现代通信网络课件

现代通信网络

ModernTelecommunicationNetworkLecture3(CS)电路交换与软交换北邮软件学院：陈候武Chenhouwu@电话：现代通信网络

ModernTelecommunicatio1CommunicationNetworks【通信网络的分类】CommunicationNetworkSwitched

CommunicationNetworkVirtualCircuitNetwork:MPLSBroadcast

CommunicationNetwork广播，电视，卫星PacketSwitch(PS)-分组交换DatagramNetwork:Internet:IP因特网Circuit-Switched(CS)-电话CommunicationNetworks【通信网络的分2通信业务网(ServiceNetwork)：分类：通信业务网(ServiceNetwork)：分类：3SwitchedNetwork：【通信交换网络】SwitchedNetwork：【通信交换网络】4NodeSwitching（节点交换）Anode(switch)inacircuitswitchingnetworkincominglinksoutgoinglinksNodeNodeSwitching（节点交换）Anode(5Nodes

【交换节点】Nodesmayconnecttoothernodesonly,ortostationsandothernodesNodetonodelinksusuallymultiplexed【复用】NetworkisusuallypartiallyconnectedSomeredundantconnections【冗余连接

】aredesirableforreliabilityTwodifferentswitchingtechnologiesCircuitswitching【电路交换】Packetswitching【分组交换】Nodes【交换节点】Nodesmayconnect6CS:CircuitSwitch电路交换【Overview】CS:CircuitSwitch7CS:CircuitSwitching【电路交换】Dedicatedcommunicationpathbetweentwostations【专用/独享的通信通道】Threephases【呼叫建立：3个阶段】EstablishTransferDisconnectMusthaveswitchingcapacityandchannelcapacitytoestablishconnectionMusthaveintelligencetoworkoutrouting必须具有智能以对呼叫进行选路CS:CircuitSwitching【电路交换】De8CircuitSwitching-ApplicationsInefficientChannelcapacitydedicatedfordurationofconnectionIfnodata,capacitywastedSetup(connection)takestimeOnceconnected,transferistransparentDevelopedforvoicetraffic(phone:电话网)CircuitSwitching-Applicatio9CS：PSTN–

网络结构PSTN–PublicSwitchedTelephoneNetworkUsesdigitaltrunksbetweenCentralOfficeswitches(CO)UsesanaloglinefromphonestoCODigitalTrunks数字中继AnaloglineCentralOfficeCentralOfficeCS：PSTN–网络结构PSTN–PublicSw10PSTN:PublicCircuitSwitchedNetworkPSTN:PublicCircuitSwitched11CS:Components【网络组成】Subscriber【用户：电话】Devicesattachedtonetwork

Subscriberline【用户连线】LocalLoop【本地环路】Subscriberloop【用户环路】ConnectiontonetworkFewkmuptofewtensofkmExchange/Switch【交换机】SwitchingcentersEndoffice-supportssubscribersTrunks【中继线】BranchesbetweenexchangesMultiplexed【复用】CS:Components【网络组成】Subscribe12LegacyDigitalCircuitSwitchCentralizedIntelligenceProprietaryCodeProprietaryservicedeploymentVeryexpensiveLegacyDigitalCircuitSwitchC13CircuitSwitchElements【电路交换组成】CircuitSwitchElements【电路交换组14CircuitSwitchingConceptsDigitalSwitch【数字交换】ProvidetransparentsignalpathbetweendevicesNetworkInterface【网络接口】ControlUnit【控制单元】EstablishconnectionsGenerallyondemandHandleandacknowledgerequestsDetermineifdestinationisfreeconstructpathMaintainconnectionDisconnectCircuitSwitchingConceptsDigi15NodeswitchingSystem:NodeswitchingSystem:16CS：SPC:电话数字程控交换机–模块CS：SPC:电话数字程控交换机–模块17CS:CirtuitSwitch

