Patent Description:
A data communication network infrastructure, such as the Internet, can be composed of a large number of network nodes that are connected among one another. Network nodes refer to network components (e.g., clients, servers, microservices, virtual machines, serverless code instances, IoT devices, etc.) that communicate with one another according to predetermined protocols by means of wired or wireless communication links. The data communication network provides services to users according to requirements of the services, such as quality of service (QoS) commitments. Different types of services with different QoS requirements may be provided by the data communication network via different service links formed by the network nodes deployed in the network.

In a data communication network, resources for services are allocated and optimized according to a current state of the network. With arrivals of new service demands, there is often a need to migrate existing services to different sets of configurations, such as different service routes, resource allocations, or the like. In such circumstances, it is desirable to migrate the existing services smoothly such that the service disruption is minimized. Further, when a network link failure occurs, there is a need to provide restoration schemes to services that are impacted by the network link failure. For a large data communication network involving a large number of network nodes, the computation complexity to determine the restoration schemes can be high, and a computationally efficient method to provide restoration schemes in case of a network link failure is desired. It is also desired that a minimal number of service links is used to satisfy the service demands in the data communication network so as to reduce the cost of operating the network. US patent application <CIT> discloses a method of operating a telecommunications network, the telecommunications network comprising plural nodes connected by plural spans and arranged to form a mesh network, the method comprising the steps of: establishing at least one pre-configured cycle of spare capacity in the mesh network, the pre-configured cycle including plural nodes of the mesh network; and configuring the plural nodes of the pre-configured cycle, in advance of a failure, to protect a set of mutually disjoint working paths in case of failure of one of the mutually disjoint working paths, each of the mutually disjoint working paths having end nodes on the pre-configured cycle. Publication "<NPL>, introduces an extension to the method of p -cycles for network protection, wherein the main advance is the generalization of the p-cycle concept to protect path segments of contiguous working flow, not only spans that lie on the cycle or directly straddle the p -cycle.

The present invention is defined in the appended independent claims <NUM> and <NUM> to which reference should be made. Advantageous features are set out in the appended dependent claims <NUM>-<NUM> and <NUM>-<NUM>.

The accompanying drawings, which constitute part of this disclosure, together with the description, illustrate and serve to explain the principles of various example embodiments.

The following detailed description refers to the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the following description to refer to the same or similar parts. While several illustrative embodiments are described herein, modifications, adaptations and other implementations are possible. For example, substitutions, additions or modifications may be made to the components illustrated in the drawings, and the illustrative methods described herein may be modified by substituting, reordering, removing, or adding steps to the disclosed methods. Accordingly, the following detailed description is not limited to the disclosed embodiments and examples. Instead, the proper scope is defined by the appended claims.

<FIG> shows an example data communication network <NUM> in which various implementations as described herein may be practiced. Data communication network <NUM> includes, for example, a network <NUM>, network management system <NUM>, database <NUM>, network devices 120A-120E, and client devices 130A-130E. The network devices 120A-120E and client devices 130A-130E form a service network <NUM>, in which the network devices 120A-120E (collectively <NUM>) provide data services to client devices 130A-130E (collectively <NUM>). The network devices may be hardware-based or software-based switches, routers, splitters, or the like that facilitate delivery of data services to client devices <NUM>. The components and arrangements shown in <FIG> are not intended to limit the disclosed embodiments, as the system components used to implement the disclosed processes and features can vary. For example, each network device <NUM> may be associated with no, one, or many client devices <NUM>. In various embodiments, service network <NUM> may be based on one or more of on-premises network environments, virtualized (cloud) network environments, or combinations of on-premises and cloud networks. Consistent with embodiments described herein, various types of data may be communicated over service network <NUM>, such as Internet (e.g., IP protocol) data, telephony or telecommunications data, satellite data, IoT-based data, cellular data, proprietary network data, and more.

Network management system <NUM> is configured to manage service deliveries for the service network <NUM>. For example, the network management system <NUM> may determine service routes and allocate resources for services to be delivered in the data communication network <NUM>. The network management system <NUM> may also reallocate resources for the existing services when new service demands arrive at the data communication network <NUM>. In some embodiments, the network management system <NUM> may manage sequences of service migrations when multiple services are to be reconfigured in the data communication network <NUM>. In some embodiments, when a link failure occurs, the network management system <NUM> may identify restoration schemes for the disrupted service. For example, the network management system <NUM> may identify alternate service links that do not involve the failed communication link. In some embodiments, the network management system <NUM> may identify a set of service links that is sufficient to satisfy the service demands in the data communication network <NUM> and in the meantime reduce the operation cost (e.g., in terms of equipment usage, bandwidth, processing activity, monetary cost, etc.) in the network. Network management system <NUM> can be a computer-based system including computer system components, desktop computers, workstations, tablets, handheld computing devices, memory devices, and/or internal network(s) connecting the components.

Network <NUM> facilitates communication between the network management system <NUM> and the service network <NUM>. Network management system <NUM> may send data to network devices <NUM> via network <NUM> to allocate resources for services in the data communication network <NUM>. Network management system <NUM> may also receive data from network devices <NUM> via network <NUM> indicating the status of service links in the data communication network <NUM>. Network <NUM> may be an electronic network. Network devices <NUM> may be configured to receive data over network <NUM> and process/analyze queries and data. Examples of network <NUM> include a local area network (LAN), a wireless LAN (e.g., a "WiFi" or mesh network), a Metropolitan Area Network (MAN) that connects multiple LANs, a wide area network (WAN) (e.g., the Internet), a dial-up connection (e.g., using a V. <NUM> protocol or a V. <NUM> protocol), a satellite-based network, a cellular-based network, etc. In the embodiments described herein, the Internet may include any publicly-accessible network or networks interconnected via one or more communication protocols, including, but not limited to, hypertext transfer protocol (HTTP/s) and transmission control protocol/internet protocol (TCP/IP). Moreover, the electronic network may also include one or more mobile device networks, such as a Long Term Evolution (LTE) network or a Personal Communication Service (PCS) network, that allow mobile devices (e.g., client devices <NUM>) to send and receive data via applicable communication protocols, including those described above.

In the illustrated example, network devices 120A and 120E are directly connected to network <NUM>, and network devices 120B-120D connect to the network <NUM> via their connection to network device 120A and/or 120E. One of ordinary skill in the art would appreciate that network devices 120B-120D may also directly connect to the network <NUM>, or may indirectly connect to the network <NUM> through numerous other devices. Network devices <NUM> may be connected to one another via copper wire, coaxial cable, optical fiber, microwave links, or other satellite or radio communication components. Accordingly, network devices <NUM> may each have a corresponding communications interface (e.g., wireless transceiver, wired transceiver, adapter, etc.) to allow for such communications.

As shown in <FIG>, network devices 120A-120E are connected to one another. In this example, network device 120A is connected to network device 120B, network device 120B is connected to network devices 120A, 120C, and 120D, network device 120C is connected to network devices 120B, 120D, and 120E, network device 120D is connected to network device 120C, and network device 120E is connected to network device 120C. In some embodiments, a network topology may be formed to present a graphical view of the service network <NUM>, where each of the network device <NUM> corresponds to a network node or vertex in the network topology. In this disclosure, the terms "node" and "vertex" are exchangeable. The network topology also shows the interconnection relationships among the network devices. In some embodiments, the network management system <NUM> may obtain the connectivity status between the network devices and generate a network topology. In other embodiments, the network management system <NUM> may acquire the network topology from a server or a database associated with a service provider providing the service network. One of ordinary skill in the art would appreciate that the service network <NUM> illustrated in <FIG> is merely an example, and the network topology of service network <NUM> can be different from the example without departing from the scope of the present disclosure.

