WO2010036267A1 - Systèmes à redondances multiples dans un réseau optique - Google Patents

Systèmes à redondances multiples dans un réseau optique Download PDF

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Publication number
WO2010036267A1
WO2010036267A1 PCT/US2008/078029 US2008078029W WO2010036267A1 WO 2010036267 A1 WO2010036267 A1 WO 2010036267A1 US 2008078029 W US2008078029 W US 2008078029W WO 2010036267 A1 WO2010036267 A1 WO 2010036267A1
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WIPO (PCT)
Prior art keywords
path
protection
disjointness
working
priority
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PCT/US2008/078029
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English (en)
Inventor
Santosh Kumar Sadananda
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Dynamic Method Enterprises Limited
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Publication date
Application filed by Dynamic Method Enterprises Limited filed Critical Dynamic Method Enterprises Limited
Priority to CN200880000274A priority Critical patent/CN101743719A/zh
Priority to PCT/US2008/078029 priority patent/WO2010036267A1/fr
Publication of WO2010036267A1 publication Critical patent/WO2010036267A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L41/00—Arrangements for maintenance, administration or management of data switching networks, e.g. of packet switching networks
    • H04L41/06—Management of faults, events, alarms or notifications
    • H04L41/0654—Management of faults, events, alarms or notifications using network fault recovery
    • H04L41/0663—Performing the actions predefined by failover planning, e.g. switching to standby network elements
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0287—Protection in WDM systems
    • H04J14/0293—Optical channel protection
    • H04J14/0294—Dedicated protection at the optical channel (1+1)
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0287—Protection in WDM systems
    • H04J14/0293—Optical channel protection
    • H04J14/0295—Shared protection at the optical channel (1:1, n:m)
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0062—Network aspects
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0062—Network aspects
    • H04Q2011/0073—Provisions for forwarding or routing, e.g. lookup tables
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
    • H04Q11/0062—Network aspects
    • H04Q2011/0079—Operation or maintenance aspects
    • H04Q2011/0081—Fault tolerance; Redundancy; Recovery; Reconfigurability

Definitions

  • the present invention relates generally to the field of networking. More particularly, this invention relates to multiple redundancy schemes in an optical network and apparatus comprising same.
  • An optical network is a collection of optical network devices interconnected by links made up of optical fibers.
  • an optical network is a network in which the physical layer technology is fiber-optic cable. Cable trunks are interconnected with optical cross-connects (OXCs), and signals are added and dropped at optical add/drop multiplexers (OADMs).
  • OXCs optical cross-connects
  • OADMs optical add/drop multiplexers
  • the optical network devices that allow traffic to enter and/or exit the optical network are referred to as access nodes; in contrast, any optical network devices that do not are referred to as pass-thru nodes (an optical network need not have any pass-thru nodes).
  • Each optical link interconnects two optical network devices and typically includes an optical fiber to carry traffic in both directions. There may be multiple optical links between two optical network devices.
  • a given fiber can carry multiple communication channels simultaneously through a technique called wavelength division multiplexing (WDM), which is a form of frequency division multiplexing (FDM).
  • WDM wavelength division multiplexing
  • FDM frequency division multiplexing
  • each of multiple carrier wavelengths or, equivalently, frequencies or colors
  • TDM time division multiplex
  • a lightpath is a one-way path in an optical network for which the lambda does not change.
  • the optical nodes at which its path begins and ends are respectively called the source node and the destination node; the nodes (if any) on the lightpath in-between the source and destination nodes are called intermediate nodes.
  • An optical circuit is a bi-directional, end-to-end (between the access nodes providing the ingress to and egress from the optical network for the traffic carried b> that optical circuit) path through the optical network.
  • Each of the two directions of an optical circuit is made up of one or more lightpaths.
  • a single end-to-end end-to-end lightpath is provisioned for that direction (the source and destination nodes of that lightpath are access nodes of the optical network and are the same as the end nodes of the optical circuit).
  • the source and destination nodes of that lightpath are access nodes of the optical network and are the same as the end nodes of the optical circuit.
  • wavelength conversion is necessary and two or more lightpaths are provisioned for that direction of the end-to-end path of the optical circuit.
  • a lightpath comprises a lambda and a path (the series of optical nodes (and, of course, the interconnecting links) through which traffic is carried with that lambda).
  • LSPs are the circuits.
  • Each of these LSPs (uni-directional or bi-directional) form an end-to-end path where the generalized label(s) are the wavelength(s) of the lightpath(s) used.
  • the generalized label(s) are the wavelength(s) of the lightpath(s) used.
  • wavelength conversion is not used for a given bi-directional LSP, there will be a single end-to-end lightpath in each direction (and thus, a single wavelength; and thus, a single generalized label).
  • disjoint path is used to describe a relationship between a given path and certain other network resources (e.g., nodes, links, etc.).
  • network resources e.g., nodes, links, etc.
  • There are various levels of disjointness e.g., maximally link disjoint, fully link disjoint, maximally node disjoint, and fully node disjoint; and each can additionally be shared risk group (SRG) disjoint).
  • SRG shared risk group
  • Disjoint paths are formed for a variety of reasons, including forming restricted paths and protection paths. Restricted paths are formed to carry traffic that is not to travel through certain network resources for security reasons. Protection paths are used to provide redundancy; that is, they are used as alternate paths to working paths in case of a network failure of some kind. Protection paths are commonly implemented as either: 1) 1+1 protected; 2) 1 :1 protected; or 3) 1 :N mesh restored. A 1+1 or 1 : 1 protected path is a disjoint path from node A to node B in the network where one of the paths is a working path, and the other is a protection path. The working path and the protection path are typically established at the same time.
  • a mesh restored path from node A to node B is a pair of shared resource group disjoint paths in the network, where one of the routes is a working path and the other is a backup path.
  • the capacity dedicated on the backup path can be shared with backup paths of other mesh-restored lightpaths.
  • the paths are established and provisioned manually, for example, by a network administrator.
  • Protection schemes used in a conventional optical network assumes there is only one failure at a time.
  • a second path failure occurs before the first failed path recovers, particularly, in a 1 :N protection scheme
  • the traffic of the second failed path is dropped because the protection path is being used by the first failed path, until the network administrator can provision another path to take over the traffic of the second failed path.
  • an owner of an optical network typically has no discretion on how many working paths can share a 1 :N protection scheme.
  • a demand for a path with 1 :N protection is received, if there is no room for the 1 :N protection, the demand is dropped.
  • an apparatus such as a network access apparatus, comprising an access node, for coupling in a wavelength division multiplexing optical network, the apparatus including a database arrangement configured to store a representation of available paths from the access node to reachable destinations, the available paths including one or more working paths protected by one or more protection paths, and a routing means, such as a routing module or a routing device, arranged to receive a demand for a first protection path that meets a set of disjointness constraints with respect to a first working path according to a first protection scheme having a first priority, in response to the demand, locate from the database a second protection path that meets a second set of disjointness constraints with respect to a second working path according to a second protection scheme having a second priority, and assign the second protection path as a protection path to the first working path if the first priority of the first protection scheme is higher than the second priority of the second protection scheme.
  • a routing means such as a routing module or a routing device
  • an exemplary method includes receiving a demand for allocating a first protection path that meets a first set of disjointness constraints with respect to a first working path according to a first protection scheme having a first priority, in response to the demand, locating a second protection path that meets a second set of disjointness constraints with respect to a second working path according to a second protection scheme having a second priority, and assigning the second protection path as a protection path to the first working path if the first priority of the first protection scheme is higher than the second priority of the second protection scheme.
  • an apparatus such as a data network access apparatus, comprising an access node, for coupling in or with a wavelength division multiplexing optical network, the apparatus including, a database to store a representation of available paths from the access node to reachable destinations, the available paths including one or more working paths protected by one or more protection paths, and a routing module to receive a demand for a first protection path associated with a first working path according to a first protection scheme having a first priority, and preempt a second protection path associated with a second working path according to a second protection scheme having a second priority, if the first priority is higher than a second priority according to a protection scheme priority order specified by an owner of the network.
  • Figure 1 is a block diagram illustrating an exemplary access node according to certain embodiments of the invention.
  • Figures 2A and 2B are block diagrams of an exemplary database organization according to certain embodiments of the invention.
  • Figure 3 is a block diagram illustrating an example of a database organization according to anther embodiment of the invention.
  • Figure 4 is a block diagram illustrating an example of channel or wavelength statuses according to certain embodiments of the invention.
  • Figure 5 is a state diagram illustrating an example of operating state machines of channels according to one embodiment of the invention.
