JP2015204623A - Hierarchical induction search of n-tuple separated optical path - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hierarchical induction search capable of evaluating an optical path in an optical network.SOLUTION: In order to select a desired system of regenerator, the hierarchical induction search uses a matrix M to determine a group having an available regenerator and to obtain an available end-end optical path. The hierarchical induction search may be used to efficiently select a desired N-tuple separated optical path from available optical paths. The hierarchical induction search may use a search graph and a search tree to induce a search and to delete a candidate node and an optical path at an earlier stage of the search processing.

Description

  The present disclosure relates generally to optical communication networks, and more particularly to hierarchical guided search of N-tuple separated optical paths.

  Telecommunications systems, cable television systems, and data communication networks use optical networks to quickly transfer large amounts of information between remote locations. In an optical network, information can be conveyed in the form of optical signals through optical fibers. An optical network may have various network components configured to perform various operations within the network, such as amplifiers, dispersion compensators, multiplexer / demultiplexer filters, wavelength selective switches, couplers, and the like. .

  The function of calculating optical signal paths through various network elements is a core function for the design, modeling, management and control of optical networks. Optical path computation may allow optical network operators to customize, control and update network policies. One feature of the optical path calculation involves the determination of an end-to-end reachable optical path from the source node to the destination node. When the source node and the destination node are determined to be “directly reachable”, one or more paths that are all optical paths exist in the optical network between the source node and the destination node.

  In the absence of direct reachability from the source node to the destination node, the optical signal is electrically transmitted along a given signal path using an optical-electrical-optical (OEO) regenerator. Will be replayed. This involves a great deal of network resources and is not very cost effective. When a regenerator is used, the end-to-end reachable path may have a certain number of regenerators between the source node and the destination node. Thus, one difficult goal in optical path calculation is to find an end-to-end reachable path with a minimum or specified number of regenerators, and other such as, for example, a desired level of signal latency or cost. Satisfying route constraints. For example, US patent application Ser. No. 14 / 169,980, filed Jan. 31, 2014, uses the reachability matrix and the use of transitive closure properties on matrix operations to determine regenerator node locations. Disclose. However, the amount of memory consumed during the computation of a series of reachable matrices can represent computational efficiency or computational feasibility.

  The disclosed embodiments provide techniques for the evaluation of optical paths in an optical network.

  In one aspect, the disclosed method is for evaluation of an optical path within an optical network. Based on a matrix M that includes all optical path reachability information of nodes in the optical network, the method may include generating a set of all optical paths between the source node and the destination node. The all-optical path may have a minimum number of regenerators between the source node and the destination node. The set of all optical paths may be grouped according to the regenerator stage. The method may further comprise generating path cost information for the set of all optical paths. The path cost information may include a cost metric for each all-optical path. Based on the path cost information, the method may further comprise calculating node cost information for each node associated with all optical paths to the destination node, excluding the destination node. The method is a step of generating a hierarchical guided search graph, wherein the hierarchical guided search graph includes a set of all optical paths, an optical path group having optical paths between common nodes, path cost information, and node cost information. There may be a step having an associated node. Based on the hierarchical guided search graph, the method may include determining a lowest cost optical path between the source node and the destination node.

  In any of the disclosed embodiments, the step of determining the lowest cost optical path between the source node and the destination node is from the source node in the hierarchical guided search graph. Starting and evaluating an optical path group from each node to each successive regenerator stage toward the destination node in the hierarchical guided search graph based on the path cost information and the node cost information. And further comprising the step of selecting the next optical path to the next regenerator stage.

  Further, the disclosed aspects may include a path calculation engine for calculation of optical paths in the optical network. The path computation engine may have instructions executable by a processor having access to a storage medium that stores the instructions. Yet another disclosed aspect may include an optical network having a path computation engine as described herein.

For a more complete understanding of the present invention and its features and advantages, reference is made to the following description, taken in conjunction with the accompanying drawings, in which:
FIG. 3 is a block diagram of selected elements of one embodiment of an optical network. FIG. 2 is a block diagram of selected elements of one embodiment of an optical network control system. FIG. 3 is a block diagram of selected elements of one embodiment of a network topology. FIG. 3 is a block diagram of selected elements of one embodiment of a network topology. 6 is a flowchart of selected elements of one embodiment of a method for optical path computation based on a memory efficient matrix. 6 is a flowchart of selected elements of one embodiment of a method for optical path computation based on a memory efficient matrix. FIG. 4 is a network diagram of selected elements of one embodiment of a hierarchical guided search graph. FIG. 4 is a network diagram of selected elements of one embodiment of a hierarchical guided search status tree. 6 is a flowchart of selected elements of one embodiment of a method for light path evaluation using hierarchical guided search.

  In the following description, details are set forth as an example to facilitate discussion of the disclosed subject matter. However, it will be apparent to one skilled in the art that the disclosed embodiments are illustrative and are not exhaustive of all possible embodiments.

  As used herein, a reference sign in the form of a hyphenated form represents a particular instance of one element, and a reference sign in the form without a hyphen represents a collective element. Thus, for example, device “72-1” (not used in the figure) may represent an instance of a device class, or may be collectively represented as device “72”, any of these Things may generally be represented as device “72”.

  Returning to the figure, FIG. 1 illustrates an exemplary embodiment of an optical network 101. As shown, the optical network 101 may show a transport plane view that includes elements that carry user data and have network equipment. Accordingly, the optical network 101 may have one or more optical fibers 106 configured to carry one or more optical signals communicated by components of the optical network 101. The network elements of the optical network 101 are coupled together by a fiber 106, one or more transmitters 102, one or more multiplexers (MUX) 104, one or more amplifiers 108, one or more optical add / drop multiplexers ( An optical add / drop multiplexer (OADM) 110 and one or more receivers 112 may be included.

  The optical network 101 may comprise a point-to-point optical network with terminal nodes, a ring optical network, a mesh optical network, or any other suitable optical network or combination of optical networks. The optical fiber 106 may have a thin glass string capable of transmitting a signal over a long distance with very low loss. The optical fiber 106 may comprise any suitable type of fiber.

  The optical network 101 may include devices that are configured to transmit optical signals over the fiber 106. Information may be transmitted and received over the network 101 by modulation of one or more wavelengths of light to encode information about the wavelength. In an optical network, the wavelength of light is also called a channel. Each channel may be configured to convey a specific amount of information through the optical network 101.

  In order to increase the information transfer capability of the optical network 101, multiple signals transmitted on multiple channels may be combined into a single optical signal. The process of communicating information over multiple channels of a single optical signal is optically referred to as wavelength division multiplexing (WDM). Dense wavelength division multiplexing (DWDM) refers to multiplexing into a single fiber at a higher number (higher density), usually more than 40 wavelengths. WDM, DWDM, or other multiple wavelength transmission technologies are used in optical networks to increase the aggregate bandwidth per optical fiber. Without WDM or DWDM, the bandwidth in an optical network can be limited to a bit rate of just one wavelength. With greater bandwidth, the optical network can transmit more information. Optical network 101 may be configured to transmit different channels and amplify multi-channel signals using WDM, DWDM, or some other suitable multi-channel multiplexing technique.