Network management system <NUM> may reside in a server or may be configured as a distributed system including network devices or as a distributed computer system including multiple servers, server farms, clouds, computers, or virtualized computing resources that interoperate to perform one or more of the processes and functionalities associated with the disclosed embodiments.

Database <NUM> includes one or more physical or virtual storages coupled with the network management system <NUM>. Database <NUM> may be configured to store information associated with the service network <NUM>, such as the network topology, the capability of the network devices, the services and corresponding configurations provided by the service network, and so on. Database <NUM> may also be adapted to store processed information associated with the network topology and services in the service network <NUM>, so as to facilitate efficient route configurations and resource allocations to satisfy the service demands in the service network <NUM>. The data stored in the database <NUM> may be transmitted to the network management system <NUM> and/or the network devices <NUM>. In some embodiments, the database <NUM> is stored in a cloud-based server (not shown) that is accessible by the network management system <NUM> and/or the network devices <NUM> through the network <NUM>. While the database <NUM> is illustrated as an external device connected to the network management system <NUM>, the database <NUM> may also reside within the network management system <NUM> as an internal component of the network management system <NUM>.

As shown in <FIG>, network devices 120A-120E are connected with client devices 130A-130E respectively to deliver services. As an example, client devices 130A-130E include a display such as a television, tablet, computer monitor, video conferencing console, IoT device, or laptop computer screen. Client devices 130A-130E may also include video/audio input devices such as a video camera, web camera, or the like. As another example, client devices 130A-130E include mobile devices such as a tablet or a smartphone having display and video/audio capture capabilities. While <FIG> shows one client device <NUM> connected to each network device <NUM>, one of ordinary skill in the art would appreciate that more than one client device may be connected to a network device and that in some instances a network device may not be connected to any client device.

In some embodiments, the data communication network <NUM> may include an optical network, where the network devices <NUM> are interconnected by optical fiber links. The optical fiber links may be capable of conveying a plurality of optical channels using a plurality of specified different optical wavelengths. The optical network may be based on a wavelength division multiplexing (WDM) physical layer. A WDM optical signal comprises a plurality of transmission channels, each channel carrying an information signal modulated over a carrier wavelength. For example, the network devices <NUM> may be provided with the ability to switch a channel from an input fiber to an output fiber, and to add/drop traffic. The network devices <NUM> may include a wavelength switch or an optical add/drop multiplexer that performs optical add, drop, and pass through. The network devices <NUM> may include optical or optical/electrical elements being adapted to perform to various functions such as compensating, amplifying, switching, restoring, performing wavelength conversion of incoming optical signals, etc. The optical fiber links may include dispersion compensation fibers (DCF), optical filters, amplifiers and other relevant optical components that are used for operation of optical networks. The network management system <NUM> or databased <NUM> may store topologic data includes information about optical channels and their associated wavelengths. In some embodiments, the data communication network <NUM> may include a network controller (not shown) configured to improve network utilization by providing an optimal routing and wavelength assignment plan for a given set of service demands. In the context of an optical network, a service demand is a request for a wavelength between two nodes in the network. A circuit is provisioned to satisfy a service demand and is characterized by a route and assigned wavelength number.

<FIG> shows a diagram of an example network management system <NUM>, consistent with the disclosed embodiments. The network management system <NUM> may be implemented as a specially made machine that is specially programed to perform functions relating to managing a data communication network. The special programming at the network management system <NUM> enables network management system to determine service routes and allocate resources for services to be delivered in the data communication network <NUM>.

The network management system <NUM> includes a bus <NUM> (or other communication mechanism) which interconnects subsystems and components for transferring information within the network management system <NUM>. As shown, the network management system <NUM> includes one or more processors <NUM>, input/output ("I/O") devices <NUM>, network interface <NUM> (e.g., a modem, Ethernet card, or any other interface configured to exchange data with a network), and one or more memories <NUM> storing programs <NUM> including, for example, server app(s) <NUM>, operating system <NUM>, and data <NUM>, and can communicate with an external database <NUM> (which, for some embodiments, may be included within the network management system <NUM>).

The processor <NUM> may be one or more processing devices configured to perform functions of the disclosed methods, such as a microprocessor manufactured by Intel™ or manufactured by AMD™. The processor <NUM> may comprise a single core or multiple core processors executing parallel processes simultaneously. For example, the processor <NUM> may be a single core processor configured with virtual processing technologies. In certain embodiments, the processor <NUM> may use logical processors to simultaneously execute and control multiple processes. The processor <NUM> may implement virtual machine technologies, or other technologies to provide the ability to execute, control, run, manipulate, store, etc. multiple software processes, applications, programs, etc. In some embodiments, the processor <NUM> may include a multiple-core processor arrangement (e.g., dual, quad core, etc.) configured to provide parallel processing functionalities to allow the network management system <NUM> to execute multiple processes simultaneously. It is appreciated that other types of processor arrangements could be implemented that provide for the capabilities disclosed herein.

The memory <NUM> may be a volatile or non-volatile, magnetic, semiconductor, tape, optical, removable, non-removable, or other type of storage device or tangible or non-transitory computer-readable medium that stores one or more program(s) <NUM> such as server apps <NUM> and operating system <NUM>, and data <NUM>. Common forms of non-transitory media include, for example, a flash drive a flexible disk, hard disk, solid state drive, magnetic tape, or any other magnetic data storage medium, a CD-ROM, any other optical data storage medium, any physical medium with patterns of holes, a RAM, a PROM, and EPROM, a FLASH-EPROM or any other flash memory, NVRAM, a cache, a register, any other memory chip or cartridge, and networked versions of the same.

The network management system <NUM> may include one or more storage devices configured to store information used by processor <NUM> (or other components) to perform certain functions related to the disclosed embodiments. For example, the network management system <NUM> may include memory <NUM> that includes instructions to enable the processor <NUM> to execute one or more applications, such as server apps <NUM>, operating system <NUM>, and any other type of application or software known to be available on computer systems. Alternatively or additionally, the instructions, application programs, etc. may be stored in an external database <NUM> (which can also be internal to the network management system <NUM>) or external storage communicatively coupled with the network management system <NUM> (not shown), such as one or more database or memory accessible over the network <NUM>.

The database <NUM> or other external storage may be a volatile or non-volatile, magnetic, semiconductor, tape, optical, removable, non-removable, or other type of storage device or tangible or non-transitory computer-readable medium. The memory <NUM> and database <NUM> may include one or more memory devices that store data and instructions used to perform one or more features of the disclosed embodiments. The memory <NUM> and database <NUM> may also include any combination of one or more databases controlled by memory controller devices (e.g., server(s), etc.) or software, such as document management systems, Microsoft™ SQL databases, SharePoint databases, Oracle™ databases, Sybase™ databases, or other relational databases.

In some embodiments, the network management system <NUM> may be communicatively connected to one or more remote memory devices (e.g., remote databases (not shown)) through network <NUM> or a different network. The remote memory devices can be configured to store information that the network management system <NUM> can access and/or manage. By way of example, the remote memory devices could be document management systems, Microsoft™ SQL database, SharePoint databases, Oracle™ databases, Sybase™ databases, or other relational databases. Systems and methods consistent with disclosed embodiments, however, are not limited to separate databases or even to the use of a database.

The programs <NUM> include one or more software modules configured to cause processor <NUM> to perform one or more functions of the disclosed embodiments. Moreover, the processor <NUM> may execute one or more programs located remotely from one or more components of the data communication network <NUM>. For example, the network management system <NUM> may access one or more remote programs that, when executed, perform functions related to disclosed embodiments.

