Protection and Restoration in Optical NetworkOutlineNetwork SurvivabilityOptics in the InternetOptical Network: a Layered visionProtection and Restoration in InternetWhy Optical Layer ProtectionWhy Optical Layer Protection?Protection Technique ClassificationProtection in Ring NetworkProtection in Mesh NetworksReactive / ProactivePath Protection / Line Protection1+1 Protection1:1 ProtectionShared ProtectionMultiplexing TechniquesSurvivability Design: Joint Optimization ProblemPowerPoint PresentationMulti-Layer ResilienceSlide 21Multi-Layer Counter-Productive BehaviorMulti-Layer InteractionSlide 24ConclusionUnidirectional Path Switched Ring (UPSR)Slide 27Bidirectional Line Switched Ring (2-Fiber BLSRs)Bidirectional Line Switched Ring (4-Fiber BLSRs)UCBProtection and Restoration in Optical NetworkLing [email protected]Introduction to Network SurvivabilityOptics in InternetProtection and Restoration in InternetOptical Layer SurvivabilityProtection in Ring NetworkProtection in Mesh NetworkMulti-Layer ResilienceConclusion.UCBNetwork SurvivabilityA very important aspect of modern networksThe ever-increasing bit rate makes an unrecovered failure a significant loss for network operators.Cable cuts (especially terrestrial) are very frequent.No network-operator is willing to accept unprotected networks anymore.Restoration = function of rerouting failed connectionsSurvivability = property of a network to be resilient to failureRequires physical redundancy and restoration protocols.UCBOptics in the InternetSONETDataCenterSONETSONETSONETDWDMDWDMAccessLong HaulAccessMetroMetroUCBOptical Network: a Layered visionMulti-physical layers• multi & legacy services• robustness, QOSThin SONETIPOpticsMPLSFewer physical layers• IP service dominance• lower costSONETIPOpticsATMLayeLayerr33221100PacketOpticalInter-workingSmart Optical Smart Optical PacketIP/MPLSPacketIP/MPLSLayeLayerr 2/32/30/10/11999 20022001UCBProtection and Restoration in InternetA well defined set of restoration techniques already exists in the upper electronic layers:ATM/MPLSIPTCPRestoration speeds in different layers:BGP-4: 15 – 30 minutesOSPF: 10 seconds to minutesSONET: 50 millisecondsOptical Mesh: currently hundred milliseconds to minutesUCBWhy Optical Layer ProtectionRestoration in the upper layers is slow and require intensive signalingOn contrary 50-ms range when automatic protection schemes are implement in the optical transport layer.Purpose of performing restoration in the optical layer:To decrease the outage time by exploiting fast rerouting of the failed connection.Main problem in adding protection function in a new layer:Instability due to duplication of functions.Need the merging of DWDM and electronic transport layer control and management.UCBWhy Optical Layer Protection?Advantages.Speed.Efficiency.LimitationDetection of all faults not possible.(3R).Protects traffic in units of light paths.Race conditions when optical and client layer both try to protect against same failure.UCBProtection Technique ClassificationRestoration techniques can protect the network against:Link failuresFiber-cables cuts and line devices failures (amplifers)Equipment failuresOXCs, OADMs, eclectro-optical interface.Protection can be implementedIn the optical channel sublayer (path protection)In the optical multiplex sublayer (line protection)Different protection techniques are used forRing networksMesh networksUCBProtection in Ring Network1+1 Path ProtectionUsed in access rings for traffic aggregation into central office 1:1 Line ProtectionUsed for interoffice rings1:1 Span and Line ProtectionUsed in metropolitan or long- haul ringsUCBProtection in Mesh NetworksWorking PathBackup PathNetwork planning and survivability design Disjoint path idea: service working route and its backup route are topologically diverse.Lightpaths of a logical topology can withstand physical link failures.UCBReactiveA search is initiated to find a new lightpath which does not use the failed components after the failure happens.It can not guarantee successful recovery,Longer restoration timeProactiveBackup lightpaths are identified and resources are reserved at the time of establishing the primary lightpath itself.100 percent restorationFaster recoveryReactive / ProactiveTaxonomyUCBPath Switching: restoration is handled by the source and the destination.Normal OperationLine Switching: restoration is handled by the nodes adjacent to the failure. Span Protection: if additional fiber is available.Line Switching: restoration is handled by the nodes adjacent to the failure. Line Protection.Path Protection / Line ProtectionUCB1+1 ProtectionTraffic is sent over two parallel paths, and the destination selects a better one.In case of failure, the destination switch onto the other path.Pros: simple for implementation and fast restorationCons: waste of bandwidthUCB1:1 ProtectionDuring normal operation, no traffic or low priority traffic is sent across the backup path.In case failure both the source and destination switch onto the protection path.Pros: better network utilization.Cons: required signaling overhead, slower restoration.UCBShared Protection1:N ProtectionBackup fibers are used for protection of multiple linksAssume independent failure and handle single failure.The capacity reserved for protection is greatly reduced.Normal OperationIn Case of FailureUCBPrimary Backup Multiplexing Used in a dynamic traffic scenario, to further improve resource utilization.Allows a wavelength channel to be shared by a primary and one or more backup paths. By doing so, the blocking probability of demands decreases at the expense of reduced restoration guarantee. (An increased number of lightpaths can be established)•A lightpath loses its recoverability when a channel on its backup lightpath is used by some other primary lightpath.•It regains its recoverability when the other primary lightpath terminates.Multiplexing TechniquesUCBProblem DescriptionGiven a network in terms of nodes (WXCs) and links, and a set of point-to-point demands, find both the primary lightpath and the backup lightpath for each demand so that the total required network capacity is minimized.NotationN: the set of nodes; L: the
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