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Berkeley COMPSCI 294 - IP over WDM network

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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 PresentationOutlineHistory of WDM networksCurrent Internet: Multi-layer protocol stack between IP and WDM layersFuture: IP directly over WDMChallengeVirtual Topology ReconfigurationMulti-layer routingOne proposal: Optical Burst Switching technologiesHistoryIn the late 70sFirst fiber based optical transmission systemBefore 1995Mostly a single high-speed optical channel All multiplexing done in electrical domain(TDM)50Mb/s to 10Gb/s data servicesAfter 1995WDM 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 StackInefficientIn IP over ATM over SONET over WDM network, 22% bandwidth used for protocol overheadLayers 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 protectionOptical 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 thingRoutingProtectionsSlow speedElectronic devices can not catch the transmission speed available at optical layerLatencies of connectionHistorical Reason for Multi-layerSONET over WDMConventional WDM deployment is using SONET as standard interface to higher layersIP over ATMIP packets need to be mapped into ATM cells before transporting over WDM using SONET frameOEO 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 networkWDM-aware Electronic layerReconfiguration and load balancingProtection and restorationOptical flow switchingNetwork management/controlCross-layer optimizationReconfigurable (within milli-seconds) OXCWavelength ConvertersNo  converters123New request 1 3123New request 1 3With  convertersWCVirtual Topology ReconfigurationPhysical topologySeen 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 byChanging the light path connectivity between electronic switchesTuning 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 patternLoad balancingEfficiencyIssues:Time scale of changesTriggered by what mechanismsIP 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 RoutingIP layer routing is the bottleneck of present InternetSolution: 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 processingOptical 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 SwitchingRetrospect the goal of IP over WDM: Avoid electronic bottlenecks Decrease the cost by simplifying the multiple layer architectureOBS is one proposal of how to realize such a networkOptical Burst SwitchingResources are allocated using one way reservationSender sends a requestSender sends burst without waiting for an acknowledgement of its reservation requestSwitch does preparation for the burst when getting the requestBursts can have variable lengthsBurst switching does not necessarily require bufferingVarious OBSsThe 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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Berkeley COMPSCI 294 - IP over WDM network

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