3研究生—ATM-10-12.ppt

ATM的主要内容 ATM基础ATM信元 Cell ATM连接ATM地址ATMPVC s SVC s ATM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WAN Cells Voice Data Video ATM概貌 ATMSwitch LS1010 LS2020 LS100 ATMRouter C4500 4700 C7200 C7000 7500LANSwitchw ATMup link Cat5000 5500 Cat2820 Cat3x00ATMDXI HSSItoATM ALLCiscoroutersthatsupportHSSIinterface CES CircuitEmulation C7200 CES PA LS1010 ATMBasic UNI User to NetworkInterfaceNNI Network to NetworkInterfaceCellheadercontentvariesdependingonwho stalkingtowhom UNI UNI NNI NNI NNI ATMNetwork ATMNetwork 从分组到信元 Dest Address SourceAddress Data FrameCheck Payload Header Packet Cells Payload Header Payload Header Payload Header 5ByteHeader 48BytePayload ATMCell 53Bytes ATMCellHeader 5ByteHeader 48BytePayload ATMCell 53Bytes ATMCell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 1 User ControlData2 Congestion3 LastCellCLP信元丢失优先级HEC封装头检查和8BitCRC 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 S2 S6 S4 S7 VC S1 S8 S3 S5 ATM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 ATMPhysicalLinkVirtualChannelConnection VCC VirtualPath VP ContainsMultipleVCs VirtualChannelConnection VCC ContainsMultipleVPs VirtualChannel VC LogicalPathBetweenATMEndPoints VirtualChannels VC E3OC 12 VirtualPath VP VirtualPath VP 连结表示符 VPI VCI VirtualChannels VC ATMSwitches ATMswitches转变VPI VCI的值VPI VCI值对于某一端口是唯一的 不同交换机可以使用相同的VPI VCI值 4 5 2 9 6 4 2 9 2 9 4 5 6 4 2 9 1 2 1 3 4 5 2 9 2 9 6 4 2 1 3 1 VPI VCI Port VPI VCI Port Input Output AcellisswitchatVCorVPlevel VCSwitching SwitchreceiveacellwithaconfiguredVPIandVCI itlookupitsconnectiontabletodetermineoutgoingport orports withnewVPI VCIvalue VPSwitching SwitchreceiveacellwithknownVPIissendouttonewportwithnewVPvalue Port1 VPI2 VCI100 VCI110 Port2 VPI5 VCI110 Port3 VPI1 VCI50 Port4 VPI7 VCI100 VCI110 OR VPandVCSwitching VPandVCSwitching VCI1 VCI2 VCI3 VCI4 VPI2 VPI3 VPI1 VPI2 VPI3 VPI5 VPI1 VPI4 Port1 Port2 Port3 VCI1 VCI2 VCI1 VCI2 VPSwitch VCSwitch 20 VC和VP 信元中继的hop by hop转发过程 VirtualChannelConnection VCC VirtualPathConnection VPC VPSwitch VCSwitch VCSwitch NNI NNI VPI 2VCI 44 VPI 1VCI 1 VPI 26VCI 44 VPI 20VCI 30 UNI UNI ATMAddress DSP DomainSpecificPartESI EndSystemIdentifier MACAddress SEL Selector ICDATMFormat IDP IDI 20Bytes 6Bytes 12Digits 13Bytes 26Digits 1Byte Prefix ESI DSP ESI SEL AFI AuthorityandFormatIdentifier格式类型的说明ICD InternationalCodeDesignator国际编码设计者IDP InitialDomainPartIDI InitialDomainIdentifier 地址字段的分配 ATMAddress 47 0091 0000 0000 0000 0000 0000 1111 1111 1111 00 ATMPrefix MAC NA ATMaddressexample ATMaddress也称为NSAPaddress ATM地址管理 HereisMyMACAddress ESI 00c0 acdc 3124 efa8 