  • Figure 6 is a flow diagram illustrating an example of a process for handling a demand in an optical network node, according to one embodiment of the invention.
  • Figure 7 is a flow diagram illustrating an exemplary process for searching a working path according to one embodiment of the invention.
  • Figure 8 is a flow diagram illustrating an exemplary process for searching a 1+1 or 1 :1 protection path according to one embodiment of the invention.
  • Figure 9 is a flow diagram illustrating an exemplary process for searching a 1 :N protection path according to one embodiment of the invention.
  • Figure 10 is a flow diagram illustrating an exemplary process for handling path failures according to one embodiment of the invention.
  • Figure 11 is a flow diagram illustrating an exemplary process for handling a failure of a working path having a 1 :N protection according to one embodiment of the invention.
  • Figure 12 is a flow diagram illustrating an exemplary process for handling a failure of a 1 :N protection path according to one embodiment of the invention.
  • Figure 13 is a flow diagram of an exemplary process for handling a path failure having a 1+1 or 1 :1 protection scheme according to one embodiment of the invention.
  • Figure 14 is a flow diagram illustrating an exemplary process for handling a failure of a reroutable path according to one embodiment of the invention.
  • Figure 15 is a flow diagram illustrating an exemplary process for handling a recovery of a working path according to one embodiment of the invention.
  • Figure 16 is a block diagram illustrating an exemplary disjointness preference order and an exemplary protection scheme priority order, according to one embodiment of the invention.
  • Figure 17 is a flow diagram illustrating an exemplary process for handling a contention resolution according to one embodiment of the invention.
  • Figure 18 is a block diagram illustrating an exemplary process for rerouting a path that has been preempted by a contention resolution, according to one embodiment of the invention.
  • references in the specification to "one embodiment' * , "an embodiment”, “an example embodiment”, etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.
  • Coupled may mean that two or more elements are in direct contact with each other (e.g., physically, electrically, optically, etc.).
  • Coupled may mean that two or more elements are in direct contact (physically, electrically, optically, etc.). However, “coupled” may also mean that two or more elements are not in direct contact with each other, but yet still co-operate or interact with each other.
  • each of the working paths sharing a protection path is associated with a priority. No more than one working path having the same priority may share a protection path.
  • the priorities of the working paths may be used to determine which working path claims the protection path when multiple working paths fail. A failed working path with higher priority claims the protection path, while the failed working path with lower priority is reallocated with another path.
  • a service provider or a network owner is provided with a capability to assign a preference order of disjointness and a priority order of protection scheme.
  • the preference order and protection scheme priority order may be used in a contention resolution process of paths, where for a particular service level an appropriate protection scheme demanded cannot be allocated.
  • an existing path,- wavelength combination with priority lower than the one in demand may be preempted and rerouted based on the disjointness preference order and the protection scheme priority order,
  • a path is a series of nodes and interconnecting links.
  • a lightpath is a path/wavelength combination (also referred to as path/wavelength or lambda, or channel).
  • a bidirectional optical circuit has a path (where there is more than one lightpath in a given direction, it is the concatenation of the paths of these lightpaths).
  • a working or protection path is made up of one or more lightpaths (e.g., a bidirectional working or protection path is a type of bidrectional optical circuit, whereas a unidirectional working path that is conversion free is made up of one lightpath).
  • a database is built and maintained that stores available paths from a source node to reachable destination nodes in a network in which the links between nodes can carry multiple channels.
  • Each of the available paths being a series of nodes and interconnecting links from the source node to one of the reachable destination nodes.
  • the paths are stored in said database grouped by common destination nodes, there is a cost stored with each of the paths, and/ or the paths are sorted.
  • there is a cost stored with each of the paths the paths are grouped by common destination node, and the paths in a group are sorted at least in part by their cost.
  • each of the available paths has associated to it in the database a set of one or more of the channels on the interconnecting links available to form path/channel combinations (in a WDM network, these path/channel combinations would be path/wavelength combinations).
  • each channel or path/wavelength may include status of that channel, such as, for example, the protection scheme, the priority of the channel for the 1 :N protection, etc.
  • the invention is not limited to WDM network, the invention will be described with reference to WDM networks for illustrative purposes.
  • WDM networks for illustrative purposes.
  • Such a database may be built, maintained, structured, used, etc. in a variety of ways; exemplary ones of which are described herein.
  • a database that stores available paths from a source node to reachable destination nodes is used for handling one or more channel failures.
  • a path is selected from the database based on its destination. Following the selection of the path, a wavelength available on that path is selected from the database, hi certain embodiments of the invention, such paths are paths that meet a set of disjointness constraints (e.g., maximally link disjoint, fully link disjoint, maximally node disjoint, fully node disjoint, as well as optionally shared risk group disjoint) selected through the determination of intersection sets of the network resources (e.g., nodes and/or links) of available paths in the database.
  • disjointness constraints e.g., maximally link disjoint, fully link disjoint, maximally node disjoint, fully node disjoint, as well as optionally shared risk group disjoint
  • Figure 1 is a block diagram illustrating an exemplary access node according to certain embodiments of the invention. While Figure 1 illustrates an access node for use in a source based scheme, the invention is not so limited.
  • the exemplary node shown in Figure 1 may be implemented within a control plane, a data plane, or a combination of both the control and data planes of a node.
  • the exemplary node 100 includes, but not limited to, one or more node databases 101 , a connection manager 102, and one or more node modules 103.
  • the node databases 101 include a connectivity database 105 (also referred to as a routing database), a link state database 107, and a network owner preference database 104.
  • the node databases 101 may be implemented as multiple databases linked with each other. Alternatively, databases 101 may be implemented as a centralized database globally managed by, for example, database module 108. In addition, portions or all of the information stored in each database may be duplicated and stored in a local database accessible by one or more modules of the node modules 103. Other configurations apparent to those with ordinary skill in the art may exist.
  • the network owner preference database 104 includes a set of information concerning the preferences that a network owner or a service provider may have regarding operations of the network or the respective node. For example, according to one embodiment, the preference database 104 may include, among others, the number of working paths that can share a 1 :N protection path.
  • the preference database 104 may further include the protection scheme priority order that the network owner or the service provider may prefer during an allocation or a contention resolution of a protection path, w r hen a protection path demanded cannot be allocated at a given time.
  • An example of the protection scheme priority order is shown in Figure 16 and the embodiments of contention resolution schemes are described in details further below,
  • the link state database 107 includes a set of one or more link state structures (not shown), one for each link connected to that node. While in certain embodiments these links are discovered through a link management protocol (e.g., a link protocol module), alternative embodiments could use other techniques.
  • each link state structure records a neighboring node, a port through which that neighboring node is connected (fiber links end up at a port on the node), and available wavelengths on that link (through the port).
  • the connectivity database 105 includes a set of one or more structures to store the available paths.
  • the connectivity database 105 may also store the configuration of the cross connect of the node. Exemplary embodiments of the connectivity database 105 are illustrated in Figures 2A and 2B.
  • signaling database 106 includes a set of information, including, but not limited to, the working path and protection path pairs and optionally their respective status. An exemplary embodiment of the signaling database 106 is shown in Figure 3.
  • the node modules 109 include, but not limited to, a database module 108, a set of one or more routing modules 109. a signaling module 110, and a link protocol module 1 11.
  • the routing modules 109 include, but not limited to, a demand module 112, a path selection module 113 (which may include a regular path module 1 14 and protection path module 115), an allocate, deallocate module 1 16. and an add remove module 117. It will be appreciated that other modules, such as, for example, a protection module, etc.. may be included.
  • the database module 108 builds and maintains one or more databases 101. such as, for example, connectivity database 105. There are a variety of techniques for doing so, exemplary ones of which are described later herein.
  • the demand module 112 receives demands for new path/wavelength combinations and invokes the path selection module 113 and allocate module 1 16 to service the demand.
  • the path selection module 870 includes a regular path module 114 and a disjoint path module 115.
  • the path selection module 113 receives requests for paths and the path selection criteria and invokes the appropriate one(s) of the regular path module 114 and disjoint path model 115 for selecting a regular path (e.g., a working path) and ; or a protection path respectively.
  • the allocate module 116 causes the selected path/wavelength combinations to be allocated (e.g., the access node's cross connect and connectivity/routing database 105, as well as, in certain embodiments, communication to other nodes), while the deallocate module causes path/wavelength combinations to be deallocated.
  • the add/remove module 117 addresses additions and removals of channels, links, and nodes in the optical network.
  • the protection module (not shown) is called responsive to the add/remove module 1 17 to implement a redundancy scheme.
