph.

  In the optical path setting process of S215, S260, S222, S230, S240, S250, and S265, the optical path is set in order from the largest traffic until the allocation of the optical path to all transmission / reception interfaces of the node is completed. .

  In S260, the interface assignment determination unit 270 determines whether or not optical paths are assigned to all the transmission / reception interfaces. If there is an interface to which an optical path is not yet assigned as a result of this determination, a process of selecting a node pair in S222 is performed. When there is an interface to which an optical path is already assigned, the interface is selected except for the interface. If there is no interface to which no optical path is assigned, the new optical path topology is updated in S265. Here, the new optical path topology table is stored in the storage unit 210, the RAM 222, or the like so as to be readable and writable.

  In S215, the node pair rearranging unit 263 reads the traffic matrix (see FIG. 6) and creates a traffic table. An example of a traffic table created from the traffic matrix is shown in FIG. The node pair rearrangement unit 263 selects two different nodes from the traffic matrix, and calculates traffic between the two nodes. For example, when N1 and N2 are selected, the traffic from N1 to N2 is 0, and the traffic from N2 to N1 is also 0, so the traffic between N1 and N2 is 0 + 0 = 0. In this way, the traffic table 219a is created by calculating the traffic between the nodes.

  Next, the node pair rearranging means 263 rearranges the traffic table 219a. In this rearrangement, the node pairs are rearranged in descending order of traffic. FIG. 10B shows a traffic table 219b as a result of the rearrangement.

  In S222, the node pair selection unit 278 selects the node pair with the largest traffic. Here, a pair of N3 and N6 is selected.

  In S230, the route selection unit 266 sets a route between the node pair selected in S222. The route is set by referring to the physical topology table 212 and selecting a route. There are a plurality of paths that can set an optical path between nodes. Here, the shortest path is selected using a shortest path search method called a Dijkstra method. Here, the shortest route refers to a route having the smallest number of nodes (hereinafter also referred to as passing nodes) that pass through. For example, when the node pair is N3 and N6, there are three types of shortest paths between N3 and N6: N3-N2-N1-N6, N3-N2-N5-N6, and N3-N4-N5-N6. When there are a plurality of paths that are the shortest paths in this way, a path with a low wavelength multiplicity in the passing optical fiber is selected with priority. When there are a plurality of shortest paths under the same condition, one path may be selected at random as described in the first embodiment. The selection of this path is performed using, for example, a random number generated by the random number generation unit 262.

  In S240, the optical path setting unit 276 determines whether an optical path can be set in the route selected in S230. The optical path setting unit 276 reads the constraint condition 217 stored in the storage unit 210 so as to be read and rewritten. In the constraint condition 217, the wavelength set for each optical fiber and the number of wavelengths that can be used in each optical fiber and each node are recorded. The optical path setting unit 276 refers to the constraint condition 217 and checks the wavelengths that can be used in the route selected in S230. If there is no usable wavelength, it is determined that an optical path cannot be set, and a process of selecting a node pair in S222 is performed.

  If there is a usable wavelength, an optical path is added to the new optical path topology in S250. In the new optical path topology table, for the added optical path, two nodes to which the optical path is set, an optical fiber and a node that pass through, an assigned wavelength, and the like are written.

  After the new optical path topology is generated in the process up to S265 described with reference to FIG. 8, the IP path topology is set in the IP path topology setting process in S310 and S320.

  In S310, the optical path topology evaluation unit 252 reads a new optical path topology table stored in the storage unit 210, the RAM 222, or the like so as to be read and rewritten.

  In S320, the IP path search means 248 sets the IP path topology. In setting the IP path topology, for example, the shortest IP path is selected using a shortest path search method called a Dijkstra method. In this case, the shortest IP path refers to a route having the smallest number of relaying nodes. In selecting the shortest IP path, it is also possible to adopt a configuration in which the IP path with the shortest transmission time is selected in consideration of the transmission amount of the fiber transmitting the optical signal. The IP path setting result between the nodes is recorded in the storage unit 210 as an IP path topology table 215 so that it can be read and written.

  In the optical path cancellation process of S330, S340, and S370, the optical path cancellation unit 255 releases the optical paths in order from the smallest traffic in the IP path topology until the new optical path topology becomes a disconnected graph.