WhatisMyATMPrefix HereisYourATMPrefix47 0090 ILMI自动配置ATMAddress ILMI IntegratedlocalManagementInterface ATMConnection PVCSVCSoftPVC SettingupATMVC 三种ATM连结 PVC PermanentVirtualConnections 手工静态配置SVC SwitchedVirtualConnections 一般是由信令协议自动建立 如LANE MPOA SoftPVC SVC和PVC的组合 PVC 手工配置 连接映射是静态的 无法重路由 SVC 使用信令建立 B D 1 2 4 1 3 3 2 4 1 2 C Input Output Port VPI VCI Port VPI VCI 1 64 3 29 3 29 1 64 Input Output Port VPI VCI Port VPI VCI 2 52 1 29 1 64 3 29 3 29 1 64 Input Output Port VPI VCI Port VPI VCI 1 29 3 45 1 64 3 29 3 29 1 64 Input Output Port VPI VCI Port VPI VCI 1 64 3 29 3 29 1 64 A 3 SVC 建立后传输数据 B D 1 2 4 1 3 3 2 4 1 2 C Input Output Port VPI VCI Port VPI VCI 1 64 3 29 3 29 1 64 Input Output Port VPI VCI Port VPI VCI 2 52 1 29 1 64 3 29 3 29 1 64 Input Output Port VPI VCI Port VPI VCI 1 29 3 45 1 64 3 29 3 29 1 64 Input Output Port VPI VCI Port VPI VCI 1 64 3 29 3 29 1 64 A 3 1 29 3 45 1 45 2 16 1 16 2 43 SVC 通过信令撤销连接 B D 1 2 4 1 3 3 2 4 1 2 C Input Output Port VPI VCI Port VPI VCI 1 64 3 29 3 29 1 64 Input Output Port VPI VCI Port VPI VCI 2 52 1 29 1 64 3 29 3 29 1 64 Input Output Port VPI VCI Port VPI VCI 1 29 3 45 1 64 3 29 3 29 1 64 Input Output Port VPI VCI Port VPI VCI 1 64 3 29 3 29 1 64 A 3 SoftPVC PVCestablishedmanuallyacrossUNIanddynamicallyacrossNNI B D 1 1 2 Input Output Port VPI VCI Port VPI VCI 1 64 3 29 3 29 1 64 Input Output Port VPI VCI Port VPI VCI 2 52 1 29 1 64 3 29 3 29 1 64 Input Output Port VPI VCI Port VPI VCI 1 29 3 45 1 64 3 29 3 29 1 64 Input Output Port VPI VCI Port VPI VCI 1 64 3 29 3 29 1 64 3 1 29 3 45 1 16 2 43 C A SettingupSVC 终端A连接到终端B需要一下过程 StationAsendacallsetuptotheStationB sATMaddressviasignalingchannel VPI VCI 0 5 Call setupsignalingisroutedthroughATMswitchestoStationB StationBacceptstheCall setuprequest send ACK backtoStationA ConnectionisestablishedOnce ACK isreceivedbyStationA aend to endcircuitisestablishedthroughATMnetwork VPI VCInumberisdynamicallyassignedbetweeneachhop Requirements 1 Addressing2 Signaling3 PathDetermination routing 3 5ATM的服务类别 在ATM网络中 端系统使用服务种类来表示所需的服务类型 ATM论坛定义过以下的服务种类 实时服务 恒定比特率 CBR 实时可变比特率 rt VBR 非实时服务 非实时可变比特率 nrt VBR 可用比特率 ABR 不指明比特率 UBR 恒定比特率 CBR CBR服务也许是最容易定义的服务 CBR用于支持这样的应用 它需要在整个连接持续期间具有连续可用的恒定数据率 并对传输时延有相对严格的上限要求 CBR通常用于未压缩声音和视像信息 其应用的例子包括 视频会议 videoconferencing 交互的声音 如电话 声音 视像分发 如电视 远程学习 收费电视 声音 视像度区 如点播视像 声音图书馆 实时可变比特率 rt VBR rt VBR服务是用于对时间敏感的应用 这类应用对于时延和时延抖动有严格的要求 适合于rt VBR的应用与适合于CBR的应用的主要不同之处是 rt VBR应用的传输速率会随时间变化 相同的 一个rt VBR信源具有突发性特征 Rt VBR服务比CBR服务允许网络有更大的灵活性 非实时可变比特率 nrt VBR 对于一些非实时的应用 可以通过描述通信流量特性从而使网络能够在丢失和时延方面提供服务质量的实质性改进 这些应用可以使用nrt VBR服务 对于这样的服务 端系统指明峰值信元速率 持续信元速率或平均信元速率 