Method for calculating routes for optical networks with multiple traffic engineering constraints

Abstract

This report provides a detailed description, accompanied by illustrative figures, of a new method for route calculation intended for traffic engineering in optical telecommunications networks. The proposed method applies a transformation that allows the selection of regenerators to be taken into account during the application of the method, thus allowing the impacts on physical metrics to be considered during route calculation. An enumeration algorithm is used to select the set of candidate routes, allowing for the consideration of multiple physical and / or logical constraints. Subsequently, the solutions are filtered, removing those that do not meet any criterion that has been modeled in a relaxed manner. The resulting set is then subjected to an objective function that classifies the solutions.

Description

1 / 11 METHOD FOR CALCULATING ROUTES FOR OPTICAL NETWORKS WITH MULTIPLE TRAFFIC ENGINEERING CONSTRAINTS

[001] This report provides a detailed description, accompanied by illustrative figures, of a new method for route calculation intended for traffic engineering in optical telecommunications networks. The method proposed here applies a topological expansion transformation that allows the selection of optical regenerators to be taken into account during the application of the method. For the selection of the set of candidate routes, a customized route enumeration algorithm is used that allows multiple physical and / or logical traffic engineering constraints to be considered.

[002] Subsequently, the solutions are filtered, thus removing those that do not meet some constraint that has been modeled in a relaxed manner. The resulting set, which includes only feasible candidate routes, is subjected to an objective function that classifies them. Field of Invention

[003] The Method for calculating routes for optical networks with multiple traffic engineering constraints, the subject of the present invention, applies to the area of ​​traffic engineering in optical telecommunications networks. Such networks are composed of optical nodes (102, 106) that are interconnected by optical links (103) with specific physical properties that affect the transmitted optical signal. Depending on the links through which the optical signal is routed, the signal is degraded in such a way that although the route is logically valid, it cannot be used physically because the signal does not reach the destination receiver with the necessary quality. The optical nodes may include optical signal regenerators (107), which can be used to recover the quality of the transmitted signal. Objectives of the Invention

[004] The method for calculating routes for optical networks with multiple traffic engineering constraints, the subject of the present invention, has as its main objective to provide a method for calculating routes in optical networks that takes into account multiple constraints, whether logical and / or physical. Another objective of the present invention is to allow Petition 870170094417, dated 05 / 12 / 2017, page 5 / 24 2 / 11 selecting regenerators when necessary to counteract the effects of optical signal degradation. Problem to be solved

[005] As described above, the Method for calculating routes for optical networks with multiple traffic engineering constraints, the subject of the present invention, provides a method for calculating routes in optical networks taking into account multiple logical and / or physical constraints, selecting, if necessary, the regenerators to be used in order to allow physical constraints to be met. On the other hand, logical constraints are important from the point of view of network administration and are part of the daily operation.

[006] Given this scenario, it becomes important that there are methods that calculate routes for establishing optical circuits that meet various types of constraints, whether physical and / or logical, and that are aware of the regenerators and select them efficiently.

[007] RFCs 5440 and 5521 (technical documents - Request for Comments) define objects that comprise the PCE (Path Computation Element) route request. These objects indicate resources that must be present, either mandatorily or desirably, in the optical path to be computed. Three types of objects are defined: nodes, interfaces, and SRLGs (Shared Risk Link Groups). The method described in this document supports the specification of these objects in the request and their consideration in the route calculation, in addition to the specific requirements of optical networks. State of the Art

[008] There are numerous patent documents and scientific articles that cite and describe techniques or methods for calculating routes for optical networks, known generically in the literature as RWA (Routing and Wavelength Assignment), but they deal with a reduced and specific scope of logical and / or physical constraints, and none of them meet the operating and application characteristics as described and proposed in the present method, the subject of this patent document. Among these documents, the following can be highlighted: Petition 870170094417, dated 05 / 12 / 2017, page 6 / 24 3 / 11

[009] The article by Y Huang et al., “CONNECTION PROVISIONING WITH TRANSMISSION IMPAIRMENT CONSIDERATION IN OPTICAL WDM NETWORKS WITH HIGH-SPEED CHANNELS,” IEEE / OSA J. Lightwave Technol., vol. 23, no. 3, pp. 982-993, Mar 2005, which addresses two techniques for route calculation considering physical constraints, but does not address the selection of regenerators; and

[010] The patent document US7171124B2, “WAVELENGTH ROUTING AND SWITCHING MECHANISM FOR A PHOTONIC TRANSPORT NETWORK”, addresses the problem by separately analyzing the choice of path from the use of regenerators, where n paths are selected and the use of regenerators is verified in these, and subsequently the wavelength is selected. The method uses a function to evaluate the quality of the solutions. The fact that the regenerators are analyzed later means that the choice of routes can invalidate the chosen routes, a situation that does not occur in the present invention, since the regenerators are taken into consideration during the choice of route. Description of the figures.

[011] Reference is made to the Figures that accompany this descriptive report, for better understanding and illustration thereof, where one can see: Figure 1 presents the context of operation of the invention. It illustrates a typical network (101), formed by nodes (102, 106) and links (103), with some nodes (106) possessing regenerator banks (107). Each of the nodes has a control plane (104) executing which in turn communicates with a PCE (105) to request a route. Figure 2 presents the steps necessary to model the problem to be submitted to the method described by this artifact. Figure 3 presents the macro-steps of the invention. Figure 4 illustrates an example of a topology before expansion. The topology consists of three nodes (401, 402, 403) and four links (411, 412, 413, 414), where one node (402) contains a bank of regenerators (421). Figure 5 illustrates the same topology as shown in Figure 4, but after expanding the topology by adding two new virtual links (501, 502). Petition 870170094417, dated 05 / 12 / 2017, page 7 / 24 4 / 11 General description of the invention.

[012] The Method for calculating routes for optical networks with multiple traffic engineering constraints, the subject of the present invention, refers to a method for calculating routes in optical networks that considers multiple constraints, taking into account both logical and physical constraints.

[013] The method uses a route enumeration algorithm (labeling algorithm), which is based on dynamic programming techniques, to find a set of candidate routes. It works as follows: given an initial route containing only the origin node, routes are derived that are extended step by step in all possible directions until the destination node is reached by all possible routes. To reduce the solution space, at each new step the feasibility of the route is checked to decide whether it remains in the derivation list or is discarded. Another concept used to optimize the search for the solution is dominance, where two routes that meet at the same node are compared to determine if one dominates the other; if this occurs, the dominated route is discarded.

[014] It is assumed that the element responsible for the calculation has access to all information about the resources available on the network, as well as their respective states. For this purpose, a link-state routing protocol can be used to disseminate information about the nodes and links on the network. RFC 7446 presents the model of the elements to be disseminated.

[015] The present method essentially comprises the following seven steps:

[016] 1) Resource filtering step: this step removes resources from the topology that should not be present in the solution; 2) Normalize metrics step: this makes the characteristics symmetrical in both directions of the links, necessary only for requests for bidirectional co-routes; 3) Expand graph step: in this step, a transformation is applied to the graph representing the optical network topology so that the use of regenerators is taken into account in the route calculation; in this step, virtual links with regeneration properties are created, representing the use of the regenerator; 4) Execute enumeration algorithm step: where the enumeration algorithm is executed to Petition 870170094417, dated 05 / 12 / 2017, page 8 / 24 5 / 11 Find the set of candidate routes that meet the submitted constraints; 5) Step to Exclude solutions that violate the relaxed constraints, this step analyzes the candidate routes from the previous step and eliminates those that violate the relaxed constraints; 6) Step to Select the wavelength, this step uses some existing method to select the wavelengths of the solutions resulting from the previous step; and 7) Step to Select the best solution, a step that scores the solutions resulting from the previous step using an objective function and selects the one with the best score.

[017] One feature of the invention is that the method does not restrict the wavelength selection technique, thus allowing the user to choose the most convenient one.

[018] Another feature is that the method does not restrict the type of DWDM grating used, thus working for both fixed and flexible gratings.

[019] The method has some limitations: it only works with monotonic metrics and only considers linear effects. Preferred embodiment and example of embodiment of the invention.