  In S330, the traffic calculation means 250 applies the traffic matrix 218 to the IP path topology table 215 created in S320, and calculates the traffic in each optical path. Thereafter, the optical paths are rearranged in ascending order of traffic based on the calculation result of the traffic in each optical path.

  This traffic corresponds to the utilization rate of the optical path. In S340, the optical path with the least traffic, that is, the low utilization rate is released.

  After canceling the traffic, in S370, the optical path cancellation unit 255 determines whether the new optical path topology is a connected graph or a disconnected graph. If the result of this determination is that the new optical path topology is a connected graph, the process of S340 is performed again, and the optical path releasing means 255 releases the optical path with the least traffic among the set optical paths. . The processes of S340 and S370 are repeated until the new optical path topology becomes a disconnected graph.

  After the new optical path topology becomes a disconnected graph, the optical path is set using the resources obtained by releasing the optical path in the optical path releasing process in the optical path resetting process of S380. Is called. First, the optical path resetting unit 256 selects a node pair with the largest traffic, and then sets a path between the selected node pairs. In setting the route, the route is selected with reference to the physical topology table 212. There are a plurality of paths that can set an optical path between nodes. Here, the shortest path is selected using a shortest path search method called a Dijkstra method. Here, the shortest route is a route having the smallest number of passing nodes. When there are a plurality of shortest paths, a path with a low wavelength multiplicity in the passing optical fiber is selected with priority. When there are a plurality of shortest paths under the same condition, one path may be selected at random as described in the first embodiment. Next, it is determined whether an optical path can be set for the selected route. As a result of examining the wavelengths that can be used in the selected route, if there is no usable wavelength, it is determined that the optical path cannot be set, and the node pair with the next largest traffic is selected, and the optical path in S380 is again performed. Perform the reconfiguration process.

  The optical path resetting process is performed until optical paths are assigned to all transmission / reception interfaces.

  After the optical path resetting process, the newly set optical path topology is evaluated in S390, S400, S410, and S420.

  In S390, the IP path search means 248 sets the IP path topology between the nodes. The setting of the IP path topology is the same as the IP path topology setting process in S320, and thus description thereof is omitted.

  In S400, the traffic calculation unit 250 applies the traffic matrix 218 read from the storage unit 210 to the IP path topology table 215 created in S390, and calculates the traffic relayed at each node.

  In S410, the optical path topology evaluation unit 252 refers to the objective function recorded in the storage unit 210 or the ROM 224 and evaluates the optical path topology. Here, the objective function can be, for example, a function for obtaining the sum of traffic relayed at each node calculated in S400 as an evaluation result.

  In S420, the optical path topology evaluation unit 252 compares the evaluation result of the optical path topology indicated by the new optical path topology table with the evaluation result of the working optical path topology. As a result of the comparison, if the evaluation result of the new optical path topology is superior to the evaluation result of the active optical path topology, for example, if the traffic relayed at each node is small, the new optical path topology update unit 269 is performed in S430. Updates the new optical path topology table as the optical path topology table, stores it in the storage unit 210, and then repeats the process from S320 to S430. If the evaluation result of the new optical path topology does not improve, the search process is terminated with the working optical path topology.

  After the above process is completed and the optical path topology search flow is completed, an optical path control signal is transmitted from the transmission processing means 244 to the optical switch control unit of each node.

  In addition, according to the optimum optical path search method of the second embodiment, after the optical path topology is connected to the connected graph, the path with less traffic is released, and as a result, the optical path with much traffic is obtained using the obtained resources. Therefore, the best optical path topology can be searched efficiently.

It is a schematic block diagram for demonstrating an internal network. It is a schematic block diagram for demonstrating a node. It is a schematic block diagram for demonstrating the optical path setting apparatus of 1st Embodiment. It is a processing flow figure for demonstrating the search method of the optimal optical path topology of 1st Embodiment. It is a processing flow figure for demonstrating the production | generation process of the novel optical path topology in 1st Embodiment. It is a figure for demonstrating a traffic matrix. It is a schematic block diagram for demonstrating the optical path setting apparatus of 2nd Embodiment. It is a processing flowchart for demonstrating the production | generation process of the new optical path topology in 2nd Embodiment. It is a processing flowchart for demonstrating the search method of the optimal optical path topology of 2nd Embodiment. It is a figure for demonstrating a traffic table.