  The optical network 101 may include one or more optical transmitters (Tx) 102 that are configured to transmit optical signals through the optical network 101 at specific wavelengths or channels. The transmitter 102 may include any system, device, or apparatus configured to convert electrical signals into optical signals and transmit the optical signals. For example, each transmitter 102 transmits a laser and a beam that receives an electrical signal and modulates information contained in the electrical signal into a beam of light generated by the laser at a specific wavelength and transmits the signal through the network. And a modulator configured as described above.

  Multiplexer 104 may be coupled to transmitter 102 and is any system, apparatus or device configured to combine signals transmitted at individual wavelengths by transmitter 102 into a single WDM or DWDM signal. May be.

  The amplifier 108 may amplify the multi-channel signal in the optical network 101. The amplifier 108 may be placed before or after the specific length of fiber 106. The amplifier 108 may comprise any system, device or apparatus configured to amplify the signal. For example, the amplifier 108 may include an optical repeater that amplifies the optical signal. This amplification may be performed by opto-electric or electro-optical conversion. In some embodiments, the amplifier 108 may comprise an optical fiber doped with rare earth elements. As the signal passes through the fiber, external energy is applied, exciting the atoms in the doped portion of the optical fiber and increasing the intensity of the optical signal. As an example, the amplifier 108 may include an erbium-doped fiber amplifier (EDFA). In various embodiments, other suitable amplifiers, such as semiconductor optical amplifiers (SOA), may be used.

  OADM 110 may be coupled to optical network 101 via fiber 106. The OADM 110 may include an add / drop module that may include any system, device, or apparatus configured to add and drop optical signals from the fiber 106. After passing through the OADM 110, the signal may travel directly to the destination along the fiber 106, or the signal may pass through one or more additional OADMs 110 before reaching the destination. In a particular embodiment of the optical network 110, the OADM 110 adds or drops individual or multiple wavelengths of a WDM signal carrying a data channel to be added or dropped in the optical domain, for example using a wavelength selective switch (WSS). A possible ROADM (reconfigurable OADM) may be represented.

  The optical network 101 may include one or more demultiplexers 105 at one or more destinations of the optical network 101. The demultiplexer 105 may comprise any system, device or apparatus that can operate as a demultiplexer by separating a single WDM signal into its individual channels. For example, the optical network 101 may transmit and transmit 40-channel DWDM signals. Demultiplexer 105 may split the signal, 40 channel DWDM signal, into 40 separate signals according to 40 different channels.

  The optical network 101 may have a receiver 112 coupled to the demultiplexer 105. Each receiver 112 may be configured to receive signals transmitted on a particular wavelength or channel and process the signals for the information they contain. Accordingly, the optical network 101 may have at least one receiver 112 for each channel of the network.

  An optical network, such as optical network 101, may further use a modulation scheme to convey information in an optical signal via an optical fiber. Such a modulation scheme may include PSK (phase-shift keying), FSK (frequency-shift keying), ASK (amplitude-shift keying), and QAM (quadrature amplitude modulation). In PSK, the information conveyed by the optical signal may be converted by modulating the phase of the reference signal, also known as the carrier or simply the carrier. The information may be converted by modulating the phase of the signal itself using DPSK (differential phase-shift keying). In QAM, information carried by an optical signal may be transmitted by modulating both the amplitude and phase of the carrier wave. PSK is considered part of QAM. Here, the amplitude of the carrier wave is kept constant.

  In an optical communication network such as the optical network 101, it is common to refer to a management plane, a control plane, and a transport plane (often referred to as a physical layer). A central management host (not shown) may be present in the management plane and may configure and manage components of the control plane. The management plane has ultimate control over all transport plane and control plane entities (eg, network elements). As an example, the management plane may have a central processing center (eg, a central management host) that includes one or more processing resources, data storage components, and the like. The management plane may be in electrical communication with elements of the control plane and may be in electrical communication with one or more network elements of the transport plane. The management plane may perform system-wide management functions and provide coordination between the network elements, the control plane, and the transport plane. As an example, the management plane is an EMS (element management system) that handles one or more network elements from an element perspective, an NMS (network management system) that handles many devices from a network perspective, and an OSS that handles network-wide operations. (Operational support system) may be included.

  Changes, additions or omissions may be made to the optical network 101 without departing from the scope of the present disclosure. For example, the optical network 101 may have more or fewer elements than those shown. In addition, the optical network 101 may have additional elements that are not explicitly specified, such as a dispersion compensation module. Also, as described above, illustrated as a point-to-point network, the network 101 may include any suitable network that transmits optical signals, such as a ring or mesh network.

  In operation, the optical network 101 may have various nodes and optical path connections between the nodes. As disclosed herein, an optical path calculation based on a memory efficient matrix may be performed for nodes in the optical network 101.

  Referring to FIG. 2, a block diagram of selected elements of one embodiment of a control system 200 that implements a control plane function in an optical network, such as in optical network 101 (see FIG. 1) is shown. The control plane may have functions for network intelligence and control, and the ability to establish network services including applications or modules for discovery, routing, route computation, and signaling as described in more detail. You may have supporting applications. Control plane applications executed by the control system 200 may work together to automatically establish services within the optical network. The discovery module 212 may discover local links that connect neighbors. The routing module 210 may broadcast local link information to the optical network nodes while populating the database 204. When a request for service from the optical network is received, the route calculation engine 202 may be invoked to calculate a network route using the database 204. This network path may then be provided to the signaling module 206 to establish the requested service.

  As shown in FIG. 2, the control system 200 includes a processor 208 and a storage medium 220. The storage medium 220 may store executable instructions (ie, executable code) that are executable by the processor 208 having access to the storage medium 220. The processor 208 may execute instructions that cause the control system 200 to perform the functions and operations described herein. For the purposes of this disclosure, the storage medium 220 may include a non-transitory computer readable medium that stores data and instructions for at least a period of time. Storage medium 220 may include permanent and volatile media, fixed and removable media, magnetic and semiconductor media. The storage medium 220 includes a direct access storage device (for example, a hard disk drive or a floppy (registered trademark) disk), a sequential access storage device (for example, a tape disk drive), a CD (compact disk), a RAM (random access memory), a ROM (read -Only memory), CD-ROM, DVD (digital versatile disc), EEPROM (electrically erasable programmable read-only memory), and storage media such as flash memory, non-transitory media, or various combinations thereof However, it is not limited to these. Storage medium 220 operates to store instructions, data, or both. A storage medium 220 as shown has a set or sequence of instructions that may represent an executable computer program, ie, a route calculation engine 202, a signaling module 206, a discovery module 212, and a routing module 210. As described herein, the route calculation engine 202 may represent instructions or code that, in conjunction with the signaling module 206, discovery module 212, and routing module 210, implement various algorithms according to the present disclosure.

  The control system 200 of FIG. 2 also includes a network interface 214. Network interface 214 may be any suitable system, device, or apparatus that operates to serve as an interface between processor 208 and network 230. The network interface 214 may allow the control system 200 to communicate over the network 230 using an appropriate transmission protocol or standard. In some embodiments, network interface 214 may be communicatively coupled to network storage resources via network 230. In some embodiments, the network 230 may be an embodiment of at least certain portions of the optical network 101. The network 230 may include a specific portion of the network that uses galvanic or electronic media. In particular embodiments, network 230 may comprise at least a particular portion of a public network such as the Internet. Network 230 may be implemented using hardware, software, or various combinations thereof.