  • signaling module 110 is responsible for signaling the nodes along a path indicating the path is up or down. For example, when a demand for a path is issued, the signaling module 110 receives such a demand. Signaling module 1 10 may pass the demand to the routing modules 109 to request a working path and optionally a protection path associated with the work path. In response to the demand, the routing modules 109 may, for example, via path selection module 1 13 and/ or allocate module 116, access the connectivity/routing database 105 to select a working path and/or a protection path for the demand, hi one embodiment, the demand may include a protection scheme demanded, such as, for example, 1- ⁇ -1.
  • the demand may further include a priority of a working path demanded if the demand demands for 1 :N protection.
  • the priority may be assigned by the node (e.g.. signaling module or LMP module), for example, in a first-come- first-serve manner.
  • the routing modules 109 may allocate a working path and a protection path based on this information, [0051] If a protection path demanded cannot be allocated, according to one embodiment, the routing modules 109 may optionally perform contention resolution based on a disjointness preference order and a protection scheme priority order, for example, a lower disjointness, based on a preference order stored in the preference database 104, which may preempt an existing allocated path. The preempted existing path may then be rerouted according to one or more routing policies.
  • the disjointness preference order and the protection scheme priority order may be set up or specified by an owner of the network.
  • the routing modules 109 pass the path allocation information to the signaling module 110. which in turn signals the nodes associated with allocated path. Once the nodes of the path have been signaled, the traffic of the path may occur. Once the paths have been allocated and signaled, the routing modules 109 may update the connectivity/routing database 105 reflecting the path allocations (as shown in Figures 2A and 2B), while signaling module 110 may also update the corresponding signaling database 106 (as shown in Figure 3).
  • connection manager 102 is responsible for managing the connections of the node.
  • Connection manager 102 typically communicates with the hardware of the nodes (e.g., physical layers of the network stack or a data plane).
  • Connection manager 102 communicates with node modules 103 and may access one or more databases 101.
  • Communication manager 102 may communicate with the hardware via one or more device drivers of an operating system, such as, for example, Linux or other operating systems.
  • the node databases 101 may be built and maintained, and the paths may be established and provisioned using a variety of techniques. According to one embodiment, the node databases 101 and the paths may be established and provisioned dynamically using sendee level topologies, which detailed information may be found in a co-pending U.S. Patent Application No. 10/754,931, filed January 9, 2004, entitled "A Method and Apparatus for a Network Database in an Optical Network", and assigned to a common assignee of the present application. The above- identified U.S. patent application is hereby incorporated by reference.
  • Figures 2A and 2B illustrate two exemplary connecth it> /routing database(s) organizations according to embodiments of the invention.
  • Figure 2 A is a block diagram of an exemplary database organization according to one embodiment of the invention.
  • Figure 2A illustrates a destinations structure 201 and representation of the possible end-to-end paths 202.
  • the destinations structure 201 having entries destination 203 A to 2031, is to store each of the reachable destinations in a single entry.
  • Each of the destination entries 203A to 2031 is associated with the available paths to that destination 204A to 2041.
  • the destination 203A has associated to it paths 205A-205I. In other words, the available paths are grouped by common destinations.
  • Each path has associated to it its path channel set; paths 205A-205I respectively have path channel sets 206A-206I.
  • Each of these path channel sets 206A-206I includes a set one or more lambdas (e.g., path channel set 206A includes lambdas 207A-207I; path channel set 2061 includes lambdas 208A-208I).
  • each path has a path cost and a path status.
  • the path costs are to identify the relative costs of the paths so that they may be distinguished for shortest path purposes. It should be noted that this cost is on a per path basis, as opposed to a per path/wavelength combination basis.
  • the path status identifies the status of the path (e.g., up, down, etc. - where up means that the path is usable and down means that the path is currently not usable (e.g., a path may have a status down if one or more links in the path has been removed).
  • each lambda has stored with it a lambda status. The lambda status may not be limited to being allocated or unallocated.
  • a lambda that has failed due to a fiber cut or laser failure could be assigned a status of "broken".
  • the granularity for tracking allocated/unallocated status is simply the lambda level.
  • the granularity of allocated/unallocated status is a status for each direction for each lambda.
  • each lambda may also include: 1 ) for a path/wavelength combination used for a 1 :N protection path, the number of the working paths currently sharing the 1 :N protection, the priorities of the working paths currently sharing the 1 :N protection; and 2) for a path wavelength combination used for a working path, the priority of that working path.
  • An example of the lambda status embodiments is illustrated in Figure 4.
  • the paths for each destination are also sorted by a set of one or more path characteristics (e.g., any available wavelengths, number of available wavelengths, the cost, load balancing issues, etc.). As a result, depending on the sort, the next path to select for allocation to a given destination will more likely be at the beginning of the group. Once a path is selected, the available wavelengths on that path and their status can be accessed for selection therefrom. In certain embodiments of the invention, the wavelengths of a path channel set are sorted by lambda status so that the next unallocated lambda to select more likely at the beginning of the set.
  • path characteristics e.g., any available wavelengths, number of available wavelengths, the cost, load balancing issues, etc.
  • the destinations structure 201 could be stored as a separate structure (e.g., a linked list, a tree, etc.), each entry of which includes a pointer to a structure (e.g., a linked list, a tree, etc.) for each group of paths; each entry for the path group structure could include a pointer to a structure (e.g., a linked list, a set, etc.) for the path channel set of that path.
  • a separate structure e.g., a linked list, a tree, etc.
  • each entry of which includes a pointer to a structure e.g., a linked list, a tree, etc.
  • each entry for the path group structure could include a pointer to a structure (e.g., a linked list, a set, etc.) for the path channel set of that path.
  • Figure 2A illustrates an exemplary database organization
  • alternative embodiments of the invention could have different organizations and structures.
  • the paths could be grouped through the sorting of a table having each path as an entry; rather than having a separate lambdas structure for each path, the available lambdas could be stored along with the path.
  • certain information is stored along with the paths and lambdas (cost and status)
  • alternative embodiments could store more, less, and/or different information.
  • the lambdas in the path channel sets are sorted
  • alternative embodiments of the invention may rely on searching an unsorted path channel set.
  • certain embodiments of the invention sort the paths by cost and whether there are any unallocated channels thereon
  • alternative embodiments of the invention may sort the paths in the groups by cost but not by whether there are any unallocated channels; such embodiments would rely on searching to locate the lowest cost path with an unallocated channel.
  • FIG. 2B is a block diagram illustrating an example of database organizations according to another embodiment of the invention.
  • the exemplary database 250 may be implemented within a connectivity routing database, such as, connectivity database 105 of Figure L accessed and maintained by routing modules 109.
  • the database 250 maybe implemented across multiple databases, such as, connectivity database 105, signaling database 106, and/or link state database 107, etc.
  • portions or all of the information of database 250 may be duplicated at each of the databases, such as those shown in Figure 1.
  • exemplary database 250 may be implemented as possible end-to-end paths 202 of a variety of destinations as shown in Figure 1.
  • the database 250 is organized based on the possible end-to-end paths, hi one embodiment, the database 250 includes, but is not limited to, the fields of path 251, the lambda of the path 252 (e.g., wavelength or lambda), lambda status 253, the number of the working paths currently sharing a 1:N protection 254 (if the path/wavelength combination is being used for a 1 :N protection path), the priority of the path 255 (if it is a working path currently sharing 1 :N protection), priorities of the working paths currently sharing the 1 :N protection 256 (if it is a 1 :N protection path), and other fields 257 apparent to those with ordinary skill in the art.
  • the fields of path 251 the lambda of the path 252 (e.g., wavelength or lambda), lambda status 253, the number of the working paths currently sharing a 1:N protection 254 (if the path/wavelength combination is being used for a 1 :N protection path), the priority of the path 255 (if it is a working
  • the database was organized by indexing all the paths managed by the respective node.
  • the field 251 is used to list one or more paths to a destination node. As described above, each path may include multiple channels (e.g., lambdas or wavelength in a WDM optical network).
  • Field 252 is used to specify a channel on the path indicated by field 251. In a WDM optical network, fields 251 and 252 may be used to specify a path and wavelength combination (e.g., a lambda). For the purposes of illustrations, a path and wavelength combination may be referred to as path/wavelength or path/channel.
  • pathLlambdal indicates as a path having lambdal (e.g., a wavelength having a frequency of lambdal) within path 1 from a source node to a destination node.
  • lambdal e.g., a wavelength having a frequency of lambdal
  • Lambda status field 253 may be used to specify the current status of the path/lambda combination (e.g., path/wavelength combination).
  • lambda status field 253 may include at least one of the lambda statuses shown in Figure 4, which will be described in details further below.
