文档介绍：ATM的主要内容ATM基础ATM信元(Cell)ATM连接ATM地址ATMPVC’s&SVC’sATM的特点使用小的、固定尺寸的信元面向连接支持多种服务类型可用于LAN和WANCellsVoiceDataVideoATM概貌ATMSwitch-LS1010,LS2020,-C4500/4700,C7200,C7000/7500LANSwitchw/ATMup-link-Cat5000/5500,Cat2820,Cat3x00ATMDXI(HSSItoATM)-(CircuitEmulation)-C7200(CES-PA),workPBXPBXHSSIADSURouterATMSwitchLANSwitchATMBasicUNI=User-work-workInterfaceCellheadercontentvariesdepending onwho’work从分组到信元Dest. AddressSource AddressDataFrame CheckPayloadHeaderPacketCellsPayloadHeaderPayloadHeaderPayloadHeader5Byte Header48Byte PayloadATMCell53 BytesATMCellHeader5Byte Header48Byte PayloadATMCell53BytesATMCell格式GFC 一般流量控制 VPI/VCI 虚通道/虚通路标识PTI 负载类型 3Bits: 信元丢失优先级HEC 封装头检查和 8BitCRCATMUNICell48Byte PayloadGFC(4)VPI(8)VCI(16)PTICLPHECATMNNICell48Byte PayloadVPI(12)VCI(16)PTICLPHEC连结类型无连结:PacketRoutingPath1=S1,S2,S6,S8Path2=S1,S4,S7,S8数据可以选取不同的路径,分组可能出现失序面向连结:CellSwitchingVC=S1,S4,S7,S8数据使用同一路径传输,按序到达S2S6S4S7S3S5S1S8111222S2S6S4S7VCS1S8S3S5ATM要点Connectionoriented–虚电路必须在数据传输之前事先建立每一条虚电路同时一组VPI和VCI标示虚通道可以包含一组虚通路VPI和VCI仅有当地的意义虚通路和虚通道ATMPhysicalLink VirtualChannelConnection(VCC)VirtualPath (VP) ContainsMultipleVCsVirtualChannelConnection (VCC) ContainsMultipleVPsVirtualChannel (VC) LogicalPath BetweenATMEndPointsVirtualChannels(VC)E3 OC–12VirtualPath(VP)VirtualPath(VP)连结表示符=VPI/VCIVirtualChannels(VC)