IP over WDM networkOutlineHistoryCurrent Typical Protocol StacksTransport Layer ModelDisadvantage of Current Multi-layer Protocol StackDisadvantage of Current Multi-layer Protocol Stack (Cont)Historical Reason for Multi-layerSimplified Protocol Stacks?IP Directly Over WDM?Challenge for IP over WDM networkVirtual Topology ReconfigurationVirtual Topology Reconfiguration(Cont.)Multi-layer RoutingSwitching all the packets in optical layer?Various Optical Switching TechnologiesOptical Burst Packet SwitchingOptical Burst SwitchingVarious OBSsMain Characteristics of Optical Burst SwitchingConclusionReferenceIP over WDM networkFang Yu294 Class PresentationOutlineHistory of WDM networksCurrent Internet: Multi-layer protocol stack between IP and WDM layersFuture: IP directly over WDMChallengeVirtual Topology ReconfigurationMulti-layer routingOne proposal: Optical Burst Switching technologiesHistoryIn the late 70sFirst fiber based optical transmission systemBefore 1995Mostly a single high-speed optical channel All multiplexing done in electrical domain(TDM)50Mb/s to 10Gb/s data servicesAfter 1995WDM allows simultaneously transmitting multiple high-speed channels on different frequencies (Up to 160 wavelengths today)40G per (OC768)Total link capacity = 160 *40G =6.4 TbpsCurrent Typical Protocol StacksIPATMSONETWDMN e t w o r kP h y s i c a lD a t a l i n kN e t w o r kSONETATMIPD a t a l i n kD a t a l i n kN e t w o r kWDMProprietary(20-400 Gb/s)OTS OTS OTS OTS OTS OTS(OTS: Optical Transport System)Transport Layer Model“Packet”“Packet”“Packet”“Packet”1/0 DCS1/0 DCS1/0 DCS1/0 DCS4E4E4E4E3/1 DCS3/1 DCS3/1 DCS3/1 DCS3/3 DCSLayer (DACS III)DACS III DACS IIIDACS IIIDACS IIIATM/IPATM/IPATM/IPATM/IPDS1(1.5 Mb/s)DS3(45 Mb/s)DS3(45 Mb/s)OC48+(2.5+ Gb/s)ADMADMADMADMADMADMADMFiber Conduit/Sheath3/1 DCSLayerSONET ADMLayerCore ATM/IPLayersServiceLayersMediaLayerLACHCGLALALALALALAPHNXPHNXPHNXCHCGCHCGCHCGCHCGCHCGWavelength Path CrossconnectWavelength Mux Section CrossconnectHard-WiredDisadvantage of Current Multi-layer Protocol StackInefficientIn IP over ATM over SONET over WDM network, 22% bandwidth used for protocol overheadLayers often do not work in concert Every layer now runs at its own speed. So, low speed devices cannot fill the wavelength bandwidth. When detecting of failure, different layers compete for protectionOptical layer detects failure almost immediately, restores error in 2us to 60ms SONET layer detects failure in 2.3–100 us, restores error in 60 msDisadvantage of Current Multi-layer Protocol Stack (Cont)Functional overlap: So many layers are doing the same thingRoutingProtectionsSlow speedElectronic devices can not catch the transmission speed available at optical layerLatencies of connectionHistorical Reason for Multi-layerSONET over WDMConventional WDM deployment is using SONET as standard interface to higher layersIP over ATMIP packets need to be mapped into ATM cells before transporting over WDM using SONET frameOEO conversions at every node is easier to build than all optical switchElectronic NetworkElectronic NetworkElectronic NetworkElectronic NetworkO/E/OO/E/OO/E/OO/E/OO/E/OO/E/OOptical CoreE/OE/O E/OE/OSimplified Protocol Stacks?IPFrame RelayATMSONETWDMIPWDMWDM-awareElectronic layerCurrent Typical Protocol Stack Simplified Protocol StackIP Directly Over WDM? Establish high-speed optical layer connections (lightpaths)IP routers connected through lightpaths rather than fiberAB CDE W a v e l e n g t hc r o s s c o n n e c tL i g h t p a t h sI P r o u t e rChallenge for IP over WDM networkWDM-aware Electronic layerReconfiguration and load balancingProtection and restorationOptical flow switchingNetwork management/controlCross-layer optimizationReconfigurable (within milli-seconds) OXCWavelength ConvertersNo converters123New request 1 3123New request 1 3With convertersWCVirtual Topology ReconfigurationPhysical topologySeen by optical layer Virtual topology: a set of nodes interconnected by light-paths (wavelength)Seen by electronic layer Reconfigure of light-paths in WDM network byChanging the light path connectivity between electronic switchesTuning of the transmitter wavelength and the frequency-selective-switchesA AB BC D C DVirtual Topology Reconfiguration(Cont.)Enable network to dynamically response to changing of traffic patternLoad balancingEfficiencyIssues:Time scale of changesTriggered by what mechanismsIP routing properties (e. g. stability)0.10.010.0010.01 0.02 0.03Blocking Probability0.04FixedRoutingReconfigurableRouting0.05X6Call arrival rateWDM ring, 20 nodesone transceiver/nodecall BW = 1 wavelengthMulti-layer RoutingIP layer routing is the bottleneck of present InternetSolution: Routing long duration flows at lower layers•Conventional packet routing•Optical bypass of intermediate routers for high volume traffic•End-to end (user-to-user) flow of entire file bypassing routersUser 1 User 2Router 1Router 2Router 3WDM layer. . .. . .Network control LIDSSwitching all the packets in optical layer?Requires intelligence in the optical layer Need to store packet during header processingOptical buffers are extremely hard to implement 1 pkt = 12 kbits @ 10 Gbps requires 1.2 s of delay => 360 m of fiber)Optical Packet Switch still has a long way to go………………………Various Optical Switching TechnologiesOptical Burst Packet SwitchingRetrospect the goal of IP over WDM: Avoid electronic bottlenecks Decrease the cost by simplifying the multiple layer architectureOBS is one proposal of how to realize such a networkOptical Burst SwitchingResources are allocated using one way reservationSender sends a requestSender sends burst without waiting for an acknowledgement of its reservation requestSwitch does preparation for the burst when getting the requestBursts can have variable lengthsBurst switching does not necessarily require bufferingVarious OBSsThe schemes differ in the way bandwidth release is triggered.In-band-terminator (IBT) – header carries the routing information, then the payload followed by silence (needs to be done optically).Tell-and-go (TAG) – a control packet is sent out to reserve resources and then the burst is sent without waiting for
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