以及一个衡量信元突发性或密集程度的度量 利用这些信息 网络就能够分配资源以便提供相对地的时延和最小的信元丢失 nrt VBR服务能够用于具有严格时间响应要求的数据传输 不指明比特率 UBR 在任一给定时间 ATM网络的一部分容量用在承载CBR以及两类VBR的通信量上 由于一下一点或两点原因 网络会由一些富裕容量可用 1 并不是所有的资源都被用于CBR和VBR业务量 2 VBR业务量的突发性特征意味着有时实际使用的容量会少于分配到的容量 所有为使用的容量都可以供UBR使用 这种服务适合于能够容忍可变时延和一些信元丢失的应用 基于TCP的服务就是这种应用的典型 可用比特率 ABR 使用ABR的应用指明了一个它所使用的峰值信源速率PCR PeakCellRate 以及所需要的最小信源速率MCR MinimunCellRate 网络分配资源以便使得所有ABR应用都接受到的容量达到其MCR值 然后 任何未使用的容量都在全体ABR应用之间可公平的共享 ABR机制使用向信源发出显示反馈能确保公平的分配容量 ABR未使用的资源可供UBR服务使用 使用ABR应用的一个例子是局域网互连 ATM业务 数据 迄今为止的主流原因 宽带 快速的数据平台优势正在丧失 ATM业务 图像 VOD 优于IP 质量优于广播电视 双向优于普通电信电路 调度 广播 信令问题 范围不够广泛 3 6ATM的服务质量QoS Qualityofservice 服务质量对于ATM网络是一个非常重要的事项 其部分原因是因为它们用于诸如声频和视频这类实时交通 在建立一条虚电路时 端点用户 典型的是在主机中的一个进程 代表客户 和ATM网络层 代表网络运营者 或称载体部门 必须达成一个定义服务的协定 在公用网络的情况下 这个协定可以具有法律的效应 例如 如果载体部门同意信元丢失率不会超过每千兆位一个信元 而网络在实际运行过程中每千兆位丢失两个信元 那么客户就可以控告网络运营者违约 客户和网络之间的协定 1 将要提供的流量2 协定的服务3 答应的必要条件 服务质量参数 ATMLANEmulation Ethernet网的特点 无连接每个数据帧包都携带原地址和目的地址数据帧长度可变 最大可以达到bytes每个主机都有6 byteMACaddress ATM网的特点 面向连接的服务EstablishaVirtualChannelConnection VCC first thensenddataunitsovertheVCCFixeddataunitsize 53bytecellsEachATMhosthasa20 byteNSAPaddress UNISignaling Point to PointVCCSetup UNI UNI HostA HostB NSAPA NSAPB Switch1 Switch2 SetupCallProcConnectConnACK SetupCallProcConnectConnACK SetupCallProcConnectConnACK NNI SignalingChannelVPI VCI 0 5 Broadcast MulticastinEthernet AchievedbyspecificaddressesBroadcastaddressFF FF FF FF FF FFMulticastgroupscanbesetupwithaMulticastgroupaddress Broadcast MulticastinATM RootsendscallsetuptoLeaf1 Leaf3 Root Switch1 Switch2 Leaf1 Leaf2 Leaf4 Achievedbyaunidirectionalpoint to multipointVCC UNI Point to MultipointVCC RootsendsAddpartytoalltheremainingleaves Leaf3 Root Switch1 Switch2 Leaf1 Leaf2 Leaf4 InterimLayerManagementInterface ILMI AutoConfiguration UNI HostA ILMIChannelVPI VCI 0 16 AhasapreassignedEndStationIdentifier ESI 6bytes The13byteATMaddressprefixisobtainedfromtheATMswitchviaILMIILMIusestheSNMPrequest responsemechanismoverATM CreatingCellsfromFrames UserInformation UserInformation header Pad AAL5Trailer ATMhdr 5 Payload 48 UserHigherLayer AAL5Layer ATMLayer UserInformation EncapsulationHeader RFC1483 LANE ATMhdr 5 Payload 48 CellTax LastCellMarkedwithEOMBit IPoverEthernet Ethernet EachhosthasanIPaddressandaMACaddressAbroadcastsanARPforB sMACaddress MACaddress HostB MACaddress HostA IPaddress IPaddress ARPbroadcast FF FF FF FF FF FF IPA IPB MACA IPoverEthernet B sMACAddress AllstationslistentobroadcastsARPresponseisaunicastwithAasdestination MACaddress HostB MACaddress HostA IPaddress IPaddress Ethernet IPA IPB MACA MACB Ethernet KeyMechanisms ARP broadcastingandmulticasting 