21-1©2005 Raj JainCSE473sWashington University in St. LouisATM Networks: ATM Networks: An OverviewAn OverviewRaj Jain Washington UniversitySaint Louis, MO [email protected] slides are available on-line at:http://www.cse.wustl.edu/~jain/cse473-05/21-2©2005 Raj JainCSE473sWashington University in St. Louisq ATM vs Phone Networks and Data Networksq ATM Protocol Layersq Cell Header Format, AALs q Physical Media q Service Classes: CBR, VBR,ABR, UBR, GFROverviewOverview21-3©2005 Raj JainCSE473sWashington University in St. LouisATMATMq ATM Net = Data Net + Phone Netq Combination of Internet method of communication (packet switching) and phone companies’ method (circuit switching)ATM21-4©2005 Raj JainCSE473sWashington University in St. LouisATM vs Phone NetworksATM vs Phone Networksq Legacy 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 circuits are manually setup. ATM allows automated setup.125 μs21-5©2005 Raj JainCSE473sWashington University in St. LouisATM vs Data NetworksATM vs Data Networksq Signaling: Internet Protocol (IP) was connectionless.You could not 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 and processed individually. q Traffic Management: Loss based in IP.ATM has newer traffic management technology.Required for high-speed and variable demands.q Cells: Fixed size or small size. Not important21-7©2005 Raj JainCSE473sWashington University in St. LouisPrivateNNIPrivateUNIATM InterfacesATM InterfacesComputerPrivateSwitchPublicSwitchRouterDigitalServiceUnitDXIB-ICIPublicUNIPublicNNIPrivateUNIPrivateSwitchPublicSwitchCarriersPublicSwitchCarrierComputer21-8©2005 Raj JainCSE473sWashington University in St. LouisATM InterfacesATM Interfacesq User to Network Interface (UNI): Public UNI, Private UNIq Network to Node Interface (NNI): q Private NNI (P-NNI)q Public NNI =Inter-Switching System Interface (ISSI)Intra-LATA ISSI (Regional Bell Operating Co)q 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)21-9©2005 Raj JainCSE473sWashington University in St. LouisATM LayerATM Adaptation LayerPhysicalLayerATM LayerPhysicalLayerATM LayerATM Adaptation LayerPhysicalLayerEnd SystemSwitchProtocol LayersProtocol LayersHigherLayerEnd SystemHigherLayer21-10©2005 Raj JainCSE473sWashington University in St. LouisProtocol LayersProtocol Layersq The ATM Adaptation Layerq How to break messages to cellsq The ATM Layerq Transmission/Switching/Receptionq Congestion Control/Buffer managementq Cell header generation/removal at source/destinationq Cell address translationq Sequential delivery21-11©2005 Raj JainCSE473sWashington University in St. LouisVirtual Circuit NumbersVirtual Circuit Numbersq Each cell has a circuit numberq Circuit number determines the cell’s queuing and forwardingq Circuits have be set up before useq Circuits are called Virtual Circuits (VCs)PBXPBXPBXPBX1 3 5 2 321-12©2005 Raj JainCSE473sWashington University in St. LouisCell Header FormatCell Header Formatq GFC = Generic Flow Controlq (Was used in UNI but not in NNI)q VPI/VCI = 0/0 ⇒ Idle cell; 0/n ⇒ Signalingq HEC: 1 + x + x2+ x8VCI PTIHeader Error Check (HEC)VCIVPI VCIGFC/VPI VPICLPPayload21-13©2005 Raj JainCSE473sWashington University in St. LouisPath 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 carriersVC1VC2VC3VC1VC2VC3VC1VC2VC3VP1VP2VP3Link21-14©2005 Raj JainCSE473sWashington University in St. LouisVP/VC Assignment/UseVP/VC Assignment/UseSwitch33 56Video Data37 34VoiceData213453556657661122Port0/370/340/330/56VPI/VCIIn1/350/560/654/76VPI/VCI3456PortOut21-15©2005 Raj JainCSE473sWashington University in St. LouisHeader Error ControlHeader Error Controlq 8 bit error control fieldq Calculated on remaining 32 bits of headerq Allows some error correction21-16©2005 Raj JainCSE473sWashington University in St. LouisHEC Operation at ReceiverHEC Operation at ReceiverCorrectionModeDetectionModeMultibit error detected(Cell discarded)Single-bit error detected(correction)No errordetectedError detected(cell discarded)No Errordetected21-17©2005 Raj JainCSE473sWashington University in St. LouisOriginal Classes of TrafficOriginal Classes of TrafficClass 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 AAL421-18©2005 Raj JainCSE473sWashington University in St. LouisAAL 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 cell0-4721-19©2005 Raj JainCSE473sWashington University in St. LouisAAL2AAL2q 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 321-20©2005 Raj JainCSE473sWashington University in St. LouisPhysical MediaPhysical Mediaq Multimode Fiber: 100 Mbps using 4b/5b, 155 Mbps SONET STS-3c, 155 Mbps 8b/10bq Single-mode Fiber: 155 Mbps STS-3c, 622 Mbpsq Plastic Optical Fiber: 155 Mbpsq Shielded Twisted Pair (STP): 155 Mbps 8b/10bq Coax: 45 Mbps, DS3, 155 Mbpsq Unshielded Twisted Pair (UTP)q UTP-3 (phone wire) at 25.6, 51.84, 155 Mbpsq UTP-5 (Data grade UTP) at 155 Mbpsq DS1, DS3, STS-3c, STM-1, E1, E3, J2, n × T121-22©2005 Raj JainCSE473sWashington University in St. LouisClasses of ServiceClasses of Serviceq ABR (Available bit rate): Source follows network feedback. Max throughput with minimum loss. q UBR (Unspecified bit rate): User sends whenever it wants. No feedback. No guarantee. Cells may be dropped during congestion.q CBR (Constant bit rate): User declares required rate.Throughput, delay and delay variation