ATM Networks: An OverviewOverviewATMATM vs Phone NetworksATM vs Data NetworksOld House vs New HouseATM InterfacesSlide 8Protocol LayersSlide 10Virtual Circuit SwitchingCell Header FormatHeader Error Check (HEC)Payload Type Field CodingPath vs ChannelsVP/VC Assignment/UseOriginal Classes of TrafficAAL 5AAL2Cell-Stream PhySONETSignal HierarchySTS-3c Frame FormatSONET/SDH PhySONET STS-3cPhysical MediaSummaryHomeworkRaj JainThe Ohio State University1ATM Networks:ATM Networks:An OverviewAn OverviewRaj Jain Professor of Computer and Information SciencesThe Ohio State UniversityColumbus, OH 43210-1277http://www.cse.ohio-state.edu/~jain/CIS677-98/Raj JainThe Ohio State University2ATM vs Phone Networks and Data NetworksATM Protocol LayersCell Header Format, AALs Physical Media OverviewOverviewRaj JainThe Ohio State University3ATMATMAsynchronous Transfer ModeATM Net = Data Net + Phone NetCombination of Internet method of communication (packet switching) and phone companies’ method (circuit switching)ATMRaj JainThe Ohio State University4ATM vs Phone NetworksATM vs Phone NetworksCurrent phone networks are synchronous (periodic). ATM = Asynchronous Transfer ModePhone networks use circuit switching. ATM networks use “Packet” SwitchingIn phone networks, all rates are multiple of 8 kbps.With ATM service, you can get any rate.You can vary your rate with time.With current phone networks, all high speed circuits are manually setup. ATM allows dialing any speed.125 sRaj JainThe Ohio State University5ATM vs Data NetworksATM vs Data NetworksSignaling: Internet Protocol (IP) is connectionless.You cannot reserve bandwidth in advance.ATM is connection-oriented. You declare your needs before using the network.PNNI: Path based on quality of service (QoS)Switching: In IP, each packet is addressed and processed individually. Traffic Management: Loss based in IP.ATM has 1996 traffic management technology.Required for high-speed and variable demands.Cells: Fixed size or small size is not importantRaj JainThe Ohio State University6Old House vs New HouseOld House vs New HouseNew needs:Solution 1: Fix the old house (cheaper initially)Solution 2: Buy a new house (pays off over a long run)Raj JainThe Ohio State University7PrivateNNIPrivateUNIATM InterfacesATM InterfacesComputerPrivateSwitchPublicSwitchRouterDigitalServiceUnitDXIB-ICIPublicUNIPublicNNIPrivateUNIPrivateSwitchPublicSwitchCarriersPublicSwitchCarrierComputerRaj JainThe Ohio State University8ATM InterfacesATM InterfacesUser to Network Interface (UNI): Public UNI, Private UNINetwork to Node Interface (NNI): Private NNI (P-NNI)Public NNI =Inter-Switching System Interface (ISSI)Intra-LATA ISSI (Regional Bell Operating Co)Inter-LATA ISSI (Inter-exchange Carriers) Broadband Inter-Carrier Interface (B-ICI)Data Exchange Interface (DXI)Between routers and ATM Digital Service Units (DSU)Raj JainThe Ohio State University9ATM LayerATM Adaptation LayerPhysicalLayerATM LayerPhysicalLayerATM LayerATM Adaptation LayerPhysicalLayerEnd System End SystemSwitchProtocol LayersProtocol LayersRaj JainThe Ohio State University10Protocol LayersProtocol LayersThe ATM Adaptation LayerHow to break messages to cellsThe ATM LayerTransmission/Switching/ReceptionCongestion Control/Buffer managementCell header generation/removal at source/destinationCell address translationSequential deliveryRaj JainThe Ohio State University117492Virtual Circuit SwitchingVirtual Circuit SwitchingCircuit Switching: bits coming on wire 4 go on wire 2Virtual Circuit Switching: Cells coming on VCI=4 go on VCI=2Raj JainThe Ohio State University12Cell Header FormatCell Header FormatGFC = Generic Flow Control(Was used in UNI but not in NNI)VPI/VCI = 0/0  Idle cell; 0/n  SignalingVCI PTIHeader Error Check (HEC)VCIVPI VCIGFC/VPI VPICLPPayloadRaj JainThe Ohio State University13Header Error Check (HEC)Header Error Check (HEC)1 + x + x2 + x8Protects header onlyOptional Correction mode: Correct one bit errors if no earlier errorsDiscard cells with bad HECRecalculated on each hopCorrectionModeDetectionModeErrorCorrect if possibleNo ErrorErrorNo ErrorRaj JainThe Ohio State University14Payload Type Field CodingPayload Type Field Coding000User data cell, no congestion, AAU = 0001User data cell, no congestion, AAU = 1010User data cell, congestion, AAU = 0011 User data cell, congestion, AAU = 1100Segment Operation and management (OAM) cell101End-to-end OAM cell110 Resource management cell111 ReservedATM-user-to-ATM-user (AAU) bit available for user-to-user indicationRaj JainThe Ohio State University15Path vs ChannelsPath vs Channels24/28-bit connection identifierFirst 8/12 bits: Virtual Path, Last 16 bits: Virtual CircuitVP service allows new VC's w/o orders to carriersVC1VC2VC3VC1VC2VC3VC1VC2VC3VP1VP2VP3LinkRaj JainThe Ohio State University16VP/VC Assignment/UseVP/VC Assignment/UseSwitch33 56Video Data37 34VoiceData213453556657661122Port0/370/340/330/56VPI/VCIIn1/350/560/654/76VPI/VCI3456PortOutRaj JainThe Ohio State University17Original Classes of Original Classes of TrafficTrafficClass A Class B Class C Class DTime Sync Yes Yes No NoBit Rate Constant Variable Variable VariableConnection-OrientedYes Yes Yes NoExamples CircuitEmulationComp.VideoFrameRelaySMDSAAL AAL1 AAL2 AAL3 AAL4Raj JainThe Ohio State University18AAL 5AAL 5Designed for data trafficLess overhead bits than AAL 3/4  Simple and Efficient AAL (SEAL)No per cell length field, No per cell CRCPADUserPayloadLength CRC-32Control4220-64kB10PTI bit indicates last cell0-47Raj JainThe Ohio State University19AAL2AAL2Ideal for low bit rate voiceVariable/constant rate voiceMultiple users per VCCompression and Silence suppressionIdle channel suppressionCellHeaderCellHeaderPayload 1PktHdrPayload 2 Payload 3PktHdrPktHdrPayload 1PktHdrPayload 2 Payload 3PktHdrPktHdrPayload 1 Payload 2 Payload 3Raj JainThe Ohio State University20Cell-Stream PhyCell-Stream PhyContinuous stream of cells. No framing.Hunt bit-by-bit for correct header.Look for  correct headers before entering synch state incorrect headers  resynchronize and  are parameters.CellHuntPresync SyncCorrect HEC Incorrect HEC Correct HECsIncorrect HECRaj JainThe Ohio State University21SONETSONETSynchronous optical networkStandard for digital optical transmission (bit