  • the lambda status field 253 may also be used to indicate the type of the respective path-lambda combination.
  • path 258 is a path 1 -'lambda 1 combination and it is also an allocated working path having a status of allocated/working.
  • Path 259 is a pathl/l ⁇ mbda2 combination and it is an unallocated path having a status of unallocated, which may be subsequently allocated as a working path or a protection path.
  • the count of 1 :N protection field 254 may be used to indicate the number of working paths currently sharing the 1 :N protection path (where the path/wavelength combination is being used for that purpose).
  • a 1 :N protection path may be used by a predetermined number of working paths, which may be specified by a network owner or a service provider, hi one embodiment, the maximum number of working paths that may share a 1 :N protection path may be specified in a network owner or service provider preference database, such as, for example, preference database 104 of Figure 1. That is, a network owner or service provider may specify during the configuration or at real-time the maximum number of the working paths that are allowed to share the same 1 :N protection. In one embodiment, the maximum number of working paths that may share a 1 :N protection is six.
  • the demand when a demand for a working path with a 1 :N protection is received, the demand may include a priority of a working path in demand with 1 :N protection.
  • the priority may be assigned by the network according to one or more policies, such as, for example, a first-come-first-serve manner. According to one embodiment, no more than one of the working paths having the same priority would be allowed to share the same 1 :N protection path.
  • the priority of the working path field 255 may be used to store the priority of that working path.
  • the priority of the working paths may be used to determine which working path would obtain the 1 :N protection path.
  • the working path with higher priority will obtain the 1 :N protection path while the one with lower priority may be allocated with a new path or rerouted.
  • the maximum number of working paths may vary. For example, for higher 1 :N protection, the maximum number of working paths that can share the 1 :N protection may be lower, while the cost to maintain such a configuration may be higher. Likewise, for lower 1 :N T protection, the maximum number of working paths that can share the 1 :N protection may be higher, while the cost to maintain such a configuration may be lower.
  • the network owner or service provider When configuring a network, according to one embodiment, the network owner or service provider is provided an opportunity to specify number of the working paths that can share a 1 :N protection. The network owner or service provider may balance the considerations of the protection level and the cost to maintain such a protection level of a network when configuring the network.
  • the exemplary database 250 further includes a field 256 for a 1 :N protection path to store the priorities of the working paths currently sharing with the respective 1 :N protection path. Field 256 may be used by a 1 :N protection path to indicate the priorities of the working paths currently sharing the 1 :N protection path.
  • path 265 is a 1 :N protection path that are currently shared with three working paths: path 258 having a priority of 2, path 260 having a priority of 3, and path 263 having a priority of 5.
  • the number of the working paths currently sharing the 1 :N protection path 265 is indicated in the respective field 254.
  • the priorities of the working paths 258, 260, and 263 are indicated in the respective field 256.
  • the count of the 1 :N protection stored in the field 254 may be used to determine whether the respective 1 :N protection path may be shared with an additional working path.
  • the 1 :N protection path 265 currently has three working paths sharing with it, if the maximum number of working paths that can share with one 1 :N protection is three, which may be specified in a network owner or service provider preference database 104 of Figure 1, when a new demand for a 1 :N protection is received, the current 1 :N protection path 265 may not be assigned to the new demand because its count of working paths currently sharing (e.g., three as indicated in field 254) has reached the maximum limit.
  • the priorities of the working paths 258, 260, and 263 stored in the field 256 may be used to determine whether the respective 1 :N protection can be shared with an additional working path having a specific priority. Since no more than one working path having the same priority can share the same 1 :N protection path, the field 256 may be used to determine whether the 1 :N protection has already a working path that has the same priority as the one in demand, and if so, the 1:N protection path cannot be allocated to the demand.
  • the 1 :N protection path 265 is shared with three working paths (e.g., working paths 258, 260» and 263) having priorities of 2, 3, and 5. If a new demand having a priority of 2 is received, the field 254 is checked whether number of the working paths currently supported by the 1 :N protection path 265 has reached the maximum number. It is assumed that the maximum number of the working paths that can share a 1 :N protection path is six. Since the number of the working paths currently sharing the 1 :N protection path 265 is three as indicated in field 254, the field 256 is then checked whether the 1 :N protection path 265 is already supporting a working path having the same priority of the demand.
  • three working paths e.g., working paths 258, 260» and 263 having priorities of 2, 3, and 5.
  • the 1 :N protection path 265 is already supporting a working path having the same priority of 2 (e.g., working path 258). As a result, the 1 :N protection path 265 cannot be shared by the demand, and another or a new 1 :N protection path may be allocated for the demand.
  • FIG. 3 is a block diagram illustrating an example of a database organization of a signaling database according to one embodiment of the invention.
  • the exemplary database 300 may be implemented as part of a signaling database, such as, signaling database 106 of Figure 1.
  • the exemplary database 300 may be implemented across multiple databases, such as, connectivity/routing database 105, signaling database 106, link state database 107, etc. Portions or all of the information stored in database 300 maybe duplicated in other databases.
  • exemplary database 300 includes, but not limited to, working path field 301, protection path field 302, and the priority of the working path field 303 if the working path is in a 1 :N protection.
  • the working path field 301 is used to store an identity of a working path and the protection path field 302 is used to store an identity of a protection path associated with the working path identified by field 301. If the protection scheme for the working path is a 1 :N protection, the field 303 is used to store a priority of the working path identified by the working path field 301.
  • record 304 includes a working path pathl/lambdal stored in the respective field 301 and a protection path pathn/lambda2 stored in the respective field 302.
  • the priority of the working path is indicated in the field 303 as 2, which also indicates the protection scheme is a 1 :N protection scheme.
  • the protection scheme (e.g., 1 :1, 1-1 , etc.) may also be determined based on the status of the protection path pathn/lambda2 from other databases, such as. protection path 265 shown in Figure 2B.
  • the exemplary database 300 may be accessed and maintained by a signaling module, such as signaling module 110 of Figure 1. However, it is not so limited.
  • the database 300 may also be accessed by other modules, such as those shown in Figure 1.
  • the database 300 may be used by the signaling module to determine how to handle the traffic of the failed paths.
  • the signaling module may be notified of the failure by the connection manager (e.g., connection manager 102 of Figure 1).
  • the signaling module may determine the protection path corresponding to the failed working path.
  • the protection path for the working path pathl.'lambdal is pathn/lambda2 indicated by the respective field 302.
  • the signaling module may switch the traffic of the failed working path (e.g., path pathl /lambda 1) to its protection path (e.g., path ⁇ athn/lambda2) and signal the nodes associated with the protection path to notify them that the traffic has been switched over to the protection path.
  • the signaling module may notify the connectivity/routing database (e.g., database 105 of Figure 1) to update the status of the working path and the protection path.
  • the connectivity/routing database e.g., database 105 of Figure 1
  • the status of failed working path pathl/lambdal may be changed from allocated/working to broken and the status of the protection path pathn/lambda2 may be updated from allocated/protection/ 1 :N to allocated/protection/ 1 :N/used, which may be reflected in the databases shown in Figures 2 A and 2B.
  • Other information or databases may also be updated.
  • the priority of a working path indicated in field 303 may be used to determine which failed working path gets the 1 :N protection path.
  • the working path having higher priority may get the 1 :N protection path, while the traffic of the working path having lower priority may be rerouted according to one or more policies.
  • the signaling module switches the traffic of path2,1ambda2 to its corresponding protection path pathn/lambda2 and notifies the connectivity/ routing database (e.g., databases 200 or 250 shown in Figures 2A and 2B).
  • the status of the working path path2 ⁇ larnbda2 may be changed from allocated working to broken and the status of the protection path pathii- Iambda2 may be changed from allocated/protection/' 1 :N to allocated/protection/ 1 :N/used in databases 200 and 250 of Figures 2A and 2B.
  • the signaling module may compare the priorities of two failed working paths (e.g., pathl /lambda 1 and path2'lambda2) and determine which working path gets the protection path (e.g., pathn/lambda2).
  • the second failed working path pathl/lambdal of record 304 has a higher priority (e.g., priority of 2) than the priority of the first failed working path path2/lambdal (e.g., priority of 3).
  • the second failed working path will get the 1 :N protection path pathn/lambda2 and the traffic currently on the protection path pathn/lambda2 for the first failed working path (e.g., path2/lambdal) may be rerouted.
  • a new working path and/or a new protection path may be allocated for the first failed working path (e.g., path2/tambdal).
  • the signaling module may check whether the failed working path has recovered. If so, the traffic of the failed protection may be switched back to the recovered working path and optionally a new protection path may be allocated.