【SwitchFabric：交换矩阵】现代通信网络课件18SwitchFabric:MxNSwitchFabric:MxN19SwitchFabric:MathgraphpresentationAinputmaysetuponeconnection(1,3,6,7),multipleconnections(4),ornoconnection(2,5,8).SwitchFabric:Mathgraphpres20SwitchFabric:数学模型Inputset:T={0,1,2,…,M-1}Outputset:R={0,1,2,…,N-1}Definition:t∈Tandr∈Rt，Rt∈R，then:c=|t,Rt|isaconnection.tisstartpointoftheconnection,r∈Rtistheendpoint.ifr∈Rt,Rtcontainsonlyoneitem,thisconnectionispointtopoint.ifr∈Rt,Rtcontainsmorethanoneitem,thisconnectionispointtomulti-point.Multicast:Rt≠R;Broadcast:Rt=Rconnectionsetinswitchfabric:C=|c0,c1,c2,…|SwitchFabric:数学模型Inputset:21SwitchFabric:连接函数连接函数:inputlink:x(0<=x<=M-1)Outputlinkf(x)(0<=f(x)<=N-1).

例如：连接函数:δ(x2,x1,x0)=x1,x0,x2δ(000)=000,δ(001)=010,δ(010)=100,δ(111)=111SwitchFabric:连接函数连接函数:inpu22SwitchingFabric:TimeDivisionTime-slotswitchingisadevice,whichbuffersmincomingtime-slots,arrangesnewtransmitorderandtransmitsntime-slotsUsedinPacketswitchandATMaswellasdigitaltelephoneswitchSwitchingFabric:TimeDivisio23SwitchingFabric:SpaceDivisionSwitchingFabric:SpaceDivisi24Time/SpaceDivisionMultiplexing

TIMESWITCHTIMESWITCHTIMESWITCHTIMESWITCHTIMESWITCHTIMESWITCHSPACESWITCHTime/SpaceDivisionMultiplexi25CS：BlockingorNon-blockingBlocking【阻塞】AnetworkisunabletoconnectstationsbecauseallpathsareinuseAblockingnetworkallowsthis【网络允许Blocking】UsedonvoicesystemsShortdurationcallsNon-blocking【无阻塞】Permitsallstationstoconnect(inpairs)atonceUsedforsomedataconnectionsCS：BlockingorNon-blockingBlo26SwitchingFabric:Blocking如果：I0正在连续到O0,问：I1可以连接到O0orO1???结果：内部阻塞SwitchingFabric:Blocking如果：27解决方案：MultistageSwitchReducednumberofcross

pointsMorethanonepaththroughnetwork

IncreasedreliabilityMorecomplexcontrolMaybeblocking解决方案：MultistageSwitchReduced28解决方案：两级交换矩阵解决方案：两级交换矩阵29解决方案：ThreeStageSwitchxxxx解决方案：ThreeStageSwitchxxxx30CS：TST交换矩阵-实例：TST-TimeswitchandSpaceswitch(1)T接线器:Auserinfo.Occupyatimeslot8bitscode.CS：TST交换矩阵-实例：TST-Timesw31（3）TST接线器－512x512TimeSlots（3）TST接线器－512x512TimeSlo32CS:电路交换【PSTN:TrunkMultiplexing】现代通信网络课件33CO1–CO2:TruckMultiplexingCO1–CO2:TruckMultiplexing34Mux….….….….….11111222….64kb/svoicechannelt4t3t2t12Mb/soutputsignal同步时分复用：SynchronousTDMMux….….….….….11111222….64kb/s35E1:2Mb/sframestructureAllTimeslotscontain8bitwords(PCM,Data,Subrate,nx64kb/s)NetworkSignaling-CASorCCS0123…14151617…30310…1frame-256bits-125msFrameAlignmentWord3.9usNetworkSignalingChannels1to15Channels16to30E1:2Mb/sframestructureAllT36

MUXMUXMUXMUXMUX1234

1234

E1E1E1E1E2E2E2E2

E52.0488.44834.368139.264561.480MbpsMbpsMbpsMbpsMbps

CH2

CH1

CH32E31E32E33E34

E41E42E43E44ITU-TE1DIGITALMULTIPLEXINGHIERARCHYE1 E2E3E4E51E1E52.04837ANSI：T1-T-carriersystem1.544MEachframecarriesonesample(8bits)foreach24channels,plusoneframingbit=193bits193*8000(samples/sec)=1.544Mbit/sec=T-1Channel1Channel2Channel3Channel24…Channel1Channel2Channel3Channel24…FramingBit1D4FrameTDMANSI：T1-T-carriersystem1.538ANSI:T1/DS1FrameStructure-1.544Mbps

