現代通信網絡

ModernTelecommunicationNetworkLecture3(CS)電路交換與軟交換北郵軟件學院：陳候武Chenhouwu@電話：現代通信網絡

ModernTelecommunicatio1CommunicationNetworks【通信網絡的分類】CommunicationNetworkSwitched

CommunicationNetworkVirtualCircuitNetwork:MPLSBroadcast

CommunicationNetwork廣播，電視，衛星PacketSwitch(PS)-分組交換DatagramNetwork:Internet:IP因特網Circuit-Switched(CS)-電話CommunicationNetworks【通信網絡的分2通信業務網(ServiceNetwork)：分類：通信業務網(ServiceNetwork)：分類：3SwitchedNetwork：【通信交換網絡】SwitchedNetwork：【通信交換網絡】4NodeSwitching（節點交換）Anode(switch)inacircuitswitchingnetworkincominglinksoutgoinglinksNodeNodeSwitching（節點交換）Anode(5Nodes

【交換節點】Nodesmayconnecttoothernodesonly,ortostationsandothernodesNodetonodelinksusuallymultiplexed【復用】NetworkisusuallypartiallyconnectedSomeredundantconnections【冗余連接

】aredesirableforreliabilityTwodifferentswitchingtechnologiesCircuitswitching【電路交換】Packetswitching【分組交換】Nodes【交換節點】Nodesmayconnect6CS:CircuitSwitch電路交換【Overview】CS:CircuitSwitch7CS:CircuitSwitching【電路交換】Dedicatedcommunicationpathbetweentwostations【專用/獨享的通信通道】Threephases【呼叫建立：3個階段】EstablishTransferDisconnectMusthaveswitchingcapacityandchannelcapacitytoestablishconnectionMusthaveintelligencetoworkoutrouting必須具有智能以對呼叫進行選路CS:CircuitSwitching【電路交換】De8CircuitSwitching-ApplicationsInefficientChannelcapacitydedicatedfordurationofconnectionIfnodata,capacitywastedSetup(connection)takestimeOnceconnected,transferistransparentDevelopedforvoicetraffic(phone:電話網)CircuitSwitching-Applicatio9CS：PSTN–

網絡結構PSTN–PublicSwitchedTelephoneNetworkUsesdigitaltrunksbetweenCentralOfficeswitches(CO)UsesanaloglinefromphonestoCODigitalTrunks數字中繼AnaloglineCentralOfficeCentralOfficeCS：PSTN–網絡結構PSTN–PublicSw10PSTN:PublicCircuitSwitchedNetworkPSTN:PublicCircuitSwitched11CS:Components【網絡組成】Subscriber【用戶：電話】Devicesattachedtonetwork

Subscriberline【用戶連線】LocalLoop【本地環路】Subscriberloop【用戶環路】ConnectiontonetworkFewkmuptofewtensofkmExchange/Switch【交換機】SwitchingcentersEndoffice-supportssubscribersTrunks【中繼線】BranchesbetweenexchangesMultiplexed【復用】CS:Components【網絡組成】Subscribe12LegacyDigitalCircuitSwitchCentralizedIntelligenceProprietaryCodeProprietaryservicedeploymentVeryexpensiveLegacyDigitalCircuitSwitchC13CircuitSwitchElements【電路交換組成】CircuitSwitchElements【電路交換組14CircuitSwitchingConceptsDigitalSwitch【數字交換】ProvidetransparentsignalpathbetweendevicesNetworkInterface【網絡接口】ControlUnit【控制單元】EstablishconnectionsGenerallyondemandHandleandacknowledgerequestsDetermineifdestinationisfreeconstructpathMaintainconnectionDisconnectCircuitSwitchingConceptsDigi15NodeswitchingSystem:NodeswitchingSystem:16CS：SPC:電話數字程控交換機–模塊CS：SPC:電話數字程控交換機–模塊17CS:CirtuitSwitch

【SwitchFabric：交換矩陣】現代通信網絡課件18SwitchFabric:MxNSwitchFabric:MxN19SwitchFabric:MathgraphpresentationAinputmaysetuponeconnection(1,3,6,7),multipleconnections(4),ornoconnection(2,5,8).SwitchFabric:Mathgraphpres20SwitchFabric:數學模型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:數學模型Inputset:21SwitchFabric:連接函數連接函數:inputlink:x(0<=x<=M-1)Outputlinkf(x)(0<=f(x)<=N-1).

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

TIMESWITCHTIMESWITCHTIMESWITCHTIMESWITCHTIMESWITCHTIMESWITCHSPACESWITCHTime/SpaceDivisionMultiplexi25CS：BlockingorNon-blockingBlocking【阻塞】AnetworkisunabletoconnectstationsbecauseallpathsareinuseAblockingnetworkallowsthis【網絡允許Blocking】UsedonvoicesystemsShortdurationcallsNon-blocking【無阻塞】Permitsallstationstoconnect(inpairs)atonceUsedforsomedataconnectionsCS：BlockingorNon-blockingBlo26SwitchingFabric:Blocking如果：I0正在連續到O0,問：I1可以連接到O0orO1???結果：內部阻塞SwitchingFabric:Blocking如果：27解決方案：MultistageSwitchReducednumberofcross

pointsMorethanonepaththroughnetwork

IncreasedreliabilityMorecomplexcