Presentation on theme: "Protection and Restoration in Optical Network"— Presentation transcript:
1Protection and Restoration in Optical Network Ling Huang
2Introduction to Network Survivability Optics in Internet OutlineIntroduction to Network SurvivabilityOptics in InternetProtection and Restoration in InternetOptical Layer SurvivabilityProtection in Ring NetworkProtection in Mesh NetworkMulti-Layer ResilienceConclusion.
3Network Survivability A 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.
4Optics in the Internet Access Long Haul Metro SONETDataCenterDWDMAccessLong HaulMetroBPS2000, Baystack 450 & Passport 8600 (edge ethernet distribution & aggregation)OPTera Packet Edge on OPTera Metro 3000 series & OPTera OC-48 (ethernet over metro optical/Sonet)OPTera Metro 5000 series (ethernet over DWDM)Preside (provisioning & management software)Juniper & Shasta (collateral IP services & routing platforms)Contivity (VPN/secure, encrypted tunnel services)
5Optical Network: a Layered vision Multi-physical layersmulti & legacy servicesrobustness, QOSThin SONETIPOpticsMPLSFewer physical layersIP service dominancelower costSONETATMLayer321PacketOpticalInter-workingSmart OpticalIP/MPLS2/30/1Migration to IP on Opticssimpler, lower cost networkrobustness & QOS needed for some services200119992002
6Protection and Restoration in Internet A 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 minutes
7Why Optical Layer Protection Restoration 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.
8Why 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.
9Protection Technique Classification Restoration 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 networks
10Protection in Ring Network 1+1 Path ProtectionUsed in access rings for traffic aggregation into central office1:1 Span and Line ProtectionUsed in metropolitan or long- haul rings1:1 Line ProtectionUsed for interoffice rings
11Protection in Mesh Networks Network planning and survivability designDisjoint path idea: service working route and its backup route are topologically diverse.Lightpaths of a logical topology can withstand physical link failures.Working PathBackup Path
12Reactive / Proactive Reactive Proactive A 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 recoveryTaxonomy
13Path Protection / Line Protection Path Switching: restoration is handled by the source and the destination.Line Switching: restoration is handled by the nodes adjacent to the failure.Line Protection.Normal OperationLine Switching: restoration is handled by the nodes adjacent to the failure Span Protection: if additional fiber is available.
141+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 bandwidth
151:1 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.
16Shared ProtectionNormal Operation1:N ProtectionIn Case of FailureBackup fibers are used for protection of multiple linksAssume independent failure and handle single failure.The capacity reserved for protection is greatly reduced.
17Multiplexing Techniques Primary Backup MultiplexingUsed 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.
18Survivability Design: Joint Optimization Problem Problem 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 set of links;D: the set of demandsCij: the capacity weight for link (ij)Wij: the capacity requirement on link (ij) in terms of # of wavelengthObjectiveMinimize
19Integer Programming Formulation 1) Objective function2) and 3) the flow conservation constraints for demand d’s primary path and backup path, respectively.4) Logical relationship: the backup path consumes link capacity iff the primary path is affected by the fault.5): Restoration route independent of the failure.6): Link capacity requirement
25ConclusionDifferent resilience schemes applicable in optical network have been discussed.Network planning and topology design for survivability is computationally intractable and faster heuristic solutions are needed.Multi-layer restoration is a hot point in current optical survivability research.Joint IP/optical restoration mechanism is the trend in next generation optical network.
26Unidirectional Path Switched Ring (UPSR) Signal sent on both working and protected pathBest quality signal selectedReceiving TrafficSending TrafficN2N1Outside Ring = WorkingInside Ring = ProtectionN3N4N1 send data to N2
27Unidirectional Path Switched Ring (UPSR) Signal sent on both working and protected pathBest quality signal selectedReply TrafficReceiving TrafficN2N1Outside Ring = WorkingInside Ring = ProtectionN3N4N2 replies back to N1
28Bidirectional Line Switched Ring (2-Fiber BLSRs) Sending/ReceivingTrafficSending/ReceivingTrafficN2N1Both Rings = Working & ProtectionN3N4N1 send data to N2 & N2 replies to N1
29Bidirectional Line Switched Ring (4-Fiber BLSRs) Sending/ReceivingTrafficSending/ReceivingTrafficN2N1OC-482 Outside Rings = Working2 Inside Rings = ProtectionN3N4N1 send data to N2 & N2 replies to N1