  • the traffic of the corresponding protection path on behalf of the broken working path may be switched immediately back to the recovered working path.
  • the status of the recovered working path may be changed from broken to allocated/working and the status of the protection path may be changed from allocated/protection/l:l or l:N/used to allocated/protection/ 1 : 1 or 1 :N.
  • the recovered working path may be released back to the unallocated pool and its status may be changed from broken to unallocated.
  • the protection path that takes over the traffic for the failed and now recovered working path may act as a working path.
  • the status of the protection path taking over may be changed from allocated/protection to allocated working.
  • a new protection path may be allocated for the newly converted working path.
  • Other operations or configurations exist and are within the scope of the invention. Exemplary Channel Status/States Embodiments
  • the channel or wavelength (lambda) statuses may be stored in one or more databases, such as databases shown Figures 2A-2B and 3.
  • the channel or wavelength statuses may be used when establishing a working path, a protection path, and/or alternatively, for handling one or more path failures.
  • Figure 4 is a block diagram illustrating an example of channel or wavelength statuses according to certain embodiments of the invention.
  • the exemplary channel statuses 400 includes, but not limited to. unallocated status 401, allocated status 402, and broken status 403.
  • the statuses 400 may be used in a variety of optical networks, for the purposes of illustrations, a WDM optical network is used as an example throughout this application.
  • the embodiments described herein are not limited to WDM optical networks. They may be applied to other types of networks.
  • a channel path/wavelength in a WDM optical network
  • the channel is free to be allocated to any new demand, either as a working path or a protection path.
  • the respective channel or path/' wavelength combination may be marked as broken (e.g., having a broken status 403).
  • a path When a path is allocated, it may be allocated as a working path having an allocated/working status 404 or a protection path having an allocated/protection status 405.
  • a path maybe allocated as a protection path having a 1+1 protection scheme with an allocated/protection' I 4 T status 406, a protection path having a 1:1 protection scheme with an allocated'protection/1 :1 status 407, or a protection path having a 1 :N protection scheme with an allocated' protection/I :N status 408.
  • the 1 : 1 and 1:N protection path e.g.. allocated'protection/l: l status 408 and allocated protection/' 1 :N status 407 may be in use, when the protection path takes over the traffic of its corresponding working path. In such case, the status of the respective protection path may be referred to as allocated protection!
  • the status of the failed or broken working path may be referred to as broken status 403. Otherwise, when the working path is still up, its protection path status ma) be referred to as allocated/protection 1 : 1 or 1 :N unused or simply allocated/protection/ 1 :1 or 1 :N, because it is not being used. [0090) Furthermore, when a path is allocated, either as a working path or a protection path, the allocated path may be temporarily marked as reserved (not shown). This status may be used when a path is allocated, but waiting for the signaling module to signal the nodes of the allocated paths and return the status of whether the signaling operations are successful.
  • Figure 5 is a state diagram illustrating an example of operating state machines of channels according to one embodiment of the invention.
  • the exemplary state machines 500 include, but not limited to, an unallocated state 501, an allocated state 502, a broken state 503, and a reserved state 504.
  • a channel or path/wavelength combination is in the unallocated state 501 when the corresponding channel has not been allocated to any demand.
  • the allocated channel When a path/wavelength combination is allocated, either as a working path, a protection path, or a reroutable path, the allocated channel is in the allocated state 502. When a path/wavelength combination is broken, either from unallocated state 501, allocated state 502, or reserved state 504, it is in broken state 503. When a path/wavelength combination is allocated, but waiting for a confirmation whether the signaling has been performed successfully, the path/wavelength combination is in the reserved state 504.
  • a path/ wavelength combination can transition from one state to another of the states 501-504 dependent upon certain events, which may occur locally within the node or between the nodes in the network.
  • local events occur at the node when something happens. For example, some local events occur when a link or a channel fails, or alternatively, when a demand is received. According to one embodiment, some of the local events may be defined as follows:
  • the network events are transmitted among some nodes of the network and some of the network events may be defined as follows:
  • some events may occur both locally and in the network.
  • Some of the local and network events may be defined as follows:
  • the channel may have unallocated status 401.
  • the channel may have broken status 403.
  • the channel may have allocated statuses 404-408, either as a working path or a protection path.
  • the channel may have allocated statuses 404-408 with a reserved indication. Other configurations may exist.
  • FIG. 6 is a flow diagram illustrating an example of a process for handling a demand in an optical network node, according to one embodiment of the invention.
  • the exemplary process 600 may be performed by a processing logic that may comprise hardware (circuitry, dedicated logic, etc.), software (such as is run on a dedicated machine), or a combination of both.
  • a demand for a path is received at a node, such as, for example, a source node of an optical circuit.
  • the demand includes a protection scheme, such as, for example, a 1 + 1 , 1 :1, 1 :N or reroutable scheme. If the protection scheme demanded is a 1 :N protection scheme, according to one embodiment, the demand may further include a priority of the working path in demand (e.g., to determine which working path gets the 1 :N protection path when multiple working failures occur subsequently). In an alternative embodiment or where the demand does not include a priority, the priority of the demand may be assigned by the node based on one or more policies.
  • the priority of the demand may be assigned by the node on a first-come- first-served basis.
  • the first demand would be assigned with a priority of one and the second demand would receive a priority of two, etc.
  • priorities may be assigned randomly.
  • a working path is selected from a set of available paths to the destination in demand that has one or more unallocated channel (e.g., path/wavelength combination).
  • a WDM network is used herein to describe the embodiments of the present application.
  • the selection is based on the destination of the demand. For example, the selection is performed by walking through a database based on the destination, such as, for example, exemplary database 200 shown in Figure 2 A, until an unallocated path that leads to the destination of the demand is located.
  • the selection may be performed by locating a path that is unallocated based on a database, such as, for example, exemplary database 250 of Figure 2B.
  • the selection may be performed by walking through the paths shown in field 251 to search for a path that has not been allocated, such as, for example, path 259.
  • a path that has not been allocated such as, for example, path 259.
  • a protection path is searched from a set of available paths to the destination that satisfies the set of disjointness constraints with respect to the working path selected above.
  • the search may be conducted based on node disjointness with respect to the working path selected above.
  • the search may be conducted based on a disjointness preference order set up by a network owner or a service provider, such as, for example, in preference database 104 of Figure 1. Further detailed information concerning selecting a protection path will be described further below.
  • a contention resolution may be performed.
  • another path having lower priority protection scheme than the one in demand may be searched and preempted (e.g., bumped).
  • the path preempted is then allocated as a protection path and the working path and the traffic of the preempted path may be rerouted.
  • the exemplary contention resolution will be described in details further below. If the contention resolution cannot be resolved, the demand may be dropped and the already allocated resources (e.g., the allocated working path) may be released.
  • the working path and the protection path are allocated to the demand and at block 604, the associated databases, such as, for example, databases shown in Figures 2A-2B and 3, may be updated.
  • the status of the working path may be changed from unallocated to allocated/working and the status of the protection path may be changed from unallocated to allocated/ protection/1+1, 1:1, or 1 :N.
  • the nodes of the path are signaled by, for example, signaling module 110 of Figure 1.
  • the state of the paths may be in a temporary state, such as reserved state 504 of Figure 5, from unallocated state 501.
  • the status of the paths may still be maintained as allocated/working and allocated/protection' 1+1, 1 ; 1, or 1 :N with a reserved mark or label, which may be implemented as an additional field in the exemplary databases shown in Figures 2A-2B and 3 (not shown).
  • the paths may be changed from reserved state to permanent state.
  • the state of the paths may be changed from reserved state 503 to allocated state 502 via an allocate update event.
  • the reserved label associated with the status of the paths may be removed to indicate that the paths have been allocated permanently. If the signaling has not been performed successfully, the state of the paths may be changed from reserved back to unallocated via a failed event.
  • the state of the paths may be changed from reserved state 504 to broken state 503, via a failure event or a broken event.
  • the status of the paths may also be changed.
  • the status of the failed path may be changed from allocated/working or allocated/ protection/' 1 + 1 , 1 : 1 , or 1 :N to broken.
  • the exemplary process 600 of Figure 6 may be performed again for searching for a path that is suitable for replacing the failed path. Other operations may also be performed.
  • FIG. 7 is a flow diagram illustrating an exemplary process for searching a working path according to one embodiment of the invention.
  • the exemplary process 700 may be performed by a processing logic that may comprise hardware (circuitry, dedicated logic, etc.), software (such as is run on a dedicated machine), or a combination of both.
  • exemplary process 700 may be performed as a part of operations in block 602 of Figure 6.