Every8thbitusedforsignalinginefficient01221226…2023…1frame-193bits-24channelsBit8-reservedforsignalingFramingbit34501Bits1-7PayloadANSI:T1/DS1FrameStructure39ANSI:DIGITALMULTIPLEXINGHIERARCHYT1 T2 T3T4T5

MUXMUXMUXMUXMUX12T313T324T335T346T357T36123412

T1T1T1T1T2T2T2T2T2T2T2

T4T4T5

CH1CH2CH2424VF1.5446.31244.736274.176560.160MbpsMbpsMbpsMbpsMbpsANSI:DIGITALMULTIPLEXING40现代通信网络课件41StatisticalTDM【统计时分复用】InSynchronousTDMmanyslotsarewastedStatisticalTDMallocatestimeslotsdynamicallybasedondemandMultiplexerscansinputlinesandcollectsdatauntilframefullDatarateonlinelowerthanaggregateratesofinputlinesStatisticalTDM【统计时分复用】InSyn42StatisticalTDMFrameFormatsStatisticalTDMFrameFormats43StatisticalTDMvSynchronousTDM

StatisticsTDMdividesadatalinkintosomelogicsub-channelStatisticalTDMvSynchronous44StatisticalTDMvSynchronousTDM：FormatsStatisticalTDMvSynchronous45StatisticalTDM举例：HDLCHDLC：HighLevelDataLinkControlSynchronoustransmissionAlltransmissionsinframesSingleframeformatforalldataandcontrolexchangesStatisticalTDM举例：HDLCHDLC：H46HDLC：FrameStructureFlagAddressControlInformationFCSFlag8bits8extendable8/16variable816/32trailerFrameCheckSumHDLC：FrameStructureFlagAddre47HDLC：AddressFieldIdentifiessecondarystationthatsentorwillreceiveframeUsually8bitslongMaybeextendedtomultiplesof7bitsLSBofeachoctetindicatesthatitisthelastoctet(1)ornot(0)Allones(11111111)isbroadcastHDLC：AddressFieldIdentifiess48CS:电路交换【PSTN:Signaling信令】与【CallControl：呼叫控制】CS:电路交换49CS:PSTN控制信令与呼叫控制–各阶段Eachconversationrequiresachannelswitchedthroughoutthenetwork呼叫请求：Callrequest；呼叫建立：Callestablished;呼叫接收1.Callisrequested3.Channelisestablished2.CallisacceptedCS:PSTN控制信令与呼叫控制–各阶段Each50PSTNCS:PSTN–

电话号码编码方案3digitsareacode【区域码】+3digitsofficecode【局码】+4digitsphone【本局随机码】EachLocalExchangeCarrierswitch(LEC：本地交换局)areassignedablockofatleast10,000numbersTheInter-ExchangeCarrier(IXC：汇接局)switchesareresponsiblefortransmittinglongdistanceIXC212LEC5554210(212)5554210PSTNCS:PSTN–电话号码编码方案3digit51CS:PSTN–CallRouting-1InternationalNumberingPlan–E.164【国际电话号码方案】useprefix-baseddialing4085644555212PSTN1+212+555+5644SS7CS:PSTN–CallRouting-1Int52CS:PSTN–CallRouting-2ThefirstLEC【本地交换机】receivesacall,seeing‘1’asthefirstdigitandthenpassesthecallontotheIXCswitch.TheIXCthenroutesthecall,viaSS7,totheremoteIXCresponsiblefor‘212’.【远端的212中继局】The‘212’IXClooksattheofficecodeandpassesitontothe‘555’LECswitch.【515本地局】The‘555’LECswitchthenchecksthestationcodeandsignalstheappropriatephoneCS:PSTN–CallRouting-2The53Signaling:ControlFunctions【控制功能】AudiblecommunicationwithsubscriberTransmissionofdialednumberCallcannotbecompletedindicationCallendedindicationSignaltoringphoneBillinginfoEquipmentandtrunkstatusinfoDiagnosticinfoControlofspecialistequipmentSignaling:ControlFunctions【54PSTN：用户信令Usesloop-startsignaling【环路信令】Indicatesifthephoneison-hookoroff-hook,orgeneratesring-toneonphone.Closescircuitwhenphoneisoff-hookUsestwowires,tipandringTipFXSRingPSTN：用户信令Usesloop-startsigna55SwitchtoSwitchSignaling：【中继信令】SubscribersconnectedtodifferentswitchesOriginatingswitchseizesinterswitchtrunkSendoffhooksignalontrunk,requestingdigitregisterattargetswitch(foraddress)Terminatingswitchsendsoffhookfollowedbyonhook(wink)toshowregisterreadyOriginatingswitchsendsaddressSwitchtoSwitchSignaling：【中继56中继信令：基本呼叫流程：中继信令：基本呼叫流程：57中继信令：呼叫控制：FSM–FiniteStateMachine

(有限状态机–

主叫方

)挂机状态摘机状态通话状态拨号状态忙音状态振铃状态请求呼叫状态回铃状态摘机拨号拨号正确拨号拨号错误被叫振铃被叫摘机被叫用户忙被叫无应答被叫挂机主叫挂机收到新的呼叫摘机中继信令：呼叫控制：FSM–FiniteStateM58PSTN:SignalingMethods【中继信令分类】CAS–ChannelAssociatedSignaling【随路信令】SignalingassociatedwitheachchannelhasfixedplacementwithinframeTraditionalT-1andE-1forvoiceusesCASCCS–CommonChannelSignaling【共路信令】Signalingpassedviamessagingprotocol,out-of-bandsignalingCancarryawidevarietyofmessages,e.g.Caller-IDetcISDNusesaCCS-basedprotocol–Q.931Q.SIGwhichistypicallyusedforPBX-to-PBXconnectivity,andisavariantofQ.931,isCCD-basedSS7istheCCS-basedprotocolusedinthePSTN,i.e.betweenCOsPSTN:SignalingMethods【中继信令分类59Drawbacks【缺点】ofInCASLimitedtransferrateDelaybetweenenteringaddress(dialing)andconnectionOvercomebyuseofcommonchannelsignalingDrawbacks【缺点】ofInCASLimited60CASv.CCSCASv.CCS61SS7：SignalingSystemNumber7SS7：CommonchannelsignalingschemeISDNOptimizedfor64kdigitalchannelnetworkCallcontrol,remotecontrol,managementandmaintenanceReliablemeansoftransferofinfoinsequenceWilloperateoveranalogandbelow64kPointtopointterrestrialandsatellitelinksSS7：SignalingSystemNumber7S62PSTN–SS7/SignalingSystem7SS7messagesareexchangedbetweennetworkelementsonbi-directionalchannels(typicallyT1lines)calledsignalinglinks.TrunkLinesSSP(CO)SSP(CO)STPSS7STPT-1T-1PSTN–SS7/SignalingSystem763PSTN–SS7SignalingPoints

SS7networkiscriticaltocallprocessing,SCPsandSTPsareusuallydeployedinmatedpairconfigurationsinseparatephysicallocationstoensurenetwork-wideserviceintheeventofanisolatedfailure.Linksbetweensignalingpointsarealsoprovisionedinpairs.Trafficissharedacrossalllinksinthelinkset.Ifoneofthelinksfails,thesignalingtrafficisreroutedoveranotherlinkinthelinkset.SS7LinksSTPSTPSSPSSPSCPSCPSS7LinksTrunkLinksPSTN–SS7SignalingPointsS64SS7：网元功能SSP(ServiceSwitchingPoint)

