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Raj JainThe Ohio State University1ATM Networks:ATM Networks:An OverviewAn OverviewRaj JainProfessor of Computer and Information SciencesThe Ohio State UniversityColumbus, OH 43210-1277http://www.cis.ohio-state.edu/~jain/CIS677-98/Raj JainThe Ohio State University2q ATM vs Phone Networks and Data Networksq ATM Protocol Layersq Cell Header Format, AALsq Physical MediaOverviewOverviewRaj JainThe Ohio State University3ATMATMq Asynchronous Transfer Modeq ATM Net = Data Net + Phone Netq Combination of Internet method ofcommunication (packet switching) and phonecompanies’ method (circuit switching)ATMRaj JainThe Ohio State University4ATM vs Phone NetworksATM vs Phone Networksq Current phone networks are synchronous (periodic).ATM = Asynchronous Transfer Modeq Phone networks use circuit switching.ATM networks use “Packet” Switchingq 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.q With current phone networks, all high speed circuitsare manually setup. ATM allows dialing any speed.125 µsRaj JainThe Ohio State University5ATM vs Data NetworksATM vs Data Networksq Signaling: Internet Protocol (IP) is connectionless.You cannot reserve bandwidth in advance.ATM is connection-oriented.You declare your needs before using the network.q PNNI: Path based on quality of service (QoS)q Switching: In IP, each packet is addressed andprocessed individually.q Traffic Management: Loss based in IP.ATM has 1996 traffic management technology.Required for high-speed and variable demands.q Cells: Fixed size or small size is not importantRaj JainThe Ohio State University6Old House vs New HouseOld House vs New Houseq 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 Interfacesq User to Network Interface (UNI):Public UNI, Private UNIq Network to Node Interface (NNI):m Private NNI (P-NNI)m Public NNI =Inter-Switching System Interface (ISSI)Intra-LATA ISSI (Regional Bell Operating Co)m Inter-LATA ISSI (Inter-exchange Carriers)⇒ Broadband Inter-Carrier Interface (B-ICI)q 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 Layersq The ATM Adaptation Layerm How to break messages to cellsq The ATM Layerm Transmission/Switching/Receptionm Congestion Control/Buffer managementm Cell header generation/removal atsource/destinationm Cell address translationm Sequential deliveryRaj JainThe Ohio State University117492Virtual Circuit SwitchingVirtual Circuit Switchingq Circuit Switching: bits coming on wire 4 go on wire 2q Virtual Circuit Switching: Cells coming on VCI=4 goon VCI=2Raj JainThe Ohio State University12Cell Header FormatCell Header Formatq GFC = Generic Flow Controlm (Was used in UNI but not in NNI)q 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)q 1 + x + x2 + x8q Protects header onlyq Optional Correction mode: Correct one bit errors if noearlier errorsq Discard cells with bad HECq Recalculated on each hopCorrectionModeDetectionModeErrorCorrect if possibleNo ErrorErrorNo ErrorRaj JainThe Ohio State University14Payload Type Field CodingPayload Type Field Codingq 000User data cell, no congestion, AAU = 0q 001User data cell, no congestion, AAU = 1q 010User data cell, congestion, AAU = 0q 011User data cell, congestion, AAU = 1q 100Segment Operation and management (OAM) cellq 101End-to-end OAM cellq 110Resource management cellq 111ReservedATM-user-to-ATM-user (AAU) bit available for user-to-user indicationRaj JainThe Ohio State University15Path vs ChannelsPath vs Channelsq 24/28-bit connection identifierFirst 8/12 bits: Virtual Path,Last 16 bits: Virtual Circuitq 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 ofOriginal Classes ofTrafficTrafficClass 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 5q Designed for data trafficq Less overhead bits than AAL 3/4⇒ Simple and Efficient AAL (SEAL)q No per cell length field, No per cell CRCPADUserPayloadLength CRC-32Control4220-64kB10PTI bit indicates last cell0-47Raj JainThe Ohio State University19AAL2AAL2q Ideal for low bit rate voiceq Variable/constant rate voiceq Multiple users per VCq Compression and Silence suppressionq Idle channel suppressionCellHeaderCellHeaderPayload 1PktHdrPayload 2 Payload 3PktHdrPktHdrPayload 1PktHdrPayload 2 Payload 3PktHdrPktHdrPayload 1 Payload 2 Payload 3Raj JainThe Ohio State University20Cell-Stream PhyCell-Stream Phyq Continuous stream of cells. No framing.q Hunt bit-by-bit for correct header.q Look for δ correct headers before entering synch stateq α incorrect headers ⇒ resynchronizeα and δ are parameters.CellHuntPresync SyncCorrect HECα Incorrect HECδ Correct HECsIncorrect HECRaj JainThe Ohio State University21SONETSONETq Synchronous optical networkq Standard for digital optical transmission(bit pipe)q Developed originally by Bellcore.Standardized by ANSI T1X1Standardized by CCITT ⇒ Synchronous Digital Hierarchy (SDH)q You can lease a SONET connection from carriersCity A City BCarriersRaj JainThe Ohio State University22Signal HierarchySignal HierarchyANSIDesignationOpticalSignalCCITTDesignationData Rate(Mbps)Payload Rate(Mbps)STS-1OC-151.8450.112STS-3OC-3STM-1155.52150.336STS-9OC-9STM-3466.56451.008STS-12 OC-12 STM-4 622.08


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WUSTL CIS 677 - ATM Networks: An Overview

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