  In certain embodiments, the control system 200 may be configured to interact with a person (ie, a user) and receive data regarding the optical signal transmission path. For example, the control system 200 has or is coupled to one or more input devices and output devices to achieve reception of data regarding the optical signal transmission path from the user and to output the results to the user. May be. One or more input or output devices (not shown) may include, but are not limited to, a keyboard, mouse, touchpad, microphone, display, touch screen display, audio speaker, and the like. Alternatively or additionally, the control system 200 may be configured to receive data regarding the optical signal transmission path from a device such as another computing device or network element, eg, via the network 230.

  As shown in FIG. 2, in some embodiments, the discovery module 212 may be configured to receive data regarding optical signal transmission paths in an optical network and is responsible for discovery of neighbors and links between neighbors. May be. In other words, the discovery module 212 may transmit a discovery message according to a discovery protocol and may receive data regarding the optical signal transmission path. In some embodiments, discovery module 212 may include, among other things, fiber type, fiber length, number and type of components, data rate, data modulation format, optical signal input power, number of signal carrier wavelengths (ie, channels), among others. Such as, but not limited to, channel spacing, traffic requirements, and network topology.

  As shown in FIG. 2, the routing module 210 may be responsible for propagating link connectivity information to various nodes in an optical network such as the optical network 101. In certain embodiments, the routing module 210 may populate the database 204 with resource information to support traffic engineering, which may include link bandwidth availability. Accordingly, the database 204 may be populated by the routing module 210 with information useful for determining the network topology of the optical network.

  The route calculation engine 202 may be configured to use information provided to the database 204 by the routing module 210 to determine the transmission characteristics of the optical signal transmission route. The transmission characteristics of the optical signal transmission path include chromatic dispersion (CD), nonlinear (NL) effect, polarization mode dispersion (PMD), and polarization dependent loss (PDL). Such polarization effects as well as insight into how transmission degradation factors such as amplified spontaneous emission (ASE) can affect the optical signal in the optical signal transmission path may be provided. In order to determine the transmission characteristics of the optical signal transmission path, the path calculation engine 202 may consider the interaction between transmission degradation factors. In various embodiments, the route calculation engine 202 may generate values for specific transmission degradation factors. The route calculation engine 202 may further store data describing the optical signal transmission route in the database 204.

  In FIG. 2, the signaling module 206 may provide functions related to setting, changing, and tearing down an end-to-end service for an optical network such as the optical network 101. For example, when an ingress node in an optical network receives a service request, control system 100 uses signaling module 206 to network from path computation engine 202 that can be optimized according to different criteria such as bandwidth, cost, etc. A route may be requested. Once the desired network path is identified, the signaling module 206 may then communicate with individual nodes along the network path to establish the requested network service. In different embodiments, the signaling module 206 may use a signaling protocol to propagate subsequent communications to and from the node along the network path.

  In operation of the control system 200, the optical path calculation feature may include end-to-end reachable path calculation. As described above, a direct reachable path represents a path between a source node and a destination node in an optical network where an optical signal is transmitted and received purely through an optical component between the source node and the destination node. May be. Such direct reachable paths include, for example, a source node and a destination node that include electrical regeneration of an optical signal using an OEO regenerator, referred to herein simply as a “regenerator”, before reaching the destination. It may be in contrast to the indirectly reachable route between The indirectly reachable path may have a plurality of regenerators. Thus, the end-to-end reachable path may have a path from the source node to the first regenerator node, to at least one second regenerator node, and ultimately to the destination node. . The route calculation engine 202 is configured to find an end-to-end reachable route that integrates a minimal or specifically specified number of regenerators while meeting other route constraints such as latency and cost. Also good.

  The route calculation engine 202 may be further configured to perform graph transformation to determine end-to-end reachable route calculation. The graph transformation can include adding a virtual link to the physical topology initially determined from the physical components of the optical network. A virtual link may represent a link connecting two nodes so that the two nodes are optically reachable without regenerator intervention. After all the virtual links that optically reach the node pairs are added to the graph topology, the original topology may be converted to a reachability graph. Thereafter, minimum hop routing may be performed to obtain an end-to-end reachable path that requires a minimum number of regenerators. To perform such functions, a computationally expensive route algorithm is used by the route computation engine 202 to obtain the desired number and type of reachable routes. However, configuring the path computation engine 202 to perform end-to-end reachable path computation based on such graph transformation involves the use of extensive graph theory and routing algorithms. This is complicated and burdensome to handle.

  Further, the path calculation engine 202 may be configured to perform reachability matrix type optical path calculation based on matrix operations rather than relying on graph transformation. Accordingly, the path calculation engine 202 may be configured to use the reachability matrix to represent the corresponding reachability graph and perform the optical path calculation based on the matrix operation, and thus complex graph transformations and Routing algorithms can be avoided. By using optical path computation based on the reachability matrix, the path computation engine 202 can be configured with low optical engineering complexity. Furthermore, the route calculation engine 202 may aggregate the optical route calculation functions of various parts of the optical network 101. Further, the route calculation engine 202 may provide an abstracted optical network view to the control system 200 to enable SDN (software-defined network) in the optical network 101. Although the control system 200 and the path computation engine 202 are shown as a single element in FIG. 2, the optical path computation performed by the path computation engine 202 is modularized and implemented, scalable and spans multiple devices (not shown). It will be appreciated that it may be deployed in a parallel manner to support path computation in an optical network of varying size or node complexity.

  As described in further detail herein, during operation, the control system 200 may be used for optical path computation based on a memory efficient matrix. Specifically, the path calculation engine 202 may be used to perform an optical path calculation based on a matrix operation using a reachability matrix. Furthermore, the path computation engine 202 is based on a memory efficient matrix with a single matrix M that can hold all information or equivalent information when stored in a series of reachability matrices RM ^ i. Optical path calculation may be performed. In this method, the optical path calculation based on the memory efficient matrix disclosed herein is a series of reachability matrices RM ^ i, i = 1,. . . , The amount of computation resources per R (eg, by the route computation engine 202) can be reduced. Where i is the minimum number of hops indicated by the individual reachability matrix RM ^ i, and R is the upper limit of i, such as the total number of nodes in a given network topology. A computational resource may include an amount of memory or computational efficiency that may be a determinant of computational feasibility. In particular, in a large network having N nodes, such as thousands of nodes, where N is relatively large, optical path computation based on a memory efficient matrix as disclosed herein is computationally In a manageable manner, it allows the computation of the full series reachability matrix RM ^ i or any desired one of the reachability matrices RM ^ i at a desired time, especially relevant for optical network provisioning For real-time applications, such optical path calculation is made feasible or economically feasible.