SSPsareswitchesthatoriginate,terminate,ortandemcalls.AnSSPsendssignalingmessagestootherSSPstosetup,manage,andreleasevoicecircuitsrequiredtocompleteacall.AnSSPmayalsosendaquerymessagetoaSCPtodeterminehowtorouteacall.【智能网功能】ThefunctionalityoftheSSPisusuallyintegratedintotheCO(CentralOfficeswitch：终端局).STP(SignalTransferPoint)【信号转接点】NetworktrafficbetweensignalingpointsmayberoutedviaapacketswitchcalledanSTP.AnSTProuteseachincomingmessagetoanoutgoingsignalinglinkbasedonroutinginformationcontainedintheSS7message.AnSTPcanalsoactasa"firewall"toscreenSS7messagesexchangedwithothernetworks.SCP(ServiceControlPoint)【信号控制点】AnSCPisacentralizeddatabasethattellsanSSPhowtorouteacall(e.g.,atoll-free1-800/888call).ItsendsaresponsetotheoriginatingSSPcontainingtheroutingnumber(s)associatedwiththedialednumber.SS7：网元功能SSP(ServiceSwitching65SS7：信令功能SS7在移动网络中漫游功能的应用SS7：信令功能SS7在移动网络中漫游功能的应用66CS:电路交换【PSTN:电话网组网原理】现代通信网络课件67CS：AT&TTelephonyHierarchyClass5Class4Class3Class2Class1CS：AT&TTelephonyHierarchyCla68CS：TelephoneNetworkModelCS：TelephoneNetworkModel69CS：传统电话网分层结构的问题：层次太多汇接层次（转接交换机）过多导致呼叫建立延迟传输损失。降低了呼叫接通率降低了系统的可靠性一个转接交换机出问题，将阻塞整个网络网络管理复杂CS：传统电话网分层结构的问题：层次太多70我国电话网：Twolevelsoftransitnetwork

长途网络结构正在从4层演进到2层（扁平化）DC1(directconnection1)–高层（省间层）DC2(directconnection2)–低层（省内层）我国电话网：Twolevelsoftransitne71CS：局间中继联系方式DC1–省际：互联至其他省；省内：星型连接至DC2DC2–同层DC2之间互联，或者部分互联，也可直连至其他省CS：局间中继联系方式DC1–省际：互联至其他省；省内：72CS：本地网互联方式Alllocalswitchesareconnectedeachotherbydirecttrucks.Suitabletolesslocalswitchesinthesamearea.CS：本地网互联方式Alllocalswitchesa73CS:电话网的路由选择高效直达路由(H):永远是首选低呼损直达路由(L):最后选择用户A–呼叫–用户B：A1-B1,A1-B2-B1,A1-A2-B2-B1,A1-A2-B3-B2-B1,A1-A2-A3-B3-B2-B1CS:电话网的路由选择高效直达路由(H):永远是首选74CS：Routing【电路交换：路由定义】ManyconnectionswillneedpathsthroughmorethanoneswitchNeedtofindarouteEfficiencyResilience【弹性】PublictelephoneswitchesareatreestructureStaticroutingusesthesameapproachallthetime【静态路由】Dynamicroutingallowsforchangesinroutingdependingontraffic【动态路由】UsesapeerstructurefornodesCS：Routing【电路交换：路由定义】Manyco75CS：AlternateRouting【迂回路由】PossibleroutesbetweenendofficespredefinedOriginatingswitchselectsappropriaterouteRouteslistedinpreferenceorderDifferentsetsofroutesmaybeusedatdifferenttimesCS：AlternateRouting【迂回路由】Pos76CS：Alternate

Routing

DiagramCS：AlternateRoutingDiagram77CS:电路交换【SoftSwitch:软交换】现代通信网络课件78CS存在问题：解决方案SoftswitchCS存在问题：解决方案Softswitch79Soft-switch：优点Generalpurpose:computerrunningsoftwaretomakeitasmartphoneswitchLowercostsGreaterfunctionalityPacketizingofdigitizedvoicedataAllowingvoiceoverIPMostcomplexpartoftelephonenetworkswitchis【softwarecontrollingcallprocess】CallroutingCallprocessinglogicTypicallyrunningonproprietaryprocessorSeparatecallprocessingfromhardwarefunctionofswitchPhysicalswitchingdonebymediagatewayCallprocessingdonebymediagatewaycontroller【softswitch】Soft-switch：优点Generalpurpose80TraditionalCircuitSwitchingTraditionalCircuitSwitching81CS：Softswitch

【软交换结构】MediaGatewayController【媒体网关控制器】=Softswitch：软交换CS：Softswitch【软交换结构】MediaGat82CS：软交换系统与传统设备区别

电路交换模型呼叫控制SS7

LineCardTrunkCardTimeSlot交换TDMTDM管理系统计费系统IPATM软交换SS7MGMGIPATMH.248/MGCPH.248/MGCP软交换模型TDMTDM分组网扩展业务管理系统计费系统核心变化将传统交换机的功能模块分离成为独立的网络部件，各个部件可以按相应的功能划分各自独立发展。部件间的协议接口基于相应的标准,有利于实现各种异构网的互通。CS：软交换系统与传统设备区别电路交换模型呼叫控制83CS：传统PSTN网络存在问题传统网络的仅支持单业务(语音)交换能力成为发展的最大瓶颈,低层交换能力支持并约束了高层能力;传统网络业务控制对象和业务应用单元被封闭在业务交换网内,同时用户接口和网络接口的不同使用户的业务能力受限;CS：传统PSTN网络存在问题传统网络的仅支持单业务(语音)84CS:Softswitch:PSTN-IPArchSS7SignallingGatewayPSTNTrunksMediaGateway(Trunking)PSTNOriginatingorTandemSwitch(es)SS7NetworkMediaGatewayControllerMediaGateway(Trunking)RTP/UDP/IPStream{Megaco}SS7SignallingGateway{Megaco}MediaGatewayControllerPSTNTrunksVoIPTerminalsPSTNOriginatingorTandemSwitch(es)SS7Network{M3UA/SCTP}{SS7}{SS7}{TDM}{TDM}{M3UA/SCTP}{SIP-T}CS:Softswitch:PSTN-IPArch85CS：软交换结构–网元组成MediaGatewayController（MGC）：Softswitch:SignalingGateway【信令网关】MediaGateway【媒体网关】TrunkinggatewayLineGatewayResidentialGateway软交换的新业务成本仅为PSTN的【五分之一】。开发周期为PSTN的【十分之一】。占地是传统电路交换机的十分之一。CS：软交换结构–网元组成MediaGatewayC86CS：MGC–媒体网关控制器的功能ContainsallcallcontrolintelligenceImplementscalllevelfeatures(forward,transfer,conference,hold,…)挂机状态摘机状态通话状态拨号状态忙音状态振铃状态请求呼叫状态回铃状态摘机拨号拨号正确拨号拨号错误被叫振铃被叫摘机被叫用户忙被叫无应答被叫挂机主叫挂机收到新的呼叫摘机

CS：MGC–媒体网关控制器的功能Containsal87Master/slavecontrolofMGsbyMGCs

ConnectioncontrolDevicecontrolandconfiguration软交换机【MGC】控制各种网关协议：

Megaco协议（当前使用）

MGCP协议（过去使用）CS：MGC–媒体网关控制器协议Master/slavecontrolofMGs88Endpoint(eg.H.323Gateway,Terminal,MCU)

GatewayFunction(eg.H.323Gateway,Terminal,MCU)

CallAgentMediaGatewayControllerSignallingGatewayPSTN,ATM,etctrunkslinesSS7etcSigtranAnalogMediaGatewayPSTNtrunkingMediaGatewayPSTNlineMediaGatewayIPPhoneMediaGatewayMegacoScopeCS:软交换系统组成与功能