[020] The method for calculating routes for optical networks with multiple traffic engineering constraints, the subject of the present invention, works with several types of constraints, making it necessary to identify and model them before starting. Figure 2 illustrates the steps to achieve these prerequisites. This document presents a use case for some constraints, but the present method is not limited to these, and other constraints can be modeled in a similar way.

[021] The following are all the steps for applying the method, starting with the preparation steps and then applying the steps of the method proposed here:

[022] Step of Defining Scope and Constraints to be Worked On (201): The first step is to define the scope and which constraints will be worked on in the method. The constraints must necessarily be monotonic, that is, their values ​​only increase or decrease within their domain. For illustrative purposes, we will use the following constraints: - cost; OSNR; - wavelength; Petition 870170094417, dated 05 / 12 / 2017, page 9 / 24 6 / 11 - We mandate inclusion; - desirable items for exclusion.

[023] The optical network is of the fixed DWDM grid type, it does not allow wavelength conversion. However, the method is not restricted to this scenario and also applies to flexible grids with the possibility of wavelength conversion.

[024] Step of Modeling graph structures (202): the second step is to define the basic structures of the graph G = (V, E), what attributes the vertices (V) and the links (E) will have, based on the chosen constraints.

[025] Any node ve Vtem has the following property: - Optical node connectivity matrices according to the WSON standard; - Shareable regenerator bank; - minimum OSNR value up to the respective node v; - maximum value for the cost up to the respective node v.

[026] Any link ee Etem has the following properties: - cost; - the property of regenerating the link; - OSNR penalty for the link.

[027] Define Resource Container Step (203): The resource container is the data structure where candidate route information is stored; it must contain all the information necessary to validate feasibility and calculate dominance.

[028] Resource Container: - cost: the current cost of the candidate route to the present node; - Number of hops made: the number of hops between nodes on the candidate route up to the current node. This parameter is necessary because the route enumeration algorithm requires at least one non-decreasing parameter; - OSNR: the current OSNR of the candidate route to the present node; - set of nodes that must succeed: set of nodes that are mandatory or desirable in the candidate route and that have not been included up to the present node, note that the mandatory node inclusion restriction is treated in a relaxed manner; Petition 870170094417, dated 05 / 12 / 2017, page 10 / 24 7 / 11 - set of nodes that should not succeed: set of nodes that are not desirable in the candidate route and that have not been included up to the present node; - Number of regenerated links used: number of links with regeneration capabilities that were included in the candidate route up to the present node; - Set of available wavelengths: set of wavelengths available on the candidate route to the present node.

[029] Step to Define initial resource container values ​​(204): in order for the enumeration algorithm to start, it is necessary to define the initial values ​​of the container, that is, the values ​​from the origin node. - Cost: zero; - Number of jumps made: zero; OSNR: zero; - set of nodes that must succeed: a set of nodes that are mandatory for inclusion, predefined in the request; - set of nodes that should not succeed: set of nodes desirable for exclusion predefined in the request; - Number of regenerated links used: zero; - Set of available wavelengths: the result of the intersection between the input wavelengths of the source interface and the output wavelengths of the destination interface.

[030] Step to Define Resource Extension (205): In this step, it is defined how the container attributes will be changed with each extension of the candidate route, that is, given the current container and an extension link for the route, what would the resulting container be if the extension is feasible. - cost: the sum of the cost of the current node's container and the cost of the extension link; - number of hops made: the value of the current node's resource container plus one; - OSNR: If the extension link has the regeneration property, the value in the new container will be the penalty of the extension link; otherwise, it will be the addition. Petition 870170094417, dated 05 / 12 / 2017, p. 11 / 24 8 / 11 of the OSNR of the current node's resource container with the extension link penalty; - set of nodes that must succeed: the set of the current node's container minus the node corresponding to the terminal node of the extension link; - set of nodes that should not succeed each other: the set of the current node's container minus the node corresponding to the terminal node of the extension link; - Number of regenerated links used: the number of regenerated links from the current node's resource container plus one if the extension link has the regeneration property; - set of available wavelengths: in this case there are two situations: - when the extension link does not have the regeneration property: intersection of the wavelength set of the current node's resource container with the wavelength set of the extension link. - when the extension link has the regeneration property: intersection of the wavelength set of the current node's resource container with the wavelength set of the extension link and with the wavelength set supported by the regenerator.