  • exemplary process 700 may be invoked in response to a demand for a working path or rerouting a working path.
  • a demand for a working path is received. If it is for a 1 :N protection scheme, the demand may also include a priority of the working path being searched.
  • a path is selected from a set of available paths to the destination in demand that have one or more unallocated path/wavelength combination. The search may be performed based on the exemplary database organization illustrated in Figure 2A or Figure 2B as described above.
  • the selected path is allocated to the demand.
  • the associated databases such as those exemplar ⁇ ' databases shown in Figures 2A-2B and 3 may be updated with respect to the allocated working path.
  • FIG. 8 is a flow diagram illustrating an exemplary process for searching a 1-t-l or 1 :1 protection path according to one embodiment of the invention.
  • the exemplary process 800 may be performed by a processing logic that may comprise hardware (circuitry, dedicated logic, etc.), software (such as is run on a dedicated machine), or a combination of both.
  • the exemplary process 800 may be performed as a part of the operations involved at block 603 of Figure 6.
  • exemplary process 800 may be invoked in response to a demand for a 1 -r 1 or 1 : 1 protection path or rerouting a 1+1 or 1:1 protection path.
  • a demand for searching a protection path is received.
  • the demand may include a protection scheme type (e.g., 1+1 or 1:1).
  • a path e.g., path/wavelength combination
  • the search may be performed based on a disjointness preference order specified by a network owner or a sendee provider, which may be stored in the exemplary preference database 104 of Figure 1.
  • the search may be performed based on the databases organizations as shown in Figures 2A-2B and 3 as described above.
  • the selected path is then allocated to the demand at block 803.
  • the associated databases such as, for example, the exemplary databases shown in Figures 1, 2A-2B, and 3, may be updated with respect to the newly allocated protection path.
  • the status of the newly allocated protection path may be updated from unallocated to allocated/protection/1+1 or 1:1.
  • the operations of block 804 may be a part of operations of block 604 of Figure 6. Other operations apparent to those with ordinary skill in the art may be performed.
  • FIG. 9 is a flow diagram illustrating an exemplary process for searching a 1:N protection path according to one embodiment of the invention.
  • the exemplary process 900 may be performed by a processing logic that may comprise hardware (circuitry, dedicated logic, etc.), software (such as is run on a dedicated machine), or a combination of both.
  • the exemplary process 900 may be performed as a part of the operations involved at block 603 of Figure 6.
  • exemplary process 900 may be invoked in response to a demand for a 1 :N protection path or rerouting a 1 :N protection path.
  • a path (e.g., path/wavelength combination) is selected from a set of available paths leading to the destination in demand that satisfies the set of disjointness constraints and has already been allocated as a 1 :N protection path for other demands or working paths.
  • the search may be performed based on a disjointness preference order specified by a network owner or a service provider, which may be stored in the exemplary preference database 104 of Figure 1.
  • the search may be performed based on the databases organizations as shown in Figures 2A-2B and 3 as described above.
  • each 1 :N protection path may be shared by up to a maximum number of working paths, which maybe specified by a network owner or service provider in the preference database, such as database 104 of Figure 1.
  • some databases such as connectivity/routing database 105 and signaling database 106, may store information regarding how many working paths currently sharing a specific 1 :N protection path, as illustrated in Figures 2A-2B and 3 and described above.
  • the count of the 1 :N protection which may be stored in field 254 of Figure 2B, maybe examined whether it is greater than or equals to the maximum limit of 1 :N protection which may be stored in the preference database 104 of Figure 1.
  • the instant 1 :N protection path is then allocated as a 1 :N protection path for the working path in demand.
  • the associated databases such as those shown in Figures 1. 2A-2B, and 3, may be updated with respect to the newly allocated 1 :N protection path.
  • the status of the 1 :N protection path remains unchanged (e.g., allocated/protection/ 1 :N) since the protection path has been allocated to other working paths prior to the current working path in demand.
  • the count of the 1 :N protection for example, stored in field 254 of Figure 2B, may be updated as count - count + 1.
  • the priority of the working path in demand may be added to the priorities of the working paths currently sharing with the 1 :N protection path, such as, for example, field 256 of Figure 2B.
  • a new 1 :N protection path is searched.
  • the search may be performed by locating an unallocated path that satisfies the disjointness constraints with respect to the working path in demand.
  • the newly found 1 :N protection path is allocated to the demand.
  • the associated databases such as those shown in Figure 1, 2A-2B, and 3, may be updated for the new allocation.
  • the status of the newly allocated 1 :N protection path may be updated from unallocated to allocated/protection/ 1 :N.
  • the priority of the working path associated with he newly allocated 1 :N protection path may be added to the priorities of the working paths currently sharing the 1 :N protection path, which may be stored in field 256 of Figure 2B.
  • the demand may be dropped.
  • a contention resolution may be performed. The contention resolution will be described further in detail below, for example, in Figures 17 and 18 and their respective descriptions.
  • the operations of blocks 906 and 910 may be a part of operations in block 604 of Figure 6. Other operations apparent to those with ordinary skill in the art may also be performed.
  • the paths including the working path and the protection paths have been set up and the nodes of the paths are signaled, the paths are up and running and the network traffic will be carried through these paths.
  • the traffic of the failed path will be switched to another path that leads to the same destination of the failed path.
  • a new path may optionally be allocated. In one embodiment, these processes may be performed dynamically without involving a network administrator.
  • FIG 10 is a flow diagram illustrating an exemplary process for handling path failures according to one embodiment of the invention.
  • the exemplary process 1000 may be performed by a processing logic that may comprise hardware (circuitry, dedicated logic, etc.), software (such as is run on a dedicated machine), or a combination of both.
  • a notification for a path failure is received.
  • the path failure may be detected and the notification of the failure may be received in a variety of manners.
  • the failure of a path may be detected based on a loss of optical signal, such as, for example, a loss of light of a path/wavelength combination.
  • a terminating node of the corresponding optical circuit such as, for example, the source or the destination node of the optical circuit, may also be notified regarding the path failure based on a loss of the optical signal (e.g., loss of light) on a path/wavelength associated with the failed path/wavelength combination.
  • a loss of the optical signal e.g., loss of light
  • the failed path is a working path
  • it is determined what protection scheme is associated with the failed working path (e.g., 1+1, 1 :1. 1 :N, or reroutable).
  • the protection scheme of the failed working path may be determined based on the information stored in the exemplary databases shown in Figures 2B and 3. For example, based on the information stored in the exemplary database 300 of Figure 3, a protection path associated with the failed working path may be determined.
  • the protection scheme of the protection path associated with the failed working path may be determined based on the information stored in the exemplary database 250 of Figure 2B.
  • it is determined whether the protection scheme of the failed working path is a 1 :N protection scheme.
  • the protection scheme of the failed working path is a 1 :N protection scheme
  • a process for handling a failure of a working path having a 1 :N protection is performed, which will be described in details further below, such as, for example, in Figure 11 and its corresponding descriptions.
  • the protection scheme is not a 1 :N protection (e.g., 1+1, 1:1. or reroutable)
  • a process for handling a failure of a working path having a protection other than a 1:N protection is performed, which will be described in details further below, such as, for example, in Figures 13 and 14, and their corresponding descriptions.
  • the failed path is not a working path, at block 1007, it is determined whether the failed path is a protection path. If the failed path is not a protection path (e.g., an unallocated path), at block 1011, the failed path is marked broken and its status is updated from unallocated to broken.
  • a protection path e.g., an unallocated path
  • the failed path is determined to be a protection path (block 1007), at block 1008, it is determined whether the failed protection path is a 1 :N protection path. If the failed protection path is not a 1 :N protection path, at block 1010, a process for handling a failure of a protection path having a protection other than a 1 :N protection is performed. If the failed protection path is a 1 :N protection path, at block 1009, a process for handling a failure of a 1 :N protection path is performed, which will be described further in detail below. Other operations apparent to those with ordinary skill in the art may be performed.
  • FIG. 11 is a flow diagram illustrating an exemplary process for handling a failure of a working path having a 1 :N protection according to one embodiment of the invention.
  • the exemplary process 1100 may be performed by a processing logic that may comprise hardware (circuitry, dedicated logic, etc.). software (such as is run on a dedicated machine), or a combination of both.
  • the exemplary process 1 100 may be implemented as a part of operations involved in block 1006 of Figure 10.
  • the 1 :N protection path associated with the failed working path (hereinafter referred to as working path 2 or WP2) is determined and the status of the failed working path (e.g., WP2) is updated from allocated/working to broken.