In the presently described embodiment, server app(s) <NUM> causes the processor <NUM> to perform one or more functions of the disclosed methods. For example, the server app(s) <NUM> cause the processor <NUM> to determine service routes and allocate resources for services to be delivered in the data communication network <NUM>.

In some embodiments, the program(s) <NUM> may include the operating system <NUM> performing operating system functions when executed by one or more processors such as the processor <NUM>. By way of example, the operating system <NUM> may include Microsoft Windows™, Unix™, Linux™, Apple™ operating systems, Personal Digital Assistant (PDA) type operating systems, such as Apple iOS™, Google Android™, Blackberry OS™, or other types of operating systems. Accordingly, disclosed embodiments may operate and function with computer systems running any type of operating system <NUM>. The network management system <NUM> may also include software that, when executed by a processor, provides communications with network <NUM> through the network interface <NUM> and/or a direct connection to one or more network devices 120A-120E.

In some embodiments, the data <NUM> may include, for example, network configurations, requirements of service demands, routes for existing service, capacity of the network devices and each service path, and so on. For example, the data <NUM> may include network topology of the service network <NUM>, capacity of the network devices <NUM>, and capacity of the communication link between the network devices <NUM>. The data <NUM> may also include requirements of service demands and resource allocation for each service in the service network <NUM>.

The network management system <NUM> may also include one or more I/O devices <NUM> having one or more interfaces for receiving signals or input from devices and providing signals or output to one or more devices that allow data to be received and/or transmitted by the network management system <NUM>. For example, the network management system <NUM> may include interface components for interfacing with one or more input devices, such as one or more keyboards, mouse devices, and the like, that enable the network management system <NUM> to receive input from an operator or administrator (not shown).

In a data communication network, there is often a need to migrate configurations of services. For example, due to arrival of new services, resources allocated for the existing services may be changed to satisfy the demands of the new services in the network. New routes may be allocated to the existing services, and allocation of resources on a path may be reconfigured. In this disclosure, the term "path" refers to a source-destination physical or logical route (such as an A-Z path). A path can have one or more configurations, as a result of allocations of different resources, such as different wavelength assignments.

<FIG> is a diagram of an example service migration map <NUM>, consistent with the present disclosure. <FIG> illustrates configurations for services A and B in the data communication network. In the data communication network, each service demand can be identified by a tuple <s, t>, with s and t being the source and destination node of the service demand. In this example, service A that is to be delivered from source node "d" to destination node "a" can be identified by <d, a>, and service B that is to be delivered from source node "j" to destination node "g" can be identified by <j, g>. As discussed earlier, a network node refers to a network component, such as network devices <NUM>, that communicates with one another according to predetermined protocols by means of wired or wireless communication links.

As shown in <FIG>, before migration, service A is routed along path d -> c -> b -> a, and service B is routed along path j -> f -> e -> g. After service migration, service A is rerouted to link d -> f -> e -> a, and service B is rerouted to path j -> i -> h -> g. Thus, the path f ->e is part of the service route for service B before service migration, and is also part of the service route for service A after service migration. As the path f ->e is involved in the migration of services both A and B, a migration sequence is required to minimize the service disruption. In this example, it is desired to first migrate service B to remove the service B on the path f ->e, before adding service A on the path f ->e to migrate service A, such that path f -> e does not carry both services A and B during the migration phase. In doing so, the chance of service disruption due to the limited bandwidth on path f -> e is reduced. <FIG> serves as an example of service migration map. One of ordinary skill in the art would appreciate that a data communication network may provide more than two services, and there may be more than one overlapping path between migrations of the services.

<FIG> is a flowchart of an example process <NUM> for migrating communications services in a data communication network, in accordance with embodiments of the present disclosure. The steps associated with this example process may be performed by, for example, a processor of the network management system <NUM> of <FIG>. The example process <NUM> allows a service provider to migrate services in a data communication network according to a certain order so as to reduce the disruption of services during the service migration.

In step <NUM>, the network management system accesses a migration map for a plurality of communications services in a data communication network. For example, the migration map may show routes of services before and after the migration. The migration map may also identify resources allocated on paths for services, such as a wavelength configured for the service on the associated service paths. The migration map may be stored in a database connected to the network management system, such as the database <NUM>, or stored locally in the network management system. In some embodiments, the migration map may be generated separately by a network controller based on the QoS requirements of services in the network so as to satisfy the service demands and achieve efficient use of the network. In some embodiments, the migration map may be continuously or periodically updated based on the current network status or the service demands.

In some embodiments, the network management system accesses the migration map in response to a user request to retrieve a sequence of migrations for the services. For example, the user request may be received via the I/O device <NUM>. In other embodiments, the network management system may be configured to access the migration map periodically to identify whether a migration sequence is to be determined. In other embodiments, the network management system may access the migration map in response to receiving a notification that the migration map is updated and/or service migrations are about to occur. The notification may be received from a network controller that allocates routes and resources for services in the network.

In step <NUM>, the network management system identifies a communications dependency between a first service and a second service in the plurality of communications services according to the migration map. For example, the migration map may identify that the first service is configured to migrate from a first route to a second route, the second service is configured to migrate from a third route to a fourth route, and the third route overlaps with the second route. Communications dependency means that a service cannot be moved to its final state (e.g., route and wavelength) until some other service occupying overlapping spans is moved out.

<FIG> is a diagram illustrating a process <NUM> for constructing a dependency graph according to a migration map, in accordance with embodiments of the present disclosure. As shown in <FIG>, before migration, service A is routed along route R'<NUM>: d -> c -> b -> a, and service B is routed along route R1: j -> f -> e -> g. After service reconfiguration, service A is rerouted to route R'<NUM>: d -> f -> e -> a, and service B is rerouted to route R2: j -> i -> h -> g. In this example, the data communication network is an optical network, where the wavelength assigned for service A before and after migration is λ<NUM> and λ<NUM> respectively, and the wavelength assigned for service B before and after migration is λ<NUM> and λ<NUM> respectively. Thus, route R'<NUM> for service A overlaps with R1 for service B over the path f - > e, and the wavelength assigned for service A after migration is the same as the wavelength assigned for service B before migration. In this case, a directed edge from B to A is added, as shown in <FIG>. In this embodiment, for any two services α and β in the data communication network, a directed edge from β to α is added if an old route of β before migration overlaps a new route of α after migration. In an optical network, the wavelength assigned to an old route of β before migration equals the wavelength assigned to a new route of α after migration. In doing so, a dependency graph is constructed. The diagrams depicted in <FIG> are examples only and are not intended to be limiting.

Referring to <FIG>, in step <NUM>, the network management system determines, based on the identified communications dependency, a migration sequence for migrating the plurality of communications services in the data communication network. For example, based on the identified communications dependency between services A and B shown in <FIG>, the network management system determines that migration of service B should occur before migration of service A. Thus, a migration sequence (B, A) can be formed, in which service B is the first to migrate in the migration sequence, and service A is the second to migrate in the migration sequence.

In some embodiments, a dependency graph may be constructed based on the identified communications dependency of service demands in the migration map. To construct a dependency graph, for each service demand, the network management system creates a node ni in the dependency graph. The network management system then creates a directed edge from node ni to node nj if an old route of node ni before migration overlaps a new route of nj after migration. In an optical network, a directed edge is created from node ni to node nj if the wavelength assigned to an old route of ni before migration equals the wavelength assigned to a new route of nj after migration. <FIG> is an example dependency graph <NUM>, in accordance with embodiments of the present disclosure. The diagrams depicted in <FIG> are examples only and are not intended to be limiting. As shown in <FIG>, a dependency graph is constructed including service demands A-E. For example, the dependency graph shows directed edges between services A-E, such as edges A->B, A->D, D->C, C->B, and C->E. The directed edges between the services are identified using the method described above in step <NUM>. For example, an edge exists between services A and D and is directed from service A to service D, meaning that an old route of A before migration overlaps a new route of D after migration. In an optical network, the directed edge from service A to service D also means that the wavelength assigned to an old route of A before migration equals the wavelength assigned to a new route of D after migration.

In some embodiments, based on the dependency graph, a migration sequence for services can be acquired according to a topological sort of nodes in the dependency graph. For example, according to the dependency graph shown in <FIG>, a migration sequence (A, D, C, B, E) can be formed, with service A being the first to migrate in the migration sequence and service E being the last to migrate in the migration sequence. The migration sequence allows the service demands in the network to be migrated smoothly with minimal service disruption.

Referring to <FIG>, in step <NUM>, the network management system migrates the plurality of communications services from a first plurality of configurations to a second plurality of configurations according to the migration sequence. The configurations for services may include a selected route and/or a wavelength assignment for each service demand. For example, each of the services A-E shown in <FIG> may be migrated to a different route according to the order identified in the migration sequence (A, D, C, B, E). Different resources, such as bandwidth, wavelength, time slots, may also be allocated for each of the services after the migration. For example, in an optical network, each of the services A-E shown in <FIG> may also be migrated to a different wavelength. By migrating the services according to the migration sequence, the dependency relation among the migrations of service is considered, thereby reducing the service disruption caused by the migration.

In some embodiments, parallel processing can be performed to reduce the time to migrate the services. For example, the network management system may identify the vertices of the dependency graph that have no in-going edges and group them together. The group of vertices may be added to the end of the migration sequence, where migrations of communications services corresponding to the group of vertices can be performed in parallel. The network management system may then delete the group of vertices from the dependency graph and repeat the above steps until no more vertices remain in the dependency graph.

In some data communication networks, the dependency graph may include one or more cycles, where a dependency cycle starts and ends on the same service, making it difficult to determine the migration sequence based on the dependency graph. <FIG> is a diagram illustrating a dependency cycle in a data communication network, in accordance with embodiments of the present disclosure. The example diagram depicted in <FIG> is an example only and is not intended to be limiting.

As shown in <FIG>, the left diagram illustrates a network graph <NUM> including nodes a-n and connectivity between the nodes a-n. Services A, B, C are provided by the network, where service A <j, b> is from source node "j" to destination node "b", service B <a, g> is from source node "a" to destination node "g", and service C <f, l> is from source node "f" to destination node "l". As shown in <FIG>, path <NUM>, a->b, is an overlapping path between service A and service B, path <NUM>, f->g, is an overlapping path between service B and service C, and path <NUM>, j->l, is an overlapping path between service A and service C. In this example, service A is to be migrated to another wavelength that is the same as an wavelength configuration for service B before migration of service B, service B is to be migrated to another wavelength that is the same as an wavelength configuration for service C before migration of service C, and service C is to be migrated to another wavelength that is the same as an wavelength configuration for service A before migration of service A. As a result, a cycle is formed in the corresponding dependency graph <NUM>, with directed edges from service B to service A, service C to service B, and service A to service C. The dependency cycle presents a deadlock condition such that it is difficult to determine the migration sequence of services A, B, C based on the dependency graph <NUM>. For example, if a migration sequence (A, C, B) is used, service A cannot migrate to the new wavelength without first migrating service C out of its old wavelength, causing a disruption of service A.

<FIG> is a flowchart of an example process <NUM> for migrating communications services in a data communication network, consistent with the disclosed embodiments. The steps associated with this example process may be performed by, for example, a processor of the network management system <NUM> of <FIG>. The example process <NUM> provides a method to migrate services in a data communication network when there are one or more cycles in the dependency graph of the services.

In step <NUM>, the network management system constructs a communications dependency graph identifying communications dependencies among a plurality of services in a data communication network. For example, the method described above in connection with <FIG> and <FIG> can be used to construct the communications dependency graph. The communications dependency graph includes a plurality of vertices, each of the plurality of vertices corresponding to a pre-migration configuration and a post-migration configuration of a service in the data communication network. In this disclosure, the terms "node" and "vertex" may be used interchangeably. For each service demand di in the data communication network, a corresponding node ni is created in the communications dependency graph. A directed edge from node ni to node nj is created in the communications dependency graph if the current pre-migration route of service di overlaps with the final post-migration route of service dj in the migration map. In an optical network, to create a directed edge from node ni to node nj, it is also required that the current pre-migration wavelength assignment of service di be the same as the final post-migration wavelength assignment of service dj.

In step <NUM>, the network management system identifies one or more cycles in the communications dependency graph. For example, like the cycle <NUM> shown in <FIG>, each of the cycles may include at least three vertices corresponding to at least three services in the plurality of communications services. In some implementations, the network management system may look for a cycle that starts and ends on the same vertex to detect the cycle. If no cycle is detected in the dependency graph, the network management system may determine a migration sequence according to the method described in connection with <FIG>.

In step <NUM>, the network management system identifies a special vertex in each of the one or more cycles. For example, the network management system may identify node A in the dependency cycle <NUM> of <FIG> as a special vertex. As another example, the network management system may identify node B in the dependency cycle <NUM> of <FIG> as a special vertex. In some embodiments, a node corresponding to a service that can be delivered using a temporary wavelength different from the pre-migration wavelength and post-migration wavelength may be selected as the special vertex. The process <NUM> does not limit how a special vertex is chosen in a dependency cycle.

In step <NUM>, the network management system breaks each of the one or more cycles based on the special vertex. <FIG> is a diagram illustrating a process <NUM> for breaking a dependency cycle, in accordance with embodiments of the present disclosure. As shown in the left diagram of <FIG>, node A in the dependency cycle <NUM> is identified as the special vertex, where node A corresponds to service A with a pre-migration configuration of route R<NUM> with wavelength λ<NUM> and a post-migration configuration of route R<NUM> with wavelength λ<NUM>. After identifying the special vertex, a temporary wavelength may be used to break the dependency cycle <NUM>. As shown in the right diagram of <FIG>, node A is first migrated to a temporary wavelength λtemp, and an additional node A' may be added to the dependency graph. The additional node A' corresponds to a pre-migration configuration of route R<NUM> with wavelength λtemp and a post-migration configuration of route R<NUM> with wavelength λ<NUM>. A directed edge from A to A' may also be added in the acyclic dependency graph <NUM>. In doing so, the dependency cycle is broken into an acyclic dependency graph <NUM>, and a migration sequence may be determined based on the acyclic dependency graph <NUM>. When the dependency graph includes multiple cycles, each of the cycles can be broken into an acyclic dependency graph using the above-described process.

In step <NUM>, the network management system determines, based on the broken cycles, a migration sequence for migrating the plurality of communications services. For example, after the dependency cycle <NUM> in the left diagram of <FIG> is broken into the acyclic dependency graph <NUM>, a migration sequence (A, C, B, A') may be determined according to the topological sort of the acyclic dependency graph <NUM>. In the migration sequence (A C B A'), service A is moved twice, the first time being migrated to a temporary wavelength and the second time being migrated to the final post-migration route and wavelength of service A. By using the temporary wavelength to break the dependency cycle and determine a migration sequence, the deadlock condition of the dependency cycle is resolved, and the services can transit to the post-migration configurations smoothly with minimal service disruption.

In a data communication network, when a network link failure occurs, restoration paths will need to be provided for services affected by the network link failure. Computing the restoration paths may be complex in a large network, and the computation may be performed at a central server which distributes the restoration paths to the network devices via configuration instructions. The configuration instructions may have a large size to include restoration paths for all possible link failures and link failure combinations. The disclosed embodiments provide a data structure that can be computed at a central service and sent to the network devices. The network devices may then compute the restoration paths using the data structure to satisfy the service demands when a network link failure occurs.