Specifically, the element values of the matrix M are, for example, the number of all optical paths that can be concatenated to form all the optical paths from a desired source node to a desired destination node in the optical network 101 (ie, _{M ij} indicating hop). In a particular embodiment, m _ij has a value of 1, plus the minimum number of regenerators that connect node i to node j when node i and node j are reachable using regenerators. May be. When node i and node j are not reachable using any number of regenerators, m _ij may have a value of zero (0). As described below, in various embodiments, m _ij may be 0 or 1 when i = j. Thus, the matrix M is calculated using so-called “in-place” memory consumption, where the previous value (or previous iteration) of M can be overwritten with the current value (or current iteration) of M without information loss. obtain. A first algorithm for calculating M that is computationally efficient (at least O (N ^ 3)) is described in more detail with respect to FIG.

［表１］ネットワークトポロジ３００の全ての到達可能性マトリックス（ＲＭ） Referring to FIG. 3, a block diagram of selected elements of an embodiment of a network topology 300 illustrating an exemplary embodiment of optical path computation based on a memory efficient matrix as disclosed herein. Is shown. As shown, the network topology 300 includes nodes A, B, C, and D, and a specific directional optical path 302 exists between these nodes. In the network topology 300, the optical path 302-1 enables optical communication from the node B to the node A. In the network topology 300, the optical path 302-2 enables optical communication from the node A to the node C. In the network topology 300, the optical path 302-3 enables optical communication from the node C to the node D. In the network topology 300, the optical path 302-4 enables optical communication from the node D to the node A. In the network topology 300, the optical path 302-5 enables optical communication from the node C to the node B. Accordingly, the reachability matrix (RM) of the network topology 300 may be given in Table 1, as disclosed in US patent application Ser. No. 14 / 169,980.

Table 1 All reachability matrices (RMs) of network topology 300

  In Table 1 and in the following table showing the matrix, the rows represent source nodes and the columns represent destination nodes. Thus, each value of 1 for different nodes in the reachability matrix of Table 1 represents the directional light path 302 of FIG. As an optional practice, the identification value in the reachability matrix of Table 1 is 1 for connections to the same node, but may be 0 in other embodiments.

［表２］ネットワークトポロジ３００の到達可能性マトリックス（ＲＭ）に基づくマトリックスＭの開始バージョン One exemplary embodiment of a first algorithm for optical path computation based on memory efficient matrix for network topology 300 for computing matrix M is described in further detail below. The first algorithm is computationally efficient (at least O (N ^ 3)) and may be based on the transitive closure Floyd-Warshall algorithm. The first algorithm may start with the reachability matrix of Table 1 for network topology 300. In the first algorithm, the reachability matrix of Table 1 may be modified to yield a starting version of Matrix M as given in Table 2.

TABLE 2 Starting version of matrix M based on reachability matrix (RM) of network topology 300

  In Table 2, the identification value from the reachability matrix of Table 1 is set to 0 for connections to the same node. This is an arbitrary practice of identification values. Also in Table 2, a value of 0 from the reachability matrix of Table 1 is given the value X. In some embodiments, the value X may be selected to be infinite (∞) for computational purposes. In a given embodiment, the value X may be selected to be greater than any other numerical value for computational purposes. In certain embodiments, the value X may be selected to be the maximum range of variables for computational purposes. In certain embodiments, the value X may be selected to be greater than the number of nodes in the network topology where the optical path calculation is being performed, such as greater than 4 for the network topology 300.

［表３］マトリックスＭを計算するための第１のアルゴリズムの擬似コード In the first algorithm, matrix M represents the minimum number of all optical paths that the matrix elements in matrix M can be concatenated to create an end-to-end all-optical connection between two nodes for each individual matrix element. So that it is finally calculated. Starting from the matrix M in Table 2, the matrix M can be calculated in-place in successive steps or iterations to minimize memory consumption for calculating the matrix M. In some embodiments, the continuous step may be repeated over n iterations. In some embodiments, the continuous step may end after fewer than n iterations, eg, when the matrix M converges before reaching n iterations. n is the number of nodes in the network topology for which the matrix M is calculated, k = 1,. . . , N, for each successive step k, the calculation of the matrix M in the first algorithm can be shown by the pseudo code given in Table 3.

[Table 3] Pseudo code of first algorithm for calculating matrix M

［表４］ｋ＝１について第１のアルゴリズムでのマトリックスＭの第１の反復 As is apparent in the pseudo code shown in Table 3, for each value of k repeated in the first algorithm, table k and column k remain unchanged from the previous matrix M. Based on the pseudo code in Table 3, and based on the starting version of the matrix M in Table 3, the first step of calculating the final matrix M according to the first algorithm for k = 1 is shown in Table 4.

TABLE 4 First iteration of matrix M with first algorithm for k = 1

  In Table 4, when k = 1, row A and column A remain the same as in Table 3 in the first iteration of the first algorithm. In Table 4, the elements in row B and column C change to 2, indicating that it is 2 hops to reach node C from node B in network topology 300 with the first algorithm. In Table 4, the elements in row D, column C change to 2, indicating that it is 2 hops to reach node C from node D in network topology 300 with the first algorithm.

［表５］ｋ＝２について第１のアルゴリズムでのマトリックスＭの第２の反復 Based on the pseudo code in Table 3, and based on the first iteration of the matrix M in Table 4, the second step of calculating the final matrix M according to the first algorithm for k = 2 is shown in Table 5.

TABLE 5 Second iteration of matrix M with first algorithm for k = 2

  In Table 5, when k = 2, row B and column B remain the same as in Table 4 in the second iteration of the first algorithm. In Table 5, the element in row C, column A changes to 2, indicating that it is 2 hops to reach node A from node C in network topology 300 with the first algorithm.

［表６］ｋ＝３について第１のアルゴリズムでのマトリックスＭの第３の反復 Based on the pseudo code in Table 3, and based on the second iteration of the matrix M in Table 5, the third step of calculating the final matrix M according to the first algorithm for k = 3 is shown in Table 6.

Table 6 Third iteration of matrix M with first algorithm for k = 3

  In Table 6, when k = 3, row C and column C remain unchanged from Table 5 in the third iteration of the first algorithm. In Table 6, the elements in row A and column B change to 2, indicating that it is 2 hops to reach node B from node A in network topology 300 with the first algorithm. In Table 6, the elements in row A, column D change to 2, indicating that it is 2 hops to reach node A from node D in network topology 300 with the first algorithm. In Table 6, the element in row B, column D changes to 3, indicating that it is 3 hops to reach node D from node B in network topology 300 with the first algorithm. In Table 6, the elements in row D, column B change to 3, indicating that it is 3 hops to reach node B from node D in network topology 300 with the first algorithm.

［表７］ｋ＝４について第１のアルゴリズムでのマトリックスＭの第４の反復 Based on the pseudo code in Table 3, based on the third iteration of the matrix M in Table 6, the fourth step of calculating the final matrix M according to the first algorithm for k = 4 is shown in Table 7.

[Table 7] Fourth iteration of matrix M with first algorithm for k = 4

  In Table 7, when k = 4, row D and column D remain the same as in Table 6 in the fourth iteration of the first algorithm. In Table 7, no change from Table 6 occurs based on the pseudo code in Table 3. As described above in the first algorithm, the matrix M holds values indicating the minimum number of hops representing each individual total optical path for each individual node pair in a given network topology. When each non-zero value (or each non-identifying value) in the matrix M is subtracted by 1, the resulting value gives the number of regenerators to reach each individual node pair by all optical paths. Can be represented.

