现代通信网络课件4

现代通信网络ModernTelecommunicationNetworkLecture4PS分组交换与IP互联网北邮软件学院：陈候武[e-mail]电话：[phone]CommunicationNetworks【通信网络的分类】CommunicationNetworkSwitchedCommunicationNetworkVirtualCircuitNetwork:MPLSBroadcastCommunicationNetwork广播，电视，卫星PacketSwitch(PS)-分组交换DatagramNetwork:InternetCircuit-Switched(CS)-电话PS:PacketSwitch分组交换网原理SimpleSwitchedNetworkPacketSwitching(PS)PrinciplesCircuitswitchingdesignedforvoiceResourcesdedicatedtoaparticularcallMuchofthetimeadataconnectionisidleDatarateisfixedBothendsmustoperateatthesameratePS：BasicOperation【基本操作原理】DatatransmittedinsmallpacketsTypically1000octetsLongermessagessplitintoseriesofpacketsEachpacketcontainsaportionofuserdataplussomecontrolinfoControlinfo【控制信息】Routing(addressing)infoPacketsarereceived,storedbriefly(buffered)andpastontothenextnodeStoreandforwardPS：UsingPacketsPS：Advantages【优点】LineefficiencySinglenodetonodelinkcanbesharedbymanypacketsovertimePacketsqueuedandtransmittedasfastaspossibleDatarateconversionEachstationconnectstothelocalnodeatitsownspeedNodesbufferdataifrequiredtoequalizeratesPacketsareacceptedevenwhennetworkisbusyDeliverymayslowdownPrioritiescanbeusedPS：SwitchingTechnique【交换技术】StationbreakslongmessageintopacketsPacketssentoneatatimetothenetworkPacketshandledintwowaysDatagram【数据报】VirtualCircuit【虚电路】PVC:PermanentVirtualCircuit【永久虚电路】SVC:SwitchVirtualCircuit【交换虚电路】PS：Datagram【数据报】EachpackettreatedindependentlyPacketscantakeanypracticalroutePacketsmayarriveoutoforderPacketsmaygomissingUptoreceivertore-orderpacketsandrecoverfrommissingpacketsPS：DatagramApproachPS：VirtualCircuit【虚电路】PreplannedrouteestablishedbeforeanypacketssentCallrequestandcallacceptpacketsestablishconnection(handshake)EachpacketcontainsavirtualcircuitidentifierinsteadofdestinationaddressNoroutingdecisionsrequiredforeachpacketClearrequesttodropcircuitNotadedicatedpathSVC：SwitchVirtualCircuit–连接建立【可交换的虚电路】SVC：SwitchedVirtualCircuit–数据传输【可交换的虚电路】SVC：SwitchedVirtualCircuit–连接释放【可交换的虚电路】VirtualCircuitsvDatagramVirtualcircuitsNetworkcanprovidesequencinganderrorcontrolPacketsareforwardedmorequicklyNoroutingdecisionstomakeLessreliableLossofanodeloosesallcircuitsthroughthatnodeDatagramNocallsetupphaseBetteriffewpacketsMoreflexibleRoutingcanbeusedtoavoidcongestedpartsofthenetwork虚电路举例：FrameRelay【帧中继】DLCI(DataLinkConnectionIdentifier)-identificationofavirtualcircuit【虚电路】DLCI-oflocal(foragivenport)meaningtherecanbemax.976VCsonaninterfaceuser-networkDLCIvalues:0-LMIchannel,1-15-reserved,16-991-availableforVCs,992-1007-layer2managementofFRservice,1008-1022-reserved,1023-inchannellayermanagementABCToA:DLCI121ToB:DLCI243ToA:DLCI182ToC:DLCI121TimingofDatagramPacketSwitchingPacket3Packet3Packet1Packet2Packet1Packet2Packet1Packet2Packet3processingdelayofPacket1atNode2Host1Host2Node1Node2propagationdelaybetweenHost1andNode2transmissiontimeofPacket1atHost1三种交换的比较报文报文报文ABCDABCDABCD报文交换电路交换分组交换t连接建立数据传送报文连接释放数据传送的特点比特流直达终点报文报文报文分组分组分组存储转发存储转发存储转发存储转发【独享】–【共享】虚电路概念在TD-SCDMA网络：空间接口的应用3GPP-HSDPA概述为了更好地发展数据业务，3GPP对空中接口作了改进，在R5版本中引入高速下行分组接入（HSDPA）技术;HSDPA(高速下行分组接入，HighSpeedDownlinkPackagesAccess)技术，是3GPP在R5协议中为了满足上下行数据业务不对称的需求提出来的，它可以在不改变已经建设的系统网络结构的基础上，大大提高用户下行数据业务速率(理论上单载波最大值可达2.8Mbps)基站侧物理资源有限，HSDPA资源不可以同时分配给R4业务使用，比如，当系统为3个上行时隙与3个下行时隙的比例配置时，其中2个下行时隙分配给HSDPA使用，则下行业务时隙就剩下1个时隙，此时如果大量用户的业务需求是普通R4业务，则系统会受限于资源而决绝新用户的接入所以当业务小区内普通R4业务较多时，可以减少或者取消HSDPA资源配置，将大部分时隙资源分配给普通R4业务使用；当业务小区内大部分用户需要使用高速下载的数据业务，则可以将大部分业务时隙分配给HSDPA使用灵活的载波配置可以满足运营商网络规划中的不同的需求1.HSDPA载波配置TD-SCDMA无线帧结构2.物理层复用与调度算法用户被调度是HSDPA业务区别于普通R4业务的一个主要特征普通R4用户会【“独享”】一部分物理资源，直到其业务被释放掉，即使此时并没有在进行数据传输，资源也是被占用的，形成了一种浪费（类似：电路交换中的实电路）而HSDPA业务，可以让多用户【共享】整个HSDPA资源，采取的方式是分时分码复用，也就是在每一个TTI内部分或者全部资源为一个用户而用，下一个TTI，资源又给另一个用户使用，这样数据需求量大的用户就可以获得较高的被调用的几率，从而获得较高速率，节省了资源。灵活的调度算法也可以满足运营商不同的需求。PS应用：IP-Internet分组交换网-IP因特网7.1IP互联网结构InternetworkingTerms(1)CommunicationsNetworkFacilitythatprovidesdatatransferserviceTheInternet【因特网】-noteuppercaseITheglobalcollectionofthousandsofindividualmachinesandnetworksIntranet【内联网】CorporateinternetoperatingwithintheorganizationUsesInternet(TCP/IPandhttp)technologytodeliverdocumentsandresourcesTelecommuterResidentialCableInternetBackbonexDSL,FTTH,DialAggregationISP’sEnterpriseEnterpriseIP-InternetArchitectureTransportControlProtocol(TCP)InternetProtocol(IP)InternetworkingTerms-2EndSystem(ES)DeviceattachedtooneofthenetworksofaninternetSupportsend-userapplicationsorservicesIntermediateSystem(IS)DeviceusedtoconnecttwonetworksPermitscommunicationbetweenendsystemsattachedtodifferentnetworksInternetworkingTerms-3BridgeISusedtoconnecttwoLANsusingsimilarLANprotocolsAddressfilterpassingonpacketstotherequirednetworkonlyOSIlayer2(DataLink)RouterConnectstwo(possiblydissimilar)networksUsesinternetprotocolpresentineachrouterandendsystemOSILayer3(Network)USA-InternetInfrastructurelocalISPcampusnetworkcorporatenetworkIXPRegionalNetworkRegionalNetworklocalISPlocalISPIXPIXPBackboneNetworkBackboneNetworkRegionalNetworkRegionalNetworkInternetInfrastructure•Theinfrastr