MegacoProtocolCallcontrol(eg.H.323,SIP…)EndpointGatewayFunctionCallA89H.248IP(orATM)NetworkPBX/COPBX/COMediaGWControllerMediaGatewayDevicecontrolDevicecontrolIPPhoneMediaGatewayTelephone/ResidentialMediaGatewayPSTNtrunkingMediaGatewayPSTNlineMediaGatewayPBXMediaGatewayMediaGateway【媒体网关】:功能与分类ConnectionanddevicecontrolNocallprocessing,nocallmodelService-independentH.248IP(orATM)NetworkPBX/CO90CS:SignalingGateway【信令网关】：功能SignalingGatewaysprovideinteractionbetweentheSS7networkandMediaGatewayControllers.ConvertSS7toIPpacketsConvertIPtoSS7packetsSignalingtransport(SS7,SIP-T,Q.931…)ExtremelysecureExtremelyfaulttolerantCS:SignalingGateway【信令网关】：功能91MediaGWControllerTrunkGatewayMegaco/H.248VirtualSwitchSigtransSIP,H.323MediaGatewaySignallingGatewayPBXD-channelB-channelsPRIVirtualSwitchRTPSigtransSignalingGatewaySignalingGatewaySS7COSigtransSigtransTheInternetSS7NetworkCS:SignalingGateway【信令网关】-2MediaGWTrunkGatewayMegaco/V92Softswitch:MGC之间中继信令SIP–SessionInitialProtocol在Softswitch网络，我们需要一个中继信令取代SS7SIP信令是最佳选择Softswitch:MGC之间中继信令SIP–Se93SS7Architecture【专用网络：无法共享】SS7Architecture【专用网络：无法共享】94SS7：ISUPCallEstablishment/ReleaseSS7：ISUPCallEstablishment/Re95SIPProtocol【基于IP网络文本信令】SIPAudioCodecG.711G.723G.729VideoCodecH.261H.263RTPRTCPLANInterfaceTCPIPUDPSIPProtocol【基于IP网络文本信令】SIPAu96SIPArchitectureAsignalingprotocolThesetup,modification,andtear-downofmultimediasessionsSIP+SDPDescribethesessioncharacteristicstopotentialsessionparticipantsSeparatesignalingandmediastreamsSignalingmaypassviaoneormoreproxyorredirectserversMediastreamtakesamoredirectpath.SIPArchitectureAsignalingp97SIPCallSignalingMedia(UDP)RTPStreamRTCPStreamSIPEndpointSIP+SDP(TCPorUDP)InviteRTPStreamSIPGatewayAssumesEndpoints(Clients)knoweachother’sIPaddressesSignalingPlaneBearerPlane200OKAck180RingingSIPCallSignalingMedia(UDP)R98软交换（Softswitch）

在3G移动网络中的应用案例软交换（Softswitch）

在3G移动网络中的应用案例99R4与R99核心网络的差异MSCSCPHLRMSCRANRANRANTDMMSCServerSCPHLRRANRANRANTDM/ATM/IPMGWMGWMSCServerTUP/ISUP/BICCTUP/ISUPR99R4H.248H.248MAPOverTDMMAPOverTDM/IPCAPOverTDMCAPOverTDM/IPR4与R99核心网络的差异MSCSCPHLRMSCRANRA100R5:GfGiIuGiMrGiMsGiRUuMGWGnGcTEMTUTRANGrSGSNGGSNEIRMGCFR-SGW*)MRFMultimediaIPNetworksPSTN/Legacy/ExternalApplications&Services*)MmMwLegacymobileNetworkMcCxAlternativeAccessNetworkMhCSCFCSCFMgT-SGW*)T-SGW*)HSS*)HSS*)Applications&Services*)MSCserverGMSCserverMcMcDCSCPCAPMGWNbNcIuIuR-SGW*)MhCAPCAPIPMultimediaDomain(multimediabySIP,IETFRFC2543)CSDomain(multimediabyITUH.324M)PSDomainCSCFUMTSRelease5:NetworkReferenceModelR5:GfGiIuGiMrGiMsGiRUuMGWGnGcT101Softswitch:分布式组网、设备独立升级软交换机将传统交换机的功能模块分离成为独立的网络部件，各个部件可以按相应的功能划分，各自独立发展。部件间的协议接口基于相应的标准，有利于实现各种异构网的互通。媒体网关可实现拉远，与软交换机可分开放置，使得它们各自可以独立地进行工程实施、扩容和布局。由于业务升级远多于媒体交换能力升级，而采用软交换后，软交换机的数量远小于媒体网关的数量，这将带来大量软件升级费用的节省。Softswitch:分布式组网、设备独立升级软交换机将102分布式组网、设备独立升级(2)移动软交换分布式组网如图所示。对于MSC来说，将媒体网关分散拉远，可以更加靠近BSC，减少话务迂回，节省传输。对于TMSC、GMSC来说，可将媒体网关分散到不同的本地网，做到话务就近接入，集中控制。BSC本地网2ServerMGW1MGW2MGW4MGW3BSC本地网1分布式组网、设备独立升级(2)移动软交换分布式组网如图所示103现代通信网络

ModernTelecommunicationNetworkLecture3(CS)电路交换与软交换北邮软件学院：陈候武Chenhouwu@电话：现代通信网络

ModernTelecommunicatio104CommunicationNetworks【通信网络的分类】CommunicationNetworkSwitched