<FIG> is a diagram illustrating a network graph <NUM> in a data communication network, in accordance with embodiments of the present disclosure. As shown in <FIG>, the network graph <NUM> contains network nodes {A, B, C, D, E, F}. The direct connection between two nodes is referred to as an edge, such as the connection between (A, B). As shown in <FIG>, the network graph <NUM> includes <NUM> edges {e<NUM>,. , e<NUM>}, i.e., the connections between nodes (E, F), (A, B), (A, D), (A, C), (C, E), (C, D), (B, D), (B, F), (D, E), (D, F), respectively. If any of the edges {e<NUM>,. , e<NUM>}fails, a service that currently routes through the failed edge will need to be rerouted to avoid the failed edge. In some circumstances, there could be failures with multiple edges in the network, and restoration paths will need to be provided for services that routes though any of the failed edges to avoid any of the failed edges.

In this example, six service links {r<NUM>,. , r<NUM>} are provided to satisfy the service demands, where each service link is a path in the network graph <NUM>. In this disclosure, a path of a service link refers to a series of service paths in which an end vertex of a service path is the beginning vertex of a next service path. For example, Table <NUM> shows paths of service links {r<NUM>,.

A path of a service link satisfies a service demand <x, y> if the beginning vertex of the first service path is x and the end vertex of the last service path is y. For example, as shown in <FIG>, service link r<NUM> consists of a path through nodes (A, C, D), and service link r<NUM> consists of a path through nodes (A, B, D, E).

In this example, there is a service demand <A, F> in the network, which may be satisfied by service path (r<NUM>, r<NUM>). If any of the edges among {e<NUM>,. , e<NUM>} fail, a restoration path may need to be found for service demand <A, F>. For example, if edge e<NUM> fails, no restoration path is needed. In the event of a link failure in edge e<NUM>, as the current service path (r<NUM>, r<NUM>) routes though e<NUM>, a restoration path not routing through e<NUM>, such as service path (r<NUM>, r<NUM>), will need to be found to satisfy the service demand. In the event of a link failure in edge e<NUM>, as the current service path (r<NUM>, r<NUM>) routes though e<NUM>, a restoration path not routing through e<NUM>, such as service path (r<NUM>, r<NUM>), will need to be found to satisfy the service demand. In the event of link failures in both edges e<NUM> and e<NUM> occur, a restoration path not routing through e<NUM> or e<NUM>, such as service path (r<NUM>, r<NUM>), will need to be found to satisfy the service demand. For a large network with a large number of service demands, the number of restoration paths that need to be pre-computed can be large. As a result, it could take a large amount of storage space in the central server and network devices to store the restoration paths given the possible link failures in different edges or edge combinations. The disclosed embodiments provide a method to identify the restoration paths without having to store all the paths for each service demand and each series of link failures.

<FIG> is a flowchart of an example process <NUM> for providing restoration paths in a data communication network, consistent with the disclosed embodiments. The steps associated with this example process is described in relation to a network management system, such as network management system <NUM> of <FIG>. One of ordinary skill in the art would appreciate that the steps associated with this example process may also be performed by, for example, a processor of the network devices <NUM> or a server of the data communication network. The example process <NUM> allows a network device or a network management system to provide restoration paths in a data communication network without having to store all the paths for each service demand and each series of link failures.

In step <NUM>, the network management system identifies a failure in one or more service paths of the data communication network. For example, the network management system may identify a link failure by detecting service degradation in one or more services currently provided by the data communication network. As another example, the network management system may identify a link failure by receiving feedback from network devices indicating a failure to send or receive data by the network devices. Other methods known by one of ordinary skill in the art may be used to identify a failure in one or more service paths of the data communication network, which are not describe herein for the sake of brevity.

In step <NUM>, the network management system determines one or more affected service links in the data communication network based on the identified failure and a first data structure. In some embodiments, the first data structure includes a plurality of service paths and one or more corresponding service links that use the service path. <FIG> is a diagram illustrating another network graph <NUM> in a data communication network, in accordance with embodiments of the present disclosure. As shown in <FIG>, there are seven service links {r<NUM>,. , r<NUM>} provided by the data communication network, where each service link consists of one or more service paths. The service links{r<NUM>,. , r<NUM>}that can be used to satisfy service demands and their corresponding metrics are provided in Table <NUM>. The metric indicates a cost associated with the service links and may be additive in service links that includes two or more edges.

The first data structure may include each of the service paths, such as each edge in the network graph, and the corresponding service link that use the path, as shown in Table <NUM>. Here, a path (x, y) represents the path between node x and node y.

As shown in Table <NUM> above, in this example network, the first data structure includes each edge of the network graph and the corresponding service links that uses the edge. For example, for the edge (A, B), the only service link that uses edge (A, B) is r<NUM>, and for the edge (B, D), both service links r<NUM> and r<NUM> use edge (B, D). Using the first data structure, the network management system can determine the affected service links in the data communication network when one or more service paths of the network, i.e., edges of the network graph, fail to operate properly. For example, in the event edge (B, D) fails, it can be determined that the affected service links include r<NUM> and r<NUM> using the first data structure in Table <NUM>.

In step <NUM>, the network management system determines one or more affected service demands based on the affected service links and a second data structure. In some embodiments, the second data structure includes a plurality of service links provided by the data communication network and one or more service demands corresponding to one or more of the service links. The one or more service demands in the second data structure require service delivered from a first service node to a second service node, and corresponding service links can be used to satisfy the corresponding service demands. Table <NUM> provides an example of the second data structure for the network graph <NUM> shown in <FIG>.

As shown in Table <NUM> above, in this example network, service links r<NUM>, r<NUM>, r<NUM>, and r<NUM> each are used by one corresponding service demand, service links r<NUM> and r<NUM> are not used by any service demand, and service link r<NUM> is used by two service demands. Using the second data structure, the network management system can determine the affected service demands in the data communication network when one or more service links of the network are affected because of a failure in one or more network paths.

In step <NUM>, the network management system, for each of the affected service demands, determines one or more allowed service links by removing the affected service links from a set of corresponding service links for the affected service demands. In some embodiments, the network management system constructs a network graph including a plurality of service nodes and one or more service links for each of the affected service demands, where the affected service links are excluded from the network graph. Using this network graph, the allowed service links for the affected service demands may be determined. For example, referring to <FIG>, in the event service link r<NUM> and service demand <E, D> are affected, the network management system may create a new network graph by removing service link r<NUM> from the network graph <NUM>, so as to determine the allowed service links for service demand <E, D>.

In some embodiments, the network management system may determine the allowed service links for the affected service demands based on a third data structure. The third data structure includes a plurality of service demands and a corresponding set of service links that can be used by the service demand. In some implementations, the third data structure may be predefined by a network server. Table <NUM> provides an example of the third data structure for the network graph <NUM> shown in <FIG>.

As shown in Table <NUM>, a number of service links are allowed for each of the service demands. For example, referring to <FIG>, in the event service link r<NUM> and service demand <E, D> are affected, the network management system may remove r<NUM> from the corresponding set of service links in the third data structure and determine that the allowed service links for service demand <E, D> are{r<NUM>, r<NUM>, r<NUM>, r<NUM>, r<NUM>}.

In step <NUM>, the network management system for each of the affected service demands, determines one or more restoration paths based on the one or more allowed service links. In some embodiments, the restoration paths are determined based on a fourth data structure. The fourth data structure includes the service links provided by the data communication network, one or more corresponding service paths, and a corresponding cost metric. For example, Table <NUM> described above may be a fourth data structure for the network illustrated in <FIG>. In some embodiments, the restoration paths are determined by using a Dijkstra's algorithm. For example, the network management system may construct another network graph based on the allowed service links identified in step <NUM> and using information in the fourth data structure. The network management system may then run the Dijkstra's algorithm on the constructed network graph to determine the restoration paths for the affected service demands. One of ordinary skill in the art would understand that Dijkstra's algorithm is an algorithm for finding the shortest paths between nodes in a graph, and the details of the Dijkstra's algorithm are not provided in this disclosure. Methods known to one of ordinary skill in the art to implement the Dijkstra's algorithm can be used to identify restoration paths for the affected service demands.

By using the first and second data structures, the example process <NUM> allows the restoration paths to be determined in real time when a network link failure occurs. Moreover, the size of the first and second data structures are relatively small, and so it does not take much storage space to store the first and second data structures. This also allows the data structures to be stored in the network devices. In some embodiments, the first, second, third, and fourth data structures are stored in the network devices. Further, because constructing a new network graph and running the Dijkstra's algorithm are computationally efficient, the network devices may be able to determine the restoration paths in a distributed manner rather than relying on a network management system or a server to determine the restoration paths.

<FIG> is a diagram illustrating an example process <NUM> for identifying affected service demands when one or more service paths in a data communication network fail, in accordance with embodiments of the present disclosure. The steps associated with this example process is described in relation to a network management system, such as network management system <NUM> of <FIG>. One of ordinary skill in the art would appreciate that the steps associated with this example process may also be performed by, for example, a processor of the network devices <NUM> or a server of the data communication network.

In this example, the network graph <NUM> in <FIG> is used as the graph in the data communication network, and a link failure in edges (B, D) and (A, D) is identified. Thus, restoration paths need to be provided for service demands affected by the link failure. As shown in <FIG>, after the link failure is identified, the network management system determines service links that are affected by the identified failure. The network management system may use the first data structure shown in Table <NUM> above to identify the affected service links. As shown in Table <NUM>, service links r<NUM> and r<NUM> are affected by the failure of edge (B, D), and service link r<NUM> is affected by the failure of edge (A, D). Then service demands that use the affected service links may be determined using the second data structure shown in Table <NUM> above. According to Table <NUM>, service demand <A, F> is affected by the affected service link r<NUM>, service demands <A, F> and <E, D> are affected by the affected service link r<NUM>, and no service demand is affected by the affected service link r<NUM>. Thus, the set of service demands that are affected by the link failure includes service demands <A, F> and <E, D>. The network management system then needs to determine restoration paths for rerouting the affected service demands.

<FIG> is a diagram illustrating another network graph <NUM> for identifying restoration paths for affected service demands in a data communication network, in accordance with embodiments of the present disclosure. As shown in <FIG>, the network management system constructs another network graph <NUM> for the affected service demand <A, F> by removing the affected service links r<NUM>, r<NUM>, and r<NUM> from the original network graph <NUM> before the link failure occurs. Because service link r<NUM> is not included in the allowed service links for service demand <A, F> identified in the third data structure of Table <NUM>, r<NUM> is also removed from the network graph <NUM>. As a result, the network graph <NUM> contains service links r<NUM>, r<NUM>, and r<NUM>. Because node C is not an end point for any of the allowed service links for service demand <A, F>, node C is also removed from the network graph <NUM>, and the network graph <NUM> contains nodes A, B, D, E, F. Based on the network graph <NUM>, the network management system may run the Dijkstra's algorithm and determine that the path (r<NUM>, r<NUM>) may be used as the restoration path for service demand <A, F>. One of ordinary skill would understand that similar processing can be performed to identify the restoration path for the other affected service demand < E, D >. Further, one of ordinary skill would understand that the network graphs <NUM> and <NUM> are described herein for illustrative purposes, and the disclosed embodiments can be used to identify restoration paths for different network graphs and service demands provided in the network.

In a data communication network, when a network link failure occurs, restoration paths need to be provided for services affected by the network link failure. Given a set of demands in the data communication network, it is desirable to assign service links to the service demands such that when one or two edges fail, the service demands can still be satisfied. For example, referring to the third data structure in Table <NUM> above, it is desirable to assign the service links to the service demands <A,B>, <E,D>, and <A,F> such that when one or two edges fail, and as a result, the relevant assigned service links fail, the service demands can be satisfied using the remaining available service links. The disclosed embodiments provide a cycle structure that can be used to assign the service links to the service demands such that when one or two assigned service links fail, the service demands can still be satisfied using the remaining available service links.

<FIG> is a flowchart of an example process <NUM> for restoring service demands in a data communication network, consistent with the disclosed embodiments. The steps associated with this example process is described in relation to a network management system, such as network management system <NUM> of <FIG>. One of ordinary skill in the art would appreciate that the steps associated with this example process may also be performed by, for example, a processor of the network devices <NUM> or a server of the data communication network. The example process <NUM> allows service demands to be restored by using remaining available service links when one or two service links assigned to the service demands fail.

In step <NUM>, the network management system identifies a communications route cycle through a set of vertices. The set of vertices includes a plurality of vertices, each of the plurality of vertices corresponding to an end point of at least one service demand. The plurality of vertices includes two vertices corresponding to end points of each of the service demands. In this disclosure, a vertex corresponds to a network node, such as a network device <NUM>, and the terms "vertex" and "node" may be used interchangeably.

<FIG> is a diagram illustrating a communications route cycle <NUM> in a data communication network, in accordance with embodiments of the present disclosure. The communications route cycle <NUM> is a part of a path cycle. A path cycle refers to a cycle combined with the additional paths that are disjoint to the edges of the cycle. In this example, the service demands in the data communication network include <A, C>, <B, E> <E, G>, and one or more service links are to be assigned to each of the service demands. As shown in <FIG>, the communications route cycle <NUM> includes vertices A, B, C, E, G, which are end points, i.e., source nodes or destination nodes, of the service demands <A, C>, <B, E>, <E, G>. The communications route cycle <NUM> also includes vertices D, F, H that are not end points of a demand. As shown in <FIG>, the communications route cycle <NUM> consists of a cycle {A, B, C, D, G, F, E, A} that goes through the vertices that are end points A, B, C, E, G of the service demands <A, C>, <B, E>, <E, G> and vertices D, F that are not end points of a demand. One of ordinary skill in the art will understand that the communications route cycle <NUM> illustrated in <FIG> is an example of a communications route cycle, and a communications route cycle may be different from this example without departing from the scope of the present disclosure.

In step <NUM>, the network management system identifies a path between a pair of vertices among the plurality of vertices, the pair of vertices corresponding to end points of a service demand, where the path is disjoint to the communications route cycle. In some embodiments, the identified path is identified based on it being the shortest among paths between the pair of vertices that are -disjoint to edges of the communications route cycle. In other embodiments, the identified path is identified based on it having the least cost among paths between the pair of vertices that are disjoint to the edges of the communications route cycle.

Referring to <FIG>, the network management system may identify a path between any pair of end points of service demands <A, C>, <B, E>, <E, G>. For example, the network management system may identify the path A->H->C that is disjoint to the edges of the communications route cycle <NUM> for service demand <A, C>. The network management system may further identify the path B->E for service demand <B, E> that is disjoint to the communications route cycle <NUM> and the path E->H->G for service demand <E, G> that is disjoint to the edges of the communications route cycle <NUM>. As a result, a path that is disjoint to the communications route cycle <NUM> is identified for each of the service demands <A, C>, <B, E>, <E, G>.