实现ATM仿真局域网面临的问题 Non BroadcastMultipleAccessfabric NBMA AddressresolutionBroadcastingConfiguration ATMNetwork LANE方法 LANEhidesATMfromthenetworklayerbyemulatinganEthernetorTokenRing HostB HostA IPAddress IPAddress ATMAddress ATMAddress LogicalIPSubnet Ethernet TokenRingLANEmulation EmulatingaLANoverATM Phy Phy Phy Phy Phy Phy ATM TCP ATM Host Router IP MAC SSCOP Q 2931 NNI Convg P NNI TCP IP MAC SSCOP Q 2931 SSCOP Q 2931 NNI Convg P NNI SSCOP Q 2931 ATMSwitch ATMSwitch ATM Host Router RFC1483 Encapsulation AAL5 AAL5 AAL5 RFC1483 Encapsulation AAL5 ATM Phy ATM Phy ATM Phy ATM Phy ATM Phy ATM Phy MAC MAC UNISignal ing ATMRouting P NNIProtocol VirtualLANs LANEmulation NativeModeRoutingProtocols NNISignal ing UNISignal ing EmulatingaLANoverATM Phy Phy Phy Phy Phy Phy ATM TCP ATM Host Router IP MAC SSCOP Q 2931 NNI Convg P NNI TCP IP MAC SSCOP Q 2931 SSCOP Q 2931 NNI Convg P NNI SSCOP Q 2931 ATMSwitch ATMSwitch ATM Host Router RFC1483 Encapsulation AAL5 AAL5 AAL5 RFC1483 Encapsulation AAL5 ATM Phy ATM Phy ATM Phy ATM Phy ATM Phy ATM Phy AddressresolutionbetweenMACaddressandATMaddress LE ARP MAC MAC UNISignal ing ATMRouting P NNIProtocol NativeModeRoutingProtocols NNISignal ing UNISignal ing VirtualLANs LANEmulation EmulatingaLANoverATM Phy Phy Phy Phy Phy Phy ATM TCP ATM Host Router IP SSCOP Q 2931 NNI Convg P NNI TCP IP SSCOP Q 2931 SSCOP Q 2931 NNI Convg P NNI SSCOP Q 2931 ATMSwitch ATMSwitch ATM Host Router RFC1483 Encapsulation AAL5 AAL5 AAL5 RFC1483 Encapsulation AAL5 ATM Phy ATM Phy ATM Phy ATM Phy ATM Phy ATM Phy UNISignal ing ATMRouting P NNIProtocol NativeModeRoutingProtocols NNISignal ing UNISignal ing SupportMAClayerbroadcastingoveranATMFabric MAC MAC VirtualLANs LANEmulation EmulatingaLANoverATM Addressresolutionachievedwithanaddressresolutionserver ATMattachedhostsrunningLANEaretheclientsEachLANEhostregistersitsMAC ATMtuplewiththeLES HostA IPAddress ATMAddress HostB IPAddress ATMAddress LogicalIPSubnet LANEmulationServer MACAddress MACAddress LANEmulation EmulatingaLANoverATM BroadcastsareachievedbyausingabroadcastserverThebroadcastserverisresponsibleforserializingbroadcastsfrommultiplehosts HostA IPAddress ATMAddress HostB IPAddress ATMAddress LANEmulation LogicalIPSubnet BroadcastServer MACAddress MACAddress LANEmulation LANEmulationUNI LUNI LANEmulationClient LEC LANEConfigurationServer LECS LANEmulationServer LES BroadcastandUnknownServer BUS LANEmulationClient LEC LES LECS BUS LEC LEC EmulatedLAN AnemulatedLANisabroadcastdomain e g IPsubnet AnELANconsistsofatleastoneLES BUSandmultipleLECsEachELANcanemulateeitherEthernetorTokenRing LEC