  • WPl the 1:N protection path associated with WP2 is being used by another working path (hereinafter referred to as WPl). It is assumed that WPl fails before WP2 and the traffic of WPl has been switched to the 1 :N protection path shared by WPl and WP2, optionally as well as some other working paths.
  • the priorities of WPl and WP2 are compared against each other (block 1104). If the priority of WPl is lower than the priority of WP2, at block 1105, the 1 :N protection path (currently used by the traffic of WPl) is assigned to WP2 and the traffic of WP2 is switched over to the 1:N protection path.
  • a new working path is allocated for the traffic of WT 1 , which previously handled by the 1 :N protection path. In one embodiment, the working path may be allocated using the exemplary process 700 of Figure 7. The traffic of WPl is then switched over to the newly allocated working path.
  • a new 1 :N protection path may be optionally allocated for the new working path carrying the traffic of WTl.
  • the new protection path allocated for WPl may be allocated using the exemplary process 900 of Figure 9. [00130]
  • the associated databases such as those shown in Figures I, 2A-2B, and 3, are updated. For example, the status of the new WPl is updated from unallocated to allocated/working and the new protection path for the new WPl is updated dependent upon whether the new protection path for the WPl is a previously unallocated path or an existing 1 :N protection path, as described in Figure 9.
  • the protection path for the original WP 1 (now used by the traffic of WP2) no longer serves as a 1 :N protection path for WPl .
  • the priority of W 7 P 1 may be removed from the priorities of the working paths currently sharing with the 1 :N protection (e.g., field 256 of Figure 2B).
  • the original failed WPl (which may be marked as broken) is checked whether the original failed WPI has recovered. If the original failed WPl has recovered, the traffic of the current WPl may be switched back to the recovered WPl. In that case, the status of the recovered WPl may be updated from broken to allocated ; working again. Other configurations may exist.
  • the priority of WP2 is removed from the priorities of the working paths currently sharing with the 1 :N protection path (e.g., field 256 of Figure 2B), because a new path is needed for the traffic of WP2 and it is no longer under the protection of the 1 :N protection path.
  • a new working path is searched and allocated for the WP2 using, for example, the exemplary process 700 of Figure 7.
  • a new protection path is optionally searched and allocated to the new WP2 using, for example, the exemplary process 900 of Figure 9.
  • the associated databases such as, for example, those shown in Figures 1, 2A-2B, and 3. are updated.
  • the status of the new WP2 is updated from unallocated to allocated/working and the status of the new protection path may vary as described in Figure 9 and its corresponding descriptions.
  • the associated databases such as those exemplary databases shown in Figures 1 , 2A-2B, and 3, are updated.
  • FIG. 12 is a flow diagram illustrating an exemplary process for handling a failure of a 1 :N protection path according to one embodiment of the invention.
  • the exemplary process 1200 may be performed by a processing logic that may comprise hardware (circuitry, dedicated logic, etc.), software (such as is run on a dedicated machine), or a combination of both.
  • the exemplary process 1200 maybe implemented as a part of operations involved in block 1009 of Figure 10.
  • a fault notification of a 1 :N protection path is received.
  • the fault notification may be received by not receiving a light of a path/wavelength combination as an indication that the path'wavclcngth is down.
  • a new 1 :N protection path s searched and allocated, replacing the protection path at fault.
  • the new 1 ;N protection path may be searched and allocated using at least a part of the exemplary process 900 of Figure 9,
  • a working path which was using the failed protection path is determined.
  • the traffic of the failed protection path may be switched over to the new 1 :N protection path (allocated at block 1202).
  • the associated databases such as, for example, those shown in Figures 1, 2A-2B, and 3, maybe updated.
  • the status of the failed protection path may be updated from allocated/protection/ ' 1 :N/used to broken and the count of the failed protection path is reset to zero, since no working path is under the protection of the failed protection path any more.
  • the traffic of the failed protection path may be switched back to the recovered working path.
  • the associated databases such as, for example, those shown in Figures 1, 2A-2B, and 3, may be updated.
  • the status of the new protection path may be updated from unallocated to allocated/protection/ 1 :N/used.
  • the count of the failed 1 :N protection path may be copied to the new 1 :N protection path.
  • the priorities of the working path sharing the 1 :N protection path are copied to the new 1 :N protection path.
  • the status of the failed protection path may be updated from allocated/protection/ 1 :N/used to broken and its count is reset to zero. [00141) If it is determined, at block 1203, that the failed protection path is not being used, at block 1210, the associated databases, such as, for example, those shown in Figures 1, 2A-2B, and 3, may be updated. For example, the status of the new protection path may be updated from unallocated to allocated/protection- 1 :N/used. The count of the failed 1 :N protection path may be copied to the new 1 :N protection path. The priorities of the working path sharing the 1:N protection path are copied to the new 1 :N protection path.
  • any recovered path may be released back to the unallocated pool. That is, when a working path is broken, after the traffic of the broken working path has been switched over to the protection path, a new working path is searched and allocated to replace the broken working path. Subsequently, when the broken working path recovers, the recovered working path may be released back to the unallocated pool (e.g., from broken state 503 back to unallocated state 501 of Figure 5) and the status of the recovered working path is updated from broken to unallocated.
  • the unallocated pool e.g., from broken state 503 back to unallocated state 501 of Figure 5
  • the traffic of the protection path may be switched over to the new working path and the associated databases may be updated accordingly.
  • the traffic of the protection path may be switched over to the new working path immediately and the protection path becomes available (e.g., the status of the protection path is updated from allocated/protection/ 1 :N/used to allocated/protection/ 1 :N).
  • Other configurations apparent to those with ordinary skill in the art may exist.
  • Figure 13 is a flow diagram of an exemplary process for handling a path failure having a 1+1 or 1:1 protection scheme according to one embodiment of the invention.
  • the exemplary process 1300 may be performed by a processing logic that may comprise hardware (circuitry, dedicated logic, etc.), software (such as is run on a dedicated machine), or a combination of both, hi one embodiment, the exemplary process 1300 may be implemented as a part of operations involved in block 1010 of Figure 10.
  • a fault notification of a path having a 1+1 or 1:1 protection scheme is received.
  • the failed path maybe a working path or a protection path of a 1-M or 1:1 protection scheme.
  • the associated databases such as, for example, those shown in Figures 1, 2A-2B, and 3, are updated.
  • the status of the failed working path is updated from allocated/working to broken.
  • the status of the protection path is updated from allocated/protection/l:l to allocated ''protection/ 1 : 1 /used,
  • the processes for handling a recovery of a path may be performed using the exemplary process 1500 of Figure 15, which will be described in details further below.
  • the associated databases such as, for example, those shown in Figures 1, 2A-2B, and 3, maybe updated.
  • the status of the failed protection path is updated from allocated/protection' 1+1 or 1 : 1 to broken and the status of the original working path is updated to allocated/working.
  • a new protection path may be allocated for the recovered working path, using, for example, the exemplary process 800 of Figure 8.
  • the traffic of the failed protection path is switched to the new working path.
  • the associated databases is updated. For example, the status of the failed protection path is updated from allocated/protection'1+1 or 1 :1 to broken.
  • the status of the new working path is updated from unallocated to allocated/working and the status of the new protection path is updated from unallocated to allocated/protection/1+1 or 1 :1.
  • Other operations apparent to those with ordinary skill in the art may be performed.
  • the recovered working path may be released back to the unallocated pool (e.g., from broken state to unallocated state as shown in Figure 5).
  • the operations of blocks 1305-1308 may be skipped and a new working path is always searched and allocated as performed in blocks 1309-131 1.
  • the traffic of a protection path carrying for the then failed working path and now recovered working path may be switched back to the recovered working path without waiting for the failure of the protection path.
  • the protection path is then released (e.g.. not being used).
  • the status of the recovered working path may be updated from broken to allocated/ working and the status of the protection path may be updated from allocated/protection/1+1 or 1: I/used to allocated/protection/ 1+1 or 1 :1.
  • [0015GJ Figure 14 is a flow diagram illustrating an exemplary process for handling a failure of a reroutable path according to one embodiment of the invention.
  • the exemplary process 1400 may be performed by a processing logic that may comprise hardware (circuitry, dedicated logic, etc.), software (such as is run on a dedicated machine), or a combination of both. In one embodiment, the exemplary process 1400 may be implemented as a part of operations involved in block 1010 of Figure 10.
  • a fault notification of a reroutable path is received.
  • a new reroutable path is searched and allocated from a set of available paths that lead to the destination of the failed reroutable path and have one or more unallocated channels (e.g., path/ wavelength combination).
  • the search may be conducted using the exemplary database organization shown in Figures 2A and 2B. If a new reroutable path cannot be located, the demand is dropped.