In step <NUM>, the network management system determines a set of service links corresponding to the one or more service demands based on the identified path and communication route cycle. In some embodiments, the set of service links includes the identified path for the corresponding service demand. Continuing with the example communications route cycle <NUM> illustrated in <FIG>, the network management system may assign service links {A->B->C, A->E->F->G->D->C, A->H->C} to service demand <A, C>. With this assignment, when any two edges fail in the communications route cycle <NUM>, the service demand <A, C> can still be satisfied with other available service links assigned to the service demand <A, C>. As another example, the network management system may assign service links {B->A->E, B->C->D->G->F->E, B->E} to service demand <B, E>, such that when any two edges fail in the communications route cycle <NUM>, the service demand < B, E > can still be satisfied with other available service links assigned to the service demand < B, E >. As a further example, the network management system may assign service links {E->F->G, E->A->B->C->D->G, E->H->G} to service demand <E, G>, such that when any two edges fail in the communications route cycle <NUM>, the service demand < E, G > can still be satisfied with other available service links assigned to the service demand < E, G >.

In some embodiments, the network management system may assign sets of service links for the service demands by solving the service demands together as a set. For example, the network management system may determine a first set of service links on the communications route cycle that terminate at end points of the set of demands in the data communication network. The network management system may assign the first set of service links to every demand. For example, referring to <FIG>, the network management system may identify a first set of service links {A->B, B->C, C->D->G, G->F->E, E->A} for service demands <A, C>, <B, E>, <E, G>. Each of the service links A->B, B->C, C->D->G, G->F->E, and E->A is on the communications route cycle <NUM> and terminates at end points of service demands <A, C>, <B, E>, or <E, G>. The service links {A->B, B->C, C->D->G, G->F->E, E->A} are assigned to each of the service demands <A, C>, <B, E>, <E, G>. The network management system may additionally assign the disjoint path with the same end points as the service demand to the corresponding service demand. For example, the network management system may assign an additional service link A->H->C for service demand <A, C>, an additional service link B->E for service demand <B, E>, and an additional service link E->H->G for service demand <E, G>. That is, the service links assigned for service demand <A, C> are {A->B, B->C, C->D->G, G->F->E, E->A, A->H->C}, the service links assigned for service demand <B, E> are {A->B, B->C, C->D->G, G->F->E, E->A, B->E}, and the service links assigned for service demand <E, G> are {A->B, B->C, C->D->G, G->F->E, E->A, E->H->G }. By assigning a first set of service links for the set of service demands in the data communication network jointly, the total number of service links needed for the service demands may be reduced compared to assigning service links for each of the service demands separately as illustrated above.

The network management system first identifies a communications route cycle that is the shortest among all cycles going through all end points of the given service demands. For each service demand, the network management system may then identify a path that is shortest among all paths between the end points of the service demand that are disjoint to the edges of the communications route cycle. In other embodiments, the network management system may first identify a communications route cycle that is of the least cost among all cycles going through all end points of the given service demands. For each service demand, the network management system may then identify a path that is of the least cost among all paths between the end points of the service demand that are disjoint to the edges of the communications route cycle.

<FIG> is a flowchart of another example process <NUM> for restoring service demands in a data communication network, consistent with the disclosed embodiments. The steps associated with this example process is described in relation to a network management system, such as network management system <NUM> of <FIG>. One of ordinary skill in the art would appreciate that the steps associated with this example process may also be performed by, for example, a processor of the network devices <NUM> or a server of the data communication network. The example process <NUM> allows service demands to be restored by using remaining available service links when one or two edges fail and cause the resulting service links assigned to the service demands fail.

In step <NUM>, the network management system identifies a communications route cycle through a set of vertices. The set of vertices includes a plurality of vertices, each of the plurality of vertices corresponding to an end point (i.e., a source or destination node) of at least one service demand. The plurality of vertices includes two vertices corresponding to end points of each of the service demands.

<FIG> is a diagram illustrating another communications route cycle <NUM> in a data communication network, in accordance with embodiments of the present disclosure. The communications route cycle <NUM> may also be referred to as a star cycle. In this example, the set of service demands in the data communication network includes <A, B>, <B, E>, <A, F>, <E, G>, <A, C, <C, E>, <F, G>, <B, G>. One or more service links are to be assigned to each of the service demands. As shown in <FIG>, the communications route cycle <NUM> includes vertices A, B, C, E, F, G, which are end points, i.e., source nodes or destination nodes, of the set of service demands. The communications route cycle <NUM> also includes vertex D that is not an end point of a demand. As shown in <FIG>, the communications route cycle <NUM> consists of a cycle {A, B, C, D, G, F, E, A} that goes through the end points of the set of service demands A, B, C, E, F, G. One of ordinary skill in the art will understand that the communications route cycle <NUM> illustrated in <FIG> is an example of a communications route cycle, and a communications route cycle may be different from this example without departing from the scope of the present disclosure.

In step <NUM>, the network management system identifies a path between a pair of antipodal vertices on the communications route cycle among the plurality of vertices, where the path is disjoint to the edges of the communications route cycle. In some embodiments, the identified path is identified based on it being the shortest among paths between the pair of antipodal vertices that are disjoint to the communications route cycle. In other embodiments, the identified path is identified based on it having the least cost among paths between the pair of antipodal vertices that are disjoint to the edges of the communications route cycle.

Referring to <FIG>, the network management system may identify pairs of antipodal vertices including (A, G), (B, F), and (C, E). The network management system may then identify paths between the pairs of antipodal vertices that are disjoint to the communications route cycle <NUM>. For example, the network management system may identify the path A->H->G that is disjoint to the edges of the communications route cycle <NUM> between the antipodal vertices (A, G). The network management system may further identify the path B->F for the antipodal vertices (B, F) that is disjoint to the edges of the communications route cycle <NUM> and the path C->H->E for the antipodal vertices (C, E) that is disjoint to the edges of the communications route cycle <NUM>. As a result, a path that is disjoint to the communications route cycle <NUM> is identified for each of the pairs of antipodal vertices.

In step <NUM>, the network management system determines a set of service links corresponding to the set of one or more service demands based on the identified path and communication route cycle. In some embodiments, the set of service links includes a service link that contains the identified path for the corresponding antipodal vertices. Continuing with the example communications route cycle <NUM> illustrated in <FIG>, the network management system may assign service links {A->B, B->C, C -> D -> G, G->F, F->E, E->A, A->H->G, C->H->E , B->F} to service demand <A, B>. With this assignment, when any two edges fail in the communications route cycle <NUM>, the service demand < A, B > can still be satisfied with other available service links assigned to the service demand < A, B >. As another example, the network management system may assign the same service links {A->B, B->C, C ->D -> G, G->F, F->E, E->A, A->H->G , C->H->E, B->F} to service demand <B, E>, such that when any two edges fail in the communications route cycle <NUM>, the service demand < B, E > can still be satisfied with other available service links assigned to the service demand < B, E >. As a further example, the network management system may assign the same service links {A->B, B->C, C -> D -> G, G->F, F->E, E->A, A->H->G, C->H->E, B->F} to service demand <E, G>, such that when any two edges fail in the communications route cycle <NUM>, the service demand < E, G > can still be satisfied with other available service links assigned to the service demand < E, G >.

The network management system first identifies a communications route cycle that is the shortest among all cycles going through all end points of the given service demands. The network management system may then identify pairs of antipodal vertices in the communications route cycle. For each pair of antipodal vertices, the network management system may then identify a path that is shortest among all paths between the pair of antipodal vertices that are disjoint to the edges of the communications route cycle.