［表８Ａ］マトリックスＭからマトリックスＲＭ＾ａを計算するアルゴリズムの擬似コード Once the matrix M is calculated in the final convergence state, the matrix M can be used to generate the desired reachability matrix RM ^ i. The algorithm for obtaining the reachability matrix RM ^ a from the matrix M is shown as pseudo code in Table 8A. In Table 8A, element rm _ij is an element in reachability matrix RM ^ a, a is the desired number of hops, and element m _ij is the corresponding element in matrix M. In the exemplary algorithm of Table 8A, the elements of RM ^ a are defined to indicate reachability between two nodes in terms of the number of hops or less.

[Table 8A] Pseudo code of algorithm for calculating matrix RM ^ a from matrix M

［表８Ｂ］マトリックスＭからマトリックスＲＭ＾ａを計算するアルゴリズムの擬似コード Table 8B shows another alternative algorithm for obtaining RM ^ a, where the elements are defined to indicate reachability in exactly hop counts.

[Table 8B] Pseudo code of algorithm for calculating matrix RM ^ a from matrix M

  Thus, once the matrix M is computed, any reachability matrix RM ^ a can be generated with relatively few computational resources, including memory consumption, based on the algorithm of Table 8A or 8B.

［表９］表８Ａの擬似コードを用いて表６のマトリックスＭから計算された到達可能性マトリックスＲＭ＾１ A first exemplary calculation of the algorithm of Table 8A for a = 1 using the matrix M calculated above for network topology 300 with the first algorithm from Table 6, for example, is given in Table 9. It should be noted that the identification value in Table 9 is 1 due to the code conversion used in the algorithm of Table 8A.

[Table 9] Reachability matrix RM ^ 1 calculated from matrix M in Table 6 using the pseudo code in Table 8A

［表１０］表８Ａの擬似コードを用いて表６のマトリックスＭから計算された到達可能性マトリックスＲＭ＾２ A second exemplary calculation of the algorithm of Table 8A for a = 2, for example using matrix M calculated above for network topology 300 with the second algorithm from Table 6, is given in Table 10. It should be noted that the identification value in Table 10 is 1 due to the code conversion used in the algorithm of Table 8A.

[Table 10] Reachability matrix RM ^ 2 calculated from matrix M in Table 6 using the pseudo code in Table 8A

［表１１］マトリックスＭを計算するための第２のアルゴリズムの擬似コード A second algorithm for calculating each continuous matrix M (a) starting from RM 1 in Table 1 for the network topology 300 is illustrated by the pseudo code in Table 11. In the second algorithm, for each successive value of a, M (a) is multiplied using a Boolean matrix multiplication by the reachability matrix RM ^ 1.

[Table 11] Pseudo code of second algorithm for calculating matrix M

  In the second algorithm, when the convergence of M is detected, the second algorithm may end early. The second algorithm may approach O (N ^ 3) as a increases, and may be performed in-place by overwriting elements at each successive iteration.

  As disclosed, different methods may be used to calculate the matrix M.

  In the first embodiment of calculating the matrix M, each reachability matrix RM ^ i is pre-computed for all i or until the reachability matrix converges (or no longer changes with self-growth). May be. Next, the information in all the matrices RM ^ i may be encoded into the matrix M. In the first embodiment for calculating the matrix M, all individual reachability matrices RM ^ i may coexist in the memory.

  In the second embodiment in which the matrix M is calculated using the first algorithm or the second algorithm described above, the initial reachability matrix RM ^ 1 may be used as a starting point. An in-place calculation may then be performed on the continuous matrix starting from RM ^ 1 to obtain the final matrix M by calculating the transitive closure. The final matrix M may have information from all reachability matrices RM ^ i. In the second embodiment for calculating the matrix M, the calculation speed and memory consumption are reduced, and the required calculation resources can be reduced.

  Referring to FIG. 4, a block diagram of selected elements of one embodiment of a network topology 400 illustrating an exemplary embodiment of an optical path calculation based on a memory efficient matrix as disclosed herein. Is shown. As shown, the network topology 400 has a source node S and a destination node D, and a plurality of other network nodes shown as circles. The position of the network node in the network topology 400 indicates the relative position of the network node, and the network topology is not shown to scale. As described above for network topology 300, matrix M is calculated for network topology 400 based on the physical network topology of the optical paths between nodes in network topology 400, which is omitted in FIG. 4 for clarity of explanation. Also good. Matrix M may allow determining the number of regenerators used to connect any node pair in network topology 400. Thus, the matrix M may be used to find possible regenerator positions for a desired optical path between the source node S and the destination node D in the network topology 400.

  Initially, matrix M may be used to generate reachability matrices RM ^ 1 and RM ^ 2 of network topology 400 as described above with respect to FIG. Next, a first set 402 of nodes in network topology 400 may be identified from reachability matrices RM ^ 1 and RM ^ 2 obtained from matrix M. Here, the first set 402 includes nodes that are reachable in 1 hop from the destination node D and in 2 hops from the source node S. Next, a second set 404 of nodes in the network topology 400 may be identified from the reachability matrices RM ^ 1 and RM ^ 2 obtained from the matrix M. Here, the second set 404 includes nodes that are reachable in one hop from the first set 402 and in one hop from the source node S.

  After the first set 402 and the second set 404 are identified, the end-to-end connection between the source node S and the destination node D is identified using the second set 404 and the first set 402. May be. The second set 404 may represent possible first hop positions from the source node S. On the other hand, the first set 402 may represent possible first hop positions from the destination node D. Next, a first hop location from the second set 404 to the first set 402 may be identified. In this way, possible end-to-end connections between the source node S and the destination node D may be identified. A possible end-to-end connection may represent various possible connections between a source node S and a destination node D that can be evaluated using various criteria to select a desired connection. It should be noted that the number of iterations of the procedure for selecting a set of nodes may be bounded by the values in matrix M for the source node S and destination node D pairs.

  Referring to FIG. 5, a flowchart of selected elements of one embodiment of a method 500 for optical path computation based on a memory efficient matrix is shown. The method 500 may be implemented for optical path calculation using the matrix M by the path calculation engine 202 in an exemplary embodiment as disclosed herein. It should be noted that the particular operations described in method 500 may be optional or rearranged in different embodiments.

  Method 500 may begin by calculating a reachability matrix RM ^ 1 for each node pair in the optical network (operation 502). Based on the reachability matrix RM ^ 1, for each node pair, an in-place algorithm is used to calculate the minimum number of all optical paths between individual node pairs in the matrix M (operation 504). Act 504 may include applying a transitive closure algorithm to perform an iterative in-place calculation for successive iterations of the matrix M. On the other hand, iterative in-place computation may be performed for a maximum number of iterations corresponding to the number of nodes in the optical network. Operation 504 may be performed using the first algorithm or the second algorithm described above with respect to FIG. Based on the minimum number of total optical paths between each node pair in the matrix M, the minimum number of regenerators for each node pair is determined (operation 506). The minimum number of regenerators determined in operation 506 may be the non-zero values of matrix M minus 1 from the individual values in matrix M. A source-destination pair may be selected having a value in matrix M greater than 1 (operation 508). A possible optical path between the source node and the destination node is determined (operation 510), and the possible optical path has a minimum number of regenerators for the source-destination pair. Possible optical paths between the source node and the destination node may be evaluated to select a desired optical path (operation 512).

  Referring to FIG. 6, a flowchart of selected elements of one embodiment of a method 600 for optical path computation based on a memory efficient matrix is shown. The method 600 may be implemented for optical path calculation using the matrix M by the path calculation engine 202 in an exemplary embodiment as disclosed herein. Method 600 may represent one embodiment of operation 510 in method 500 of FIG. It should be noted that the particular operations described in method 600 may be arbitrary or rearranged in different embodiments.

  Method 600 begins after operation 508 of method 500 by making G the minimum number of source-destination pair regenerators in matrix M (operation 602) and H = 1 (operation 602). May be. The method 600 may then perform an iterative procedure at operations 604, 606 and 608. Here, a reference to “next set of nodes” is used to specify an iterative instance of a set of nodes in an iterative procedure. The next set of nodes in the optical network is determined (operation 604). The next set of nodes is reachable using H hops from the destination node and G hops from the source node. Next, G may be decremented (operation 606) and H may be incremented (operation 608). Next, a determination may be made as to whether G = 0 (operation 608). When G ≠ 0, the result of operation 608 is NO and method 600 may loop back to operation 604. When G = 0, the result of operation 608 is YES, and possible optical paths between the source node and the destination node may be generated based on the set of nodes (operation 610). Possible optical paths include the minimum number of regenerators for source-destination pairs. After operation 610, method 600 may proceed to operation 512 of method 500.

  As described above, when performing optical path computation based on matrix operations using reachability matrices, for example, the amount of memory consumed by the path computation engine 202 to assess the desirability or economic feasibility of the optical path Can be a limiting factor in performing such calculations. The optical path may be evaluated to determine the optimal regenerator position solution, as described above with respect to FIG. Thus, the method described above for the in-place computation of the matrix M is a computational solution for performing optical path computations even in large networks having N nodes, where N is a relatively large value, such as thousands of nodes. Easy to handle. As described above with respect to FIGS. 3-6, possible optical paths may represent a hierarchical organization of regenerator stages, and possible regeneration identified with first set 402 and second set 404 of FIG. It may be identified along with the vessel position.

  As described in more detail below, a hierarchical guided search may be performed to select a specific light path from the possible light paths based on the identified possible light paths and regenerator stages. Hierarchical guided search (HGS) includes identified regenerator stages between a source node and a destination node together with an optical path group (OPG) connecting the nodes. ) A graph may be used. As described, the hierarchical guided search may utilize possible regenerator location information as well as minimum cost information of the optical path between nodes.

  An optical path group may collectively represent one or more all-optical paths (OP) in a single direction between a given pair of nodes. Thus, each matrix element in matrix M may represent a single light path group. If the matrix elements of M are equal to zero, the corresponding optical path group represents an empty set of optical paths. Each optical path may have various series of physical optical links and optical nodes. The particular route that the optical path through the network follows may be different. In some applications where network protection with a certain level of redundancy is desired, a pair of optical paths featuring a specific level of disjointness (or more generally, n-fold optical paths or End-to-end connection) may be used. As used herein, “disjointness” refers to having exclusive access to (or not sharing) a particular optical resource in the network. For example, within an optical path group, a node-disjoint optical path may only pass through different optical nodes (or no shared nodes) except for the source and destination nodes. ). Link-disjoint optical paths may only pass through different optical links (or may not pass through any shared optical links). A particular separation optical path may be defined as both node separation and link separation.

  With two end-to-end connections that are node-separated, the main feature of interest in path computation is the end-to-end that does not share any regenerator node, even if the source and destination nodes of the end-to-end connection can be supplied. You may have a connection. A second feature of interest in path computation may be that each of the optical paths included in the end-to-end connection is also a node separation. With two end-to-end connections that are link-separated, the optical path set at each connection is link-separated from each other.

  Optical path groups with different source and destination nodes are more likely to be node separation or link separation, but the isolation may not be guaranteed by different source or destination nodes. Thus, regenerator node isolation of end-to-end connections may be required rather than sufficient conditions for end-to-end connections that are node or link isolation. It should be noted that in various embodiments, other types of separability may be defined and used as constraints in optical path calculations such as links that do not provide a common route.

  Next, the hierarchical guided search proceeds using a hierarchical guided search (HGS) state tree. The HGS state tree may allow hierarchical selection. In hierarchical selection, after a possible regenerator node is identified, an optical path group that includes multiple optical paths with the same source and destination nodes may be evaluated and selected based on minimum cost information. When an optical path group is selected for each separation path, an optical path from within each optical path group may be selected. During this process, the removal of possible solutions can further improve computational ease by reducing the search space early in the search process. For example, such possible options may be deleted from the solution space as soon as a particular light path or group of light paths is found not separated. In certain embodiments, the A * algorithm may be used to search or evaluate possible light paths.

  As described above, separability may represent an example of policy constraints used in the selection of a particular light path from possible or available light paths. Connection latency, distance, and power consumption are examples of economic constraints that are also referred to as cost metrics. Economic constraints may be evaluated, minimized and enforced during a search using a cost function. Policy constraints may be enforced by deleting certain possible solutions.

  Referring to FIG. 7A, selected elements of one embodiment of the HGS graph 700 are shown. In certain embodiments, the HGS graph 700 may represent one embodiment of the network topology 400 shown in FIG. It should be noted that the HGS graph 700 is an exemplary embodiment shown for illustrative purposes, and other embodiments of the HGS graph may have fewer or more elements and information.

［表１２］ＨＧＳグラフ７００の宛先ノードＤへの最小コストメトリック In FIG. 7A, the HGS graph 700 shows an optical path group 704 between the source node S and the destination node D. Optical path group 704 is arranged hierarchically with respect to regenerator stage 1 (RS ₁ ) having intermediate nodes B and C and regenerator stage 2 (RS ₂ ) having intermediate nodes F and G. For example, RS ₁ may correspond to the second set 404 of FIG. 4, while RS ₂ may correspond to the first set 402 of FIG. Each optical path group 704 in the HGS graph 700 is annotated with optical path information indicating the number of optical paths and the cost metric for each optical path. As used herein, a cost metric can be a latency, distance, hardware cost, power consumption, excess bandwidth from a desired minimum bandwidth, excess light penalty tolerance, or a different combination thereof. Economic constraints may be indicated. The cost metric is used herein as an integer metric of the relative cost of the optical paths for clarity of explanation. It should be noted that in different embodiments, a finer cost metric such as a real value indicating the actual monetary cost may be used. Specifically, the optical path group 704-1 has two all optical paths between the source node S and the node B having cost metrics 2 and 3, respectively. The optical path group 704-2 has three all optical paths between the source node S and the node C having cost metrics 3, 5 and 6, respectively. Optical path group 704-3 has two total optical paths between Node B and Node F with cost metrics 2 and 4, respectively. The optical path group 704-4 has one all-optical path between the source node B and the node G each having the cost metric 1. Optical path group 704-6 has two total optical paths between node F and destination node D with cost metrics 4 and 7, respectively. Optical path group 704-7 has two total optical paths between node G and destination node D with cost metrics 2 and 9, respectively. Based on the cost metric information in the HGS graph 700, the minimum cost metric from each node to the destination node D is given in Table 12 and shown in the diamond next to each individual node in FIG. 7A. Here, the destination node D itself is omitted.