LEC LEC LEC LES LECS BUS HostA HostB LANEmulationClient LEC Performsdataforwarding belongstoasingleemulatedLANPerformsaddressresolutionfromMACaddresstoATMaddress LE ARP Datatransfer LEC LEC LEC LEC LES LECS BUS LE ARP HostA HostB TheFirstStepforanLEC LEC LEC LEC LES LECS HostA HostB ILMIChannelVPI VCI 0 16 WhatistheLECSaddress TheLECgetstheLECSaddressfromtheATMswitchAllATMswitchesneedtohavethesamesetofLECSaddressesconfiguredinthesameorder TheFirstStepforanLEC LEC LEC LEC LEC LES LECS BUS HostA HostB LECSwell knownaddress 47 007900000000000000000000 00A03E000001 00 TheLECmayalsousethewell knownLECSaddressorapreconfiguredLECSaddress LANEConfigurationServer LECS LEC LEC LEC LEC LES LECS BUS IwouldliketojoinELANred ConfigureDirectVCC HostA HostB TheLECSprovidesaccesscontroltoalltheELANsandisastartingpointforeachLECTheCONFIGUREDIRECTVCCisusedforprovidingconfigurationinformationtoeachLEC HostA HostB LANEConfigurationServer LECS TheCiscoLECShasadatabasekeyedontheATMaddressofaLEC MACaddressofalegacyLANdestinationortheELANname LEC LEC LEC LEC LES LECS BUS OK TheLESaddressforELANredisABCDE ConfigureDirectVCC redABCDE blueEFGHI HostA HostB TheLEShasultimatecontroloverwhojoinstheELANItprovidesaregistrationfacilityforLECstoregisterMACaddressesand orTokenRingsourcedescriptors LANEmulationServer LES LEC LEC LEC LEC LES LECS BUS Iwouldliketojoin MyMACaddressisB ControlDirectVCC TheCiscoLEScrosschecksthejoiningLEC seligibilitytojoinitsELANwiththeLECSdatabase LANEmulationServer LES LEC LEC LEC LEC LES LECS BUS OK YourLECIDis4 ControlDirectVCC HostA HostB LANEmulationServer LES LEShandlesLE ARPstoresolveMACaddressestoATMaddresses LEC LEC LEC LEC LES LECS BUS ControlDirectVCC LE ARPRequest WhatisB sATMaddress LE ARP HostA HostB LANEmulationServer LES LEShandlesLE ARPstoresolveMACaddressestoATMaddresses LEC LEC LEC LEC LES LECS BUS ControlDirectVCC LE ARPResponse B sATMAddress LE ARP HostA HostB LANEmulationServer LES LEC LEC LEC LEC LES LECS BUS ControlDirectVCC LE ARPRequest WhatisC ATMaddress LE ARP HostC AllMACaddressesinELANneednotberegisteredwiththeLESEspeciallytrueforMACaddressesbehindproxyLECs HostA HostB LANEmulationServer LES TheControlDistributeVCCisusedforforwardingunresolvedLE ARPrequeststoalltheLECsintheELAN LEC LEC LEC LEC LES LECS BUS ControlDistributeVCC LE ARP HostC HostA HostB BroadcastandUnknownServer BUS BUShandlesbroadcast multicasttrafficandunicastfloodingforunresolved unknown addressesTheLECsendsallbroadcastsalongtheMulticastSendVCC LEC LEC LEC LEC LES LECS BUS MulticastSendVCC BroadcastSAPupdate HostA HostB BroadcastandUnknownServer Cont LEC LEC LE