  • the traffic of the failed path is switched over to the new reroutable path.
  • the associated databases such as, for example, those shown in Figures 1, 2A-2B, and 3, are updated.
  • the status of the failed reroutable path is updated from allocated/working to broken and the status of the new reroutable path may be updated from unallocated to allocated/working.
  • Other operations apparent to those with ordinary skill in the art may also be performed.
  • Figure 15 is a flow diagram illustrating an exemplary process for handling a recovery of a working path according to one embodiment of the invention.
  • the exemplary process 1500 may be performed by a processing logic that may comprise hardware (circuitry, dedicated logic, etc.), software (such as is run on a dedicated machine), or a combination of both.
  • a notification of a working path recovery is received.
  • a protection path currently carrying the traffic of the previously failed, now recovered working path is determined. In one embodiment, the determination is performed based on the information stored in the exemplary databases shown in Figures 2A-2B and 3.
  • the traffic of the protection path currently may be switched back to the recovered working path.
  • the associated databases such as, for example, those shown in Figures 1 , 2A-2B, and 3, may be updated. For example, the status of the recovered working path may be updated from broken to allocated/working and the status of the protection path may be updated from allocated/protection/ 1+1, 1:1.
  • the traffic would not be switched from the protection path back to the recovered working path until the protection path fails.
  • the working path may be released back to the unallocated pool (e.g., the status or state transitions from broken to unallocated).
  • protection path When protection path is searched, typically, according to one embodiment, a fully node disjoint path with respect to a working path is searched and allocated. However, there are some cases that a protection path that satisfies the disjointness constraints with respect to a working path cannot be found. In this case, an optional contention resolution may be performed. During a contention resolution, another protection path may be preempted or dumped, if the protection scheme of the instance search has a higher priority than an existing protection path. In one embodiment, the priority order of the protection scheme from high to low is 1+1, 1 :1, 1 :N. and reroutable.
  • a protection path may be searched or allocated based on a disjointness preference order specified by a network owner or a service provider.
  • a default disjointness preference order from high to low is fully node disjointness, fully edge/link disjointness. maximally node disjointness, and maximally edge/link disjointness.
  • the disjointness preference order and/or the protection scheme priority may be specified by a network owner or service provider, which may be stored in a preference database of the network owner or service provider, such as, for example, exemplary database 104 of Figure 1.
  • Figure 16 is a block diagram illustrating an exemplary disjointness preference order and an exemplary protection scheme priority order, according to one embodiment of the invention.
  • exemplary embodiment 1600 includes, but not limited to, exemplary disjointness preference order 1601 and exemplary protection scheme priority order 1602.
  • the exemplary disjointness preference order 1601 and exemplary protection scheme priority order 1602 maybe specified by the network owner or sendee pro ⁇ ider in a preference database, such as, for example, exemplary preference database 104 of Figure 1.
  • exemplary disjointness preference order 1601 includes, from high to low order, fully node disjointness 1603, fully edge/link disjointness 1604, maximally node disjointness 1605, and maximally edge/link disjointness 1606.
  • exemplary protection scheme priority order 1602 includes, from high to low priority, 1+1 protection 1607, 1 : 1 protection 1608. 1:N protection 1609, and reroutable 1610.
  • the protection path when a protection path is searched but cannot be found, the protection path is searched based on the exemplary disjointness preference order and for each disjointness preference the search is conducted against other existing protection paths having lower protection scheme priority based on the exemplary protection scheme priority order 1602. If a protection path having lower protection scheme priority is found, the protection path found may be preempted or bumped. As a result, the preempted protection path may be allocated to the instant demand and a new path may be searched and allocated for the preempted path. [00162] For example, referring to Figure 16, when a protection path in demand for a specific protection path cannot be found, typically for a fully node disjoint protection path with respect to a working path.
  • a search is conducted to locate other fully node disjoint protection paths having a lower protection scheme priority.
  • the search is performed from a low to high priority of the priority of the protection scheme (e.g.. protection scheme priority order 1602).
  • a search is performed to locate a reroutable path having priority 1610. If the search is successful, the located path is preempted (e.g., bumped) and assigned to the demand. Another path may be allocated for the preempted path. If the search is unsuccessful, a path having a next higher priority (e.g. fully node disjoint protection path having 1 :N protection scheme) is searched, and so on.
  • disjoint preference order 1601 and the protection scheme priority order 1602 are shown for illustrative purposes only.
  • the orders of the disjoint preference order 1601 and the protection scheme priority order 1602 may vary. In one embodiment, they may be determined based on the information stored in a preference database specified by a network owner or service provider (e.g., database 104 of Figure 1).
  • the exemplary contention resolution is not limited to optical networks. It will be appreciated that the exemplary contention resolution described herein may be applied to other types of networks.
  • FIG 17 is a flow diagram illustrating an exemplary process for handling a contention resolution according to one embodiment of the invention.
  • the exemplary process 1700 may be performed by a processing logic that may comprise hardware (circuitry, dedicated logic, etc.), software (such as is run on a dedicated machine), or a combination of both.
  • a demand for a contention resolution of a protection path is received and the demand includes the protection scheme type.
  • a disjointness type from a disjoint preference order e.g., disjoint preference order 1601
  • a protection scheme type is selected from the protection scheme priority order (e.g., protection scheme priority order 1602) using a bottom-up approach (e.g., from low priority 1610 to high priority 1607).
  • the selected protection scheme priority is lower than the one in demand.
  • a path is selected that satisfies the selected disjoint preference and the selected protection scheme priority. If, at block 1706, that such a path is found, at block 1707. the path found is preempted or bumped and assigned or allocated to the demand.
  • the associated databases such as, for example, those shown in Figures 1 , 2A-2B, and 3, are updated as described above. Thereafter, at block 1708, the traffic of the preempted or bumped path may be rerouted and the associated databases are updated, which will be described in details farther below.
  • the selected protection scheme priority is higher than or equal to the priority in demand (e.g., all protection scheme priorities of the priority order 1602 have been searched for a given disjoint preference selected from the disjoint preference order 1601)
  • it is determined whether there are more disjoint preferences that have not been processed from the disjoint preference order e.g., disjoint preference order 1601. If so. a next disjoint preference in the order from the disjoint preference order (e.g., disjoint preference order 1601) is selected and the processes repeat from block 1702, until no more disjoint preference is left, in which case, at block 1710, the demand is dropped.
  • Figure 18 is a block diagram illustrating an exemplary process for rerouting a path that has been preempted by a contention resolution, according to one embodiment of the invention.
  • the exemplary process 1800 may be performed by a processing logic that may comprise hardware (circuitry, dedicated logic, etc.), software (such as is run on a dedicated machine), or a combination of both.
  • the exemplary process 1800 may be a part of operations involved in block 1708 of Figure 17.
  • a demand for rerouting a preempted path is received.
  • a disjoint preference is selected according to a disjoint preference order, such as, for example, disjoint preference order 1601 of Figure 16.
  • the preference order may be set up and stored by a network owner or service provider in a preference database, such as, for example, preference order 104 of Figure 1.
  • a reroutable path for a given disjoint preference is searched, based on, for example, the exemplary database organizations shown in Figures 2 A-2B and 3.

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  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
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  • Optical Communication System (AREA)

Abstract

Cette invention se rapporte à des procédés et à des appareils destinés à des systèmes à redondances multiples dans un réseau optique. Dans un mode de réalisation, un procédé donné à titre d'exemple comprend les étapes consistant à recevoir une demande d’attribution d’un premier chemin de protection qui répond à un premier ensemble de contraintes de disjonction en ce qui concerne un premier chemin qui fonctionne selon un premier système de protection qui présente une première priorité, en réponse à la demande, à localiser un deuxième chemin de protection qui répond à un deuxième ensemble de contraintes de disjonction en ce qui concerne un deuxième chemin qui fonctionne selon un deuxième système de protection qui présente une deuxième priorité et attribuer le deuxième chemin de protection comme chemin de protection au premier chemin qui fonctionne si la première priorité du premier système de protection est plus élevée que la deuxième priorité du deuxième système de protection. D'autres procédés et appareils sont également décrits.
PCT/US2008/078029 2008-09-26 2008-09-26 Systèmes à redondances multiples dans un réseau optique WO2010036267A1 (fr)

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WO2014094314A1 (fr) * 2012-12-22 2014-06-26 华为技术有限公司 Procédé de sélection de meilleur chemin, dispositif associé et système de communication
CN113810793A (zh) * 2020-06-12 2021-12-17 中兴通讯股份有限公司 资源部署方法、设备、管控系统及计算机存储介质

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