[Table 12] Minimum cost metric to destination node D of HGS graph 700

  Referring to FIG. 7B, selected elements of one embodiment of the HGS graph state tree 701 are shown. In a given embodiment, the HGS state tree 701 may be based on the HGS graph 700 shown in FIG. 7A. It should be noted that the HGS state tree 701 is an exemplary embodiment shown for illustrative purposes, and other embodiments of the HGS state tree may have fewer or more elements and information.

  In the HGS state tree 701, the hierarchical search and determination process determines the lowest cost optical path from the source node S to the destination node D based on the HGS graph 700. Thus, the leaves of the HGS state tree 701 represent the light path group 704, while the lines in the HGS state tree 701 represent the selection of the continuous light path group 704. Here, a solid line indicates a selected optical path group, and a broken line indicates an unselected optical path group.

In the HGS state tree 701, starting from the source node S, the first decision is the cost metric information available to the optical path group 704-1 to the node B or the optical path group 704-2 to the node C. It may be done to select based on. The remaining cost metric from both nodes B and C (see also Table 12) is 3, and the overall minimum cost estimate from source node S to destination node D is 5. Thus, from the source node S, the first determination may be made to select the lowest cost all-optical path to RS ₁ . As is apparent from the HGS graph 700, the optical path group 704-1 has an optical path having cost metrics 2 and 3, while the optical path group 704-2 has an optical path having cost metrics 3, 5, and 6. Have a route. Therefore, OP (2) from optical path group 704-1 is selected as RS ₁ by the first decision. As a result of the first determination, the optical path group 704-2 is not selected, and the optical path group 704-5 is also deleted in the first determination.

Next, from the optical path group 704-1 OP (2), in the HGS state tree 701, to select from the optical path group 704-3 from the node B to the node F, or to the node G A second decision may be made to select group 704-4. The remaining cost metric from node F is 4, the remaining cost metric from node G is 2, and node G is preferred. Further, in the optical path group 704-4, the lowest cost optical path in RS ₂ is OP (1), and the node G is preferable. Thus, from Node B, a second decision may be made to select the lowest cost all-optical path to RS _2, where OP (1) from optical path group 704-4 is the _first to RS ₁ . Selected by the decision. As a result of the second determination, the optical path group 704-3 is not selected, and the optical path group 704-6 is also deleted in the second determination.

Finally, a third decision is made to select the optical path group 704-7 from node G to destination node D. Here, OP (2) is selected as the lowest cost all-optical path. Therefore, from a Node B, a second determination is performed, selects all optical paths of the lowest cost to the RS _2, the optical path group 704-4 OP (1) is in the third decision to RS ₂ Selected. The third decision results in an overall cost metric 5 from the source node S to the destination node D. This confirms that the light path with the lowest cost metric is selected.

  The above procedure for decisions using the HGS state tree 701 is presented for clarity of explanation and how the information in the HGS graph 700 is utilized to obtain a single lowest cost metric optical path. Showed. This does not introduce the issue of separability between light paths. When an additional optical path between the source node S and the destination node D is desired, the above procedure deletes the previously selected optical path and the previously selected regenerator node to obtain the additional optical path. May be repeated for. It should be noted that node deletion may be temporary, eg, during a given iteration of processing information in the HGS graph 700, and previously deleted nodes may be reconsidered in later attempts. May be.

  However, when using the HGS state tree 701, consideration of separated optical paths may be introduced when selecting an optical path or optical path group. As mentioned above, the optical paths in different optical path groups may not be completely separated due to the physical network topology. In particular, when selecting a plurality of optical paths such as an N-tuple separation optical path between the source node S and the destination node D, all the optical paths are selected when the OPG leaves of the HGS state tree 701 are cut off. It can be an effective mechanism to improve the efficiency of hierarchical guided searches compared to conventional approaches where separability is evaluated later. N-tuple separation optical paths are desirable in the real world provision of various implementations of optical networks. For example, when high network availability or reliability is desired, operational and protection paths that are two-tuple separated are desirable.

  In the HGS state tree 701, separability may be considered when selecting between successive optical paths at each leaf and based on the remaining cost metrics to the destination node. In this way, the evaluation of separability is made more efficient due to the limited number of light paths considered at a given time. Knowing that the two optical paths are non-separated, the selection based on the cost metric may be made among the remaining optical paths that may be separated. In certain embodiments, additional criteria such as maximum resolution may be applied to procedures using, for example, the HGS search tree 701. In this method, the hierarchical guided search using the HGS graph 700 and the HGS state tree 701 may obtain the lowest cost optical path for a desired separation degree of the N-tuple separated optical path.

  Referring to FIG. 8, a flowchart of selected elements of one embodiment of a method 800 for optical path evaluation using hierarchical guided search is shown. The method 800 may be implemented for optical path calculation by the path calculation engine 202 in an exemplary embodiment as disclosed herein. In certain embodiments, method 800 may be an embodiment of method 512 of method 500 (see FIG. 5). The method 800 may be performed using the HGS graph 700 (see FIG. 7) in various embodiments. It should be noted that the particular operations described in method 800 may be arbitrary or rearranged in different embodiments.

  Method 800 may begin by generating an associated node based on matrix M according to a set of all optical paths and a regenerator stage between a source node and a destination node (operation 802). Next, path calculation information may be generated for the set of all optical paths (operation 804). The route calculation information may be a cost metric for each optical route. Based on the route calculation information, node cost information may be calculated for each node up to the destination node (operation 806). The node cost information may include a minimum cost metric for each node up to the destination node. Next, an HGS graph may be generated (operation 808). The HGS graph may include a set of all optical paths, an optical path group having optical paths between common nodes, path cost information, and nodes associated with the node cost information. In a particular example, the optical path may be N-tuple separation. Based on the HGS graph, the lowest cost optical path may be determined between the source node and the destination node (operation 810). The HGS state tree may be used to select the lowest cost optical path in the process of removing unselected nodes and optical paths from consideration at an early stage of processing to minimize the search space for the process. A plurality of lowest cost optical paths may be determined. At least some of the plurality of lowest cost light paths may be separated light paths.

  As disclosed herein, the matrix M showing the minimum number of all optical paths between a pair of nodes may be generated using an algorithm for transitive closure in one embodiment. In various embodiments, different algorithms and methods may be used to generate the matrix M. Once a convergence matrix M that reaches transitive closure is generated, any corresponding reachability matrix RM ^ a for any value a may be obtained from the matrix M in a computationally efficient manner. The matrix M may be used to determine a group of possible regenerator arrangements and to obtain an end-to-end optical path by selecting a desired series of regenerators.