In other embodiments, the network management system may first identify a communications route cycle that is of the least cost among all cycles going through all end points of the given service demands. The network management system may then identify pairs of antipodal vertices in the communications route cycle. For each pair of antipodal vertices, the network management system may then identify a path that is of the least cost among all paths the pair of antipodal vertices that are disjoint to the edges of the communications route cycle.

In some implementations, the network management system may identify both a path cycle, i.e., a communications route cycle that includes disjoint paths to the edges of the cycle between end points of service demands, and a star cycle, i.e., a communications route cycle that includes disjoint paths to the edges of the cycle between antipodal nodes of the cycle, for a given set of service demands. The network management system may determine which cycle would lead to a shorter path for the service links corresponding to the service demands and use that cycle to determine the service links.

In a data communication network, there may be a large number of service demands to be satisfied. It is required to provide service links to satisfy the service demands, and in the meantime, it is desired to reduce the service links to satisfy the service demands to the extent possible. The disclosed embodiments provide a method for determining sets of service demands from a plurality of service demands based on connected components in the network graph. The service links to be provided for satisfying the plurality of service demands are then determined based on the sets of service demands by using a set cover algorithm.

<FIG> is a flowchart of an example process <NUM> for determining service links for a data communication network, consistent with the disclosed embodiments. The steps associated with this example process is described in relation to a network management system, such as network management system <NUM> of <FIG>. One of ordinary skill in the art would appreciate that the steps associated with this example process may also be performed by, for example, a processor of the network devices <NUM> or a server of the data communication network. The example process <NUM> allows using a reduced number of service links to satisfy the service demands in the data communication network.

In step <NUM>, the network management system identifies a plurality of connected components in a service demand graph. Each of the connected components is formed by one or more edges and one or more vertices, and the number of edges included in each of the plurality of connected components is less than or equal to a predetermined size threshold. In some embodiments, a service demand graph is constructed identifying sets of service demands that are candidates for grooming in the data communication network. The service demand graph includes a plurality of vertices corresponding to end points of service demands. In the service demand graph, a first vertex corresponding to first service demand is connected with a second vertex corresponding to the second service demand with an edge when the first service demand and the second service demand have a common service demand end point. The network management system may determine the connected components based on the service demand graph.

<FIG> is a diagram illustrating a service demand graph <NUM> in a data communication network, in accordance with embodiments of the present disclosure. In this example, the service demands in the data communication network includes <A, B>, <A, C>, <A, D>, <E, B>, <E, C>, and <E, D>. A predetermined size threshold is set to two in this example. As shown in <FIG>, the service demand graph <NUM> includes all the end points of the service demands in the data communication network, and the source and destination nodes of a service demand are connected with an edge. For example, the source and destination nodes of the service demand <A, B> are connected by an edge between node A and node B. As another example, the source and destination nodes of the service demand <E, B> are connected by an edge between node E and node B. As a common end point B is shared between service demands <A, B> and <E, B>, the service demands <A, B> and <E, B> form a connected component (AB, EB) via the shared node B.

Based on service demand graph <NUM>, the connected components with edge-size less than or equal to the predetermined size threshold, which is set to two in this example, can be identified. For example, the connected components with size equaling one include the edge formed by each service demand, i.e., (AB), (AC), (AD), (EB), (EC), (ED). Here (x, y) denotes an edge between node x and node y. The connected components with size equaling two include two connected edges in the service demand graph, i.e., (AB, AC), (AB, AD), (AC, AD), (EB, EC), (EB, ED), (EC, ED), (AB, EB), (AC, EC), (AD, ED). As a result, the set of connected components with size less than or equal to the predetermined size threshold includes the follows: {(AB), (AC), (AD), (EB), (EC), (ED), (AB, AC), (AB, AD), (AC, AD), (EB, EC), (EB, ED), (EC, ED), (AB, EB), (AC, EC), (AD, ED)}.

In step <NUM>, the network management system calculates a cost associated with each of the plurality of connected components. For example, costs for the connected components in the service demand graph <NUM> may be calculated. The cost for the connected component may depend on the number of service links required for the connected component. For example, the cost for connected component (AC) may be higher than the cost for connected component (AB) when the connected component (AC) requires more service links than the connected component (AB). The cost for the connected component may also take into account the amount of resources required to satisfy the service demand(s), the capacity of the service links, the quality of service requirements for the service demand(s), or the like. Table <NUM> provides an example cost for the connected components in the service demand graph <NUM>.

In step <NUM>, the network management system determines sets of service demands based on the plurality of connected components and the calculated cost by using a set cover algorithm. The sets of service demands may be used to determine a plurality of service links for the plurality of service demands in the data communication network. In some embodiments, the set cover algorithm may include a greedy algorithm or an integer linear programming. The set cover algorithm identifies a subset of connected components with the least cost to cover the plurality of service demands in the data communication network. For example, using a set cover algorithm on the connected components listed on Table <NUM>, a set cover {(AB), (EB, EC), (AC, AD), (EB, ED)} may be determined, which corresponds to the sets of service demands for determining the service links. The set cover covers all service demands in this example network with a total cost of <NUM>.

In step <NUM>, the network management system determines sets of service links for the plurality of service demands based on the sets of service demands. For example, the network management system may determine sets of service links used for the set cover {(AB), (EB, EC), (AC, AD), (EB, ED)}. The service links assigned for each connected component may be predetermined by a network server. The sets of service links can be used to satisfy other service demands in the data communication network, such as service demands <A, C>, <A, D>, <E, B>, <E, C>, and <E, D>. For example, Table <NUM> shows service links assigned to each connected component in the service demand graph <NUM>. When the sets of service demands are determined to be{(AB), (EB, EC), (AC, AD), (EB, ED)}, the sets of service links are determined to include the service links assigned to each connected component in the sets of service demands, which are {r<NUM>, r<NUM>, r<NUM>, r<NUM>, r<NUM>, r<NUM>} for the sets of demands{(AB), (EB, EC), (AC, AD), (EB, ED)}.

In exemplary embodiments, a non-transitory computer-readable storage medium including instructions is also provided, and the instructions may be executed by a device (such as a computer), for performing the above-described methods. For example, the non-transitory computer-readable storage medium may be a read-only memory (ROM), a Random Access Memory (RAM), an electrically erasable programmable read-only memory (EEPROM), Programmable Array Logic (PAL), a disk, an optical disc, a Digital Versatile Disc (DVD), and so on.

Claim 1:
A method for determining a set of service links for restoration of one or more service demands in case of one or more service link failures in a data communication network, wherein the data communication network comprises a plurality of vertices interconnected via at least one respective edge, and a service link is a path comprising at least two vertices and at least one edge which satisfies a respective service demand, the method comprising:
identifying a communications route cycle within the data communication network, the communications route cycle alternating through a set of vertices and a set of edges in a sequence of v<NUM>, e<NUM>, v<NUM>, e<NUM>, ..., vn, en, v<NUM>, wherein n is an integer greater than <NUM>, vi is a vertex on the communications route cycle, ei is a path between vi and vi+<NUM>, <NUM>≤i≤n, and vn+<NUM>=v<NUM>, wherein the set of vertices includes a plurality of vertices, each of the plurality of vertices corresponding to an end point of at least one service demand, wherein each of the one or more service demands is associated with the communications route cycle, wherein end points of each of the one or more service demands correspond to two vertices of the plurality of vertices, and wherein the identified communications route cycle is a shortest cycle of all possible cycles going through all end points of the one or more service demands;
identifying a path between a pair of vertices among the plurality of vertices, wherein the path is disjoint to the set of edges of the communications route cycle, wherein the identified path comprises at least one edge which is not comprised in the communications route cycle; and
determining the set of service links corresponding to the one or more service demands based on the identified path and communication route cycle, wherein each service link is a path in the data communication network.