[031] Define feasibility validation step (206): in this step the validations performed to verify whether the extension is feasible or not are defined. - Connectivity matrices and regenerator banks: the extension of the candidate route must not violate the direction constraints imposed by the connectivity matrices and regenerator banks of the current node. - OSNR: the extension must not violate the minimum OSNR value defined by the extension node; that is, the OSNR in the container must not be greater than the OSNR defined by the extension node. - Available wavelengths: the extension should not result in an empty set of wavelengths; - Cost: The extension must not violate the maximum cost value defined by the extension node. Petition 870170094417, dated 05 / 12 / 2017, p. 12 / 24 9 / 11

[032] Note that adding constraint attributes such as cost and OSNR to the feasibility comparison limits the solution values. If optimization is desired, then such attributes should not be included in the feasibility check.

[033] Step to Define Solution Dominance (207): in this step the dominance criterion is defined. Resource container 1 dominates container 2, that is, candidate route 1 dominates candidate route 2, if and only if: - The cost value of resource container 1 is less than or equal to the cost value of resource container 2; - The OSNR value of resource container 1 is less than or equal to the OSNR value of resource container 2; - the number of regenerated links used from resource container 1 is less than or equal to the number of regenerated links used from resource container 2 (implicitly the number of regenerators); - The set of available wavelengths from resource container 2 minus the set from resource container 1 is empty; - The set of desired optical switching nodes from resource container 1 is contained within the set of resource container 2; The set of unwanted optical switching nodes from resource container 1 contains the set from resource container 2.

[034] Once these steps are understood, the problem is ready to be applied to the method of the invention. The macro steps are represented in Figure 3, and are as follows:

[035] Resource Filtering Step (301): during this step, resources that must be excluded and / or that are not symmetrical are removed from the network topology. Non-symmetrical resources are understood to be, for example, a wavelength that is available in one direction of the link, but not in the opposite direction. The removal of non-symmetrical resources applies only to the case of co-routed bidirectional routes.

[036] Normalize metrics step (302): the method requires that the metrics be symmetrical with respect to direction, therefore in this step the normalization process is performed on all metrics. An example would be a link from node 1 to node 2 Petition 870170094417, dated 05 / 12 / 2017, page 13 / 24 Link 10 / 11 has a cost of 5 units and the reverse link has a cost of 7 units, so the cost of both is considered to be 7 units to reflect the worst-case scenario. This is only necessary for the case of co-routed bidirectional routes.

[037] Graph Expansion Step (303): This step aims to add virtual links that represent the selection of regenerators, so that the enumeration algorithm can execute without changes and considering the regeneration factor.

[038] The graph expansion process occurs as follows: let G = (V, E) be a graph representing a network with a set V of nodes and a set E of links, a transformation function T(G) is applied resulting in a graph G' = (V, E + R) where R corresponds to a set of virtual links with regeneration property. T(G) is a transformation in which for every link ee Ee regenerator bank at the origin node e, a virtual link rvre R is created if the link has connectivity with the regenerator bank. Every link r has the same characteristics as the link from which it originated, except for characteristics that are dependent on the regeneration property; in this case, the values ​​must be adjusted depending on the situation.An example of this situation would be wavelengths; in this case, the set of wavelengths of rde must be the result of the intersection of the wavelengths of the link ee and those supported by the regenerator bank.

[039] Figure 4 illustrates a G(400) network before the expansion process, it is composed of three nodes (401, 402, 403) and two pairs of links (411, 412 and 413, 414). Node 402 has a regenerator bank, while the others do not.

[040] Figure 5 illustrates the network G'(500), which is nothing more than the network G(400) after the transformation T(G), as can be seen, two new links were created (501 and 502), which are the links that represent the use of a regenerator at node 402.

[041] Where the virtual link 501 is derived from 412 and 502 from 413.

[041] Execute enumeration algorithm step (304): in this step the enumeration algorithm is executed, it is responsible for returning a set of candidate routes.

[042] However, to use this algorithm, it is necessary to parameterize the initialization, expansion, and dominance steps. Petition 870170094417, dated 05 / 12 / 2017, page 14 / 24 11 / 11

[043] Step to Exclude candidate routes that violate relaxed restrictions (305): in this step each candidate route is analyzed with the purpose of eliminating those that violate any restriction that has been relaxed. Typically mandatory inclusion restrictions are handled in this step.

[044] Wavelength Selection Step (306): In this step, the wavelength for the candidate route is selected; the method is independent of the technique, and a first fit can be used, for example.

[045] Step of Selecting the best candidate route (307): the last step involves scoring the candidate routes using an objective function / (s) so that the solution with the best score Min( / (s)) is then chosen.

[046] The objective function used has the following format: f(s) =Σί=οΣ-**ί,where:wí - the weight corresponding to the constraint. The greater the weight, the more impact it will have on the choice of route; - sié is the normalized measure of the constraint in the candidate route s. In fact, the value of sié depends on the nature of the constraint; if the constraint is related to a set, such as links that should ideally be excluded, it is necessary to use a similarity and / or dissimilarity measure that works with groups.

[047] It is also possible to use the invention in cases of protected routes; for this, it is sufficient to parameterize the information of the main route as constraints in the calculation of the protection route.

[048] Thus, due to the configuration and operating characteristics described above, it can be clearly seen that the METHOD FOR CALCULATING ROUTES FOR OPTICAL NETWORKS WITH MULTIPLE TRAFFIC ENGINEERING CONSTRAINTS is a new method for the State of the Art which has unprecedented conditions of innovation, inventive activity and industrialization, which make it deserving of the Privilege of Invention Patent. Petition 870170094417, dated 05 / 12 / 2017, p. 15 / 24

Claims

1 / 2 CLAIMS 1) METHOD FOR CALCULATING ROUTES FOR OPTICAL NETWORKS WITH MULTIPLE TRAFFIC ENGINEERING CONSTRAINTS, a method for calculating routes in optical networks that considers multiple constraints, taking into account both logical and physical constraints, applied to monotonic metrics and linear effects, characterized by essentially comprising the following seven steps: 1) Resource filtering step; 2) Metric normalization step; 3) Graph expansion step, in this step a transformation is applied to the graph representing the network so that the use of regenerators is taken into account in the route calculation, in this step virtual links with regeneration properties are created, which represent the use of regenerators; 4) Enumeration algorithm execution step, where the route enumeration algorithm is executed to find the set of relaxed routes that meet the submitted constraints; 5) Exclude solutions that violate the relaxed constraints step;6) Wavelength Selection Step; and 7) Best Route Selection Step, which scores the candidate routes resulting from the previous step using an objective function and selects the one with the lowest score. 2) METHOD FOR CALCULATING ROUTES FOR OPTICAL NETWORKS WITH MULTIPLE TRAFFIC ENGINEERING CONSTRAINTS, method according to claim 1, characterized by not restricting the wavelength selection technique. 3) METHOD FOR CALCULATING ROUTES FOR OPTICAL NETWORKS WITH MULTIPLE TRAFFIC ENGINEERING CONSTRAINTS, method according to claim 1, characterized by not restricting the type of grid used. 4) METHOD FOR CALCULATING ROUTES FOR OPTICAL NETWORKS WITH MULTIPLE TRAFFIC ENGINEERING CONSTRAINTS, method according to claim 1, characterized by allowing the use of a link-state routing protocol for disseminating information from nodes and links in the network. 5) METHOD FOR CALCULATING ROUTES FOR OPTICAL NETWORKS WITH MULTIPLE TRAFFIC ENGINEERING CONSTRAINTS, method according to Petition 870250096044, dated 10 / 21 / 2025, p. 21 / 27 2 / 2 claim 1, characterized by using a route enumeration algorithm (labeling algorithm), which is based on the dynamic programming technique, to find a set of possibly feasible routes. Petition 870250096044, dated 10 / 21 / 2025, p. 22 / 27

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