  As disclosed herein, the matrix M is used to determine a group of possible regenerator arrangements and to obtain a possible end-to-end optical path by selecting a desired series of regenerators. It is done. A hierarchical guided search may then be used to efficiently select the desired N-tuple separated light path from the possible light paths. Hierarchical guided search may use a search graph and a search tree to guide the search and to delete candidate nodes and light paths early in the search process.

  The above disclosed subject matter is to be considered illustrative and not restrictive. Also, the appended claims are intended to cover all modifications, extensions and other embodiments that fall within the true spirit and scope of this disclosure. Thus, to the maximum extent permitted by law, the scope of the present disclosure should be determined by the broadest acceptable interpretation of the claims and their equivalents, and is limited or limited by the foregoing detailed description. Should not.

[Reference to related applications]
This application claims priority from US Provisional Application No. 61 / 978,016, filed April 10, 2014, and named “MEMORY-EFFICIENT MATRIX-BASED OPTICAL PATH COMPUTATION”. This application claims priority from US Provisional Application No. 61 / 977,999, filed April 10, 2014, with the name “N-TUPLE DISJOINT OPTICAL PATH COMPUTATION”.

200 Control System 202 Path Calculation Engine 204 Database 206 Signaling Module 208 Processor 210 Routing Module 212 Discovery Module 214 Network Interface 220 Storage Medium 230 Network

Claims (20)

A method for evaluating an optical path in an optical network, the method comprising:
Generating a set of all optical paths between a source node and a destination node based on a matrix M having all optical path reachability information of nodes in an optical network, the all optical paths comprising: Having a minimum number of regenerators between a source node and the destination node;
Generating path cost information for the set of all optical paths, wherein the path cost information comprises cost metric information for the set of all optical paths;
Calculating node cost information to the destination node for each node associated with the all-optical path based on the path cost information;
Generating a hierarchical guided search graph having nodes associated with the set of all optical paths, an optical path group having optical paths between common nodes, the path cost information, and the node cost information;
Determining a lowest cost optical path between the source node and the destination node based on the hierarchical guidance search graph;
Having a method.   The method of claim 1, wherein the cost metric information indicates at least one characteristic of an optical path selected from latency, distance, hardware cost, power consumption, excess bandwidth, and excess light penalty tolerance. . Determining the lowest cost optical path between the source node and the destination node;
Starting from the source node in the hierarchical guidance search graph, each continuous from each node toward the destination node in the hierarchical guidance search graph based on the route cost information and the node cost information Evaluating an optical path group to a regenerator stage that includes selecting a next optical path to the next regenerator stage,
The method of claim 1, further comprising: Deleting an unselected optical path group that has not been selected from each node from further considerations, including removing an unselected node from further considerations depending on the unselected optical path group , Steps,
The method of claim 3 further comprising: Evaluating the optical path group based on the path cost information, the node cost information, and separability between selected optical paths;
Selecting the next light path to be separated from a previously selected light path;
The method of claim 3 further comprising: Determining a plurality of lowest cost optical paths between the source node and the destination node, including the lowest cost optical path;
The method of claim 3 further comprising:   The method of claim 6, wherein the plurality of lowest cost optical paths are separation paths. A path calculation engine for evaluation of an optical path in an optical network, the path calculation engine comprising the instructions executable by a processor having access to a storage medium storing instructions, the instructions comprising: In the processor,
Generating a set of all optical paths between a source node and a destination node based on a matrix M having all optical path reachability information in an optical network, wherein the all optical paths are the source node and the destination Have a minimum number of regenerators between nodes,
Generating path cost information for the set of all optical paths, the path cost information comprising cost metric information for the set of all optical paths;
Based on the path cost information, calculate node cost information to the destination node of each node related to the all-optical path,
Generating a set of all optical paths, an optical path group having optical paths between common nodes, the path cost information, and a hierarchical guidance search graph having the node cost information;
Determining a lowest cost optical path between the source node and the destination node based on the hierarchical guidance search graph;
Let the
Route calculation engine.   9. The path of claim 8, wherein the cost metric information indicates at least one characteristic of an optical path selected from latency, distance, hardware cost, power consumption, excess bandwidth, and excess light penalty tolerance. Calculation engine. The instruction to determine the lowest cost optical path between the source node and the destination node is:
Starting from the source node in the hierarchical guidance search graph, each continuous from each node toward the destination node in the hierarchical guidance search graph based on the route cost information and the node cost information An instruction that evaluates an optical path group to a regenerator stage that includes an instruction to select a next optical path to the next regenerator stage;
The route calculation engine according to claim 8, further comprising: An instruction to delete an unselected optical path group that has not been selected from each node from further consideration, including an instruction to delete an unselected node from further consideration depending on the unselected optical path group;
The route calculation engine according to claim 10, further comprising: Instructions for evaluating the optical path group based on the path cost information, the node cost information, and separability between selected optical paths;
An instruction to select the next optical path to be separated from a previously selected optical path;
The method of claim 10, further comprising: Instructions for determining a plurality of lowest cost optical paths between the source node and the destination node, including the lowest cost optical path;
The route calculation engine according to claim 10, further comprising:   The path calculation engine according to claim 13, wherein the plurality of lowest cost optical paths are separated paths. An optical network having a path calculation engine for evaluation of an optical path in an optical network, the path calculation engine having the instructions executable by a processor having access to a storage medium storing instructions , The instructions to the processor,
Generating a set of all optical paths between a source node and a destination node based on a matrix M having all optical path reachability information in an optical network, wherein the all optical paths are the source node and the destination Have a minimum number of regenerators between nodes,
Generating path cost information for the set of all optical paths, the path cost information comprising cost metric information for the set of all optical paths;
Based on the path cost information, calculate node cost information to the destination node of each node related to the all-optical path,
Generating a set of all optical paths, an optical path group having optical paths between common nodes, the path cost information, and a hierarchical guidance search graph having the node cost information;
Determining a lowest cost optical path between the source node and the destination node based on the hierarchical guidance search graph;
Let
The cost metric information indicates at least one characteristic of an optical path selected from latency, hardware cost, power consumption, excess bandwidth, and excess light penalty tolerance.
Optical network. The instruction to determine the lowest cost optical path between the source node and the destination node is:
Starting from the source node in the hierarchical guidance search graph, each continuous from each node toward the destination node in the hierarchical guidance search graph based on the route cost information and the node cost information An instruction that evaluates an optical path group to a regenerator stage that includes an instruction to select a next optical path to the next regenerator stage;
The optical network according to claim 15, further comprising: An instruction to delete an unselected optical path group that has not been selected from each node from further consideration, including an instruction to delete an unselected node from further consideration depending on the unselected optical path group; order,
The optical network according to claim 16, further comprising: Instructions for evaluating the optical path group based on the path cost information, the node cost information, and separability between selected optical paths;
An instruction to select the next optical path to be separated from a previously selected optical path;
The optical network according to claim 16, further comprising: Instructions for determining a plurality of lowest cost optical paths between the source node and the destination node, including the lowest cost optical path;
The optical network according to claim 16, further comprising:   The optical network of claim 19, wherein the plurality of lowest cost optical paths are separation paths.

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