Explanation of symbols

DESCRIPTION OF SYMBOLS 110 Optical processing part 112 Input side optical amplifier 113 Output side optical amplifier 114 Input side optical filter 115 Output side optical filter 116 Optical switch part 117 1st 2 * 2 optical switch 122 E / O converter 124 O / E converter 126 Optical switch control unit 150 Electrical processing unit 152 Router 154 Traffic measurement unit 200, 201 Optical path setting device 202 Input / output interface 206 Input / output unit 210 Storage unit 216 End condition 217 Restriction condition 218 Traffic matrix 219a, 219b Traffic table 220 MPU
222 RAM
224 ROM
230 CPU
232 Control unit 240 Function unit 244 Transmission processing unit 246 Termination condition determination unit 248 IP path search unit 250 Traffic calculation unit 252 Optical path topology evaluation unit 254 Optical path topology table reading unit 255 Optical path release unit 256 Optical path resetting unit 260 261 New optical path topology generation unit 262 Random number generation unit 263 Node pair rearrangement unit 264 Node selection unit 266 Route selection unit 269 New optical path topology update unit 270 Interface allocation determination unit 272 Connection determination unit 274 Initialization unit 276 Optical path setting unit 278 Node pair Selection means 300 External network 400 Control signal line network

Claims (2)

A mesh comprising: a plurality of nodes arranged in a mesh; an optical fiber for transmitting a wavelength-multiplexed optical signal by connecting adjacent nodes; and an optical path setting device connected to each of the plurality of nodes In a wavelength division multiplexing optical network, a method for searching for an optimal optical path topology when shifting from an active optical path topology to an optimal optical path topology,
New optical path topology generation process for generating a new optical path topology;
When the new optical path topology is superior to the working optical path topology when the new optical path topology is compared with the working optical path topology, the new optical path topology is set as the optimum optical path topology. It has an optical path topology comparison process that replaces the working optical path topology,
The new optical path topology generation process includes:
An initialization process to initialize a new optical path topology;
A node selection process for selecting two nodes using random numbers;
For the new optical path topology, it is determined whether an optical path between the two nodes selected in the node selection process can be set, and if so, an optical path is set between the two nodes; On the other hand, if the setting is impossible, the optical path setting process for performing the node selection process again,
It is determined whether the assignment of optical paths to all of the transmission / reception interfaces included in the plurality of nodes is completed. If the optical path allocation is not completed, the node selection process is performed. It is determined whether the graph is a connected graph or a disconnected graph, and in the case of a connected graph, a new optical path topology generation process is terminated, while in the case of a disconnected graph, a determination process is performed in which an initialization process is performed again. ,
An optimum optical path search method comprising: reading an end condition recorded in advance in a storage device; and repeatedly performing the new optical path topology generation process and the optical path topology comparison process until the end condition is satisfied. . A mesh comprising: a plurality of nodes arranged in a mesh; an optical fiber for transmitting a wavelength-multiplexed optical signal by connecting adjacent nodes; and an optical path setting device connected to each of the plurality of nodes In a wavelength division multiplexing optical network, a method for searching for an optimal optical path topology when shifting from an active optical path topology to an optimal optical path topology,
An initialization process to initialize a new optical path topology;
After the optical path is set between adjacent nodes for the new optical path topology, the optical paths are set in order from the largest traffic until the optical path assignment is completed for all the transmission / reception interfaces of the node. Path setting process,
IP path topology setting process for setting an IP path topology for a new optical path topology;
Until the new optical path topology becomes a disconnected graph, the optical path cancellation process of canceling the optical path in order from the smallest traffic in the IP path topology;
An optical path resetting process for setting an optical path for the new optical path topology using resources obtained by releasing the optical path;
When the new optical path topology is compared with the working optical path topology and the new optical path topology is superior to the working optical path topology, the working optical path topology is replaced with the new optical path topology. An optimal optical path search method characterized by repeatedly performing each process from an IP path topology setting process to an optical path resetting process after replacement.

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