CommunicationNetworkVirtualCircuitNetwork:MPLSBroadcast

CommunicationNetwork广播，电视，卫星PacketSwitch(PS)-分组交换DatagramNetwork:Internet:IP因特网Circuit-Switched(CS)-电话CommunicationNetworks【通信网络的分105通信业务网(ServiceNetwork)：分类：通信业务网(ServiceNetwork)：分类：106SwitchedNetwork：【通信交换网络】SwitchedNetwork：【通信交换网络】107NodeSwitching（节点交换）Anode(switch)inacircuitswitchingnetworkincominglinksoutgoinglinksNodeNodeSwitching（节点交换）Anode(108Nodes

【交换节点】Nodesmayconnecttoothernodesonly,ortostationsandothernodesNodetonodelinksusuallymultiplexed【复用】NetworkisusuallypartiallyconnectedSomeredundantconnections【冗余连接

】aredesirableforreliabilityTwodifferentswitchingtechnologiesCircuitswitching【电路交换】Packetswitching【分组交换】Nodes【交换节点】Nodesmayconnect109CS:CircuitSwitch电路交换【Overview】CS:CircuitSwitch110CS:CircuitSwitching【电路交换】Dedicatedcommunicationpathbetweentwostations【专用/独享的通信通道】Threephases【呼叫建立：3个阶段】EstablishTransferDisconnectMusthaveswitchingcapacityandchannelcapacitytoestablishconnectionMusthaveintelligencetoworkoutrouting必须具有智能以对呼叫进行选路CS:CircuitSwitching【电路交换】De111CircuitSwitching-ApplicationsInefficientChannelcapacitydedicatedfordurationofconnectionIfnodata,capacitywastedSetup(connection)takestimeOnceconnected,transferistransparentDevelopedforvoicetraffic(phone:电话网)CircuitSwitching-Applicatio112CS：PSTN–

网络结构PSTN–PublicSwitchedTelephoneNetworkUsesdigitaltrunksbetweenCentralOfficeswitches(CO)UsesanaloglinefromphonestoCODigitalTrunks数字中继AnaloglineCentralOfficeCentralOfficeCS：PSTN–网络结构PSTN–PublicSw113PSTN:PublicCircuitSwitchedNetworkPSTN:PublicCircuitSwitched114CS:Components【网络组成】Subscriber【用户：电话】Devicesattachedtonetwork

Subscriberline【用户连线】LocalLoop【本地环路】Subscriberloop【用户环路】ConnectiontonetworkFewkmuptofewtensofkmExchange/Switch【交换机】SwitchingcentersEndoffice-supportssubscribersTrunks【中继线】BranchesbetweenexchangesMultiplexed【复用】CS:Components【网络组成】Subscribe115LegacyDigitalCircuitSwitchCentralizedIntelligenceProprietaryCodeProprietaryservicedeploymentVeryexpensiveLegacyDigitalCircuitSwitchC116CircuitSwitchElements【电路交换组成】CircuitSwitchElements【电路交换组117CircuitSwitchingConceptsDigitalSwitch【数字交换】ProvidetransparentsignalpathbetweendevicesNetworkInterface【网络接口】ControlUnit【控制单元】EstablishconnectionsGenerallyondemandHandleandacknowledgerequestsDetermineifdestinationisfreeconstructpathMaintainconnectionDisconnectCircuitSwitchingConceptsDigi118NodeswitchingSystem:NodeswitchingSystem:119CS：SPC:电话数字程控交换机–模块CS：SPC:电话数字程控交换机–模块120CS:CirtuitSwitch

【SwitchFabric：交换矩阵】现代通信网络课件121SwitchFabric:MxNSwitchFabric:MxN122SwitchFabric:MathgraphpresentationAinputmaysetuponeconnection(1,3,6,7),multipleconnections(4),ornoconnection(2,5,8).SwitchFabric:Mathgraphpres123SwitchFabric:数学模型Inputset:T={0,1,2,…,M-1}Outputset:R={0,1,2,…,N-1}Definition:t∈Tandr∈Rt，Rt∈R，then:c=|t,Rt|isaconnection.tisstartpointoftheconnection,r∈Rtistheendpoint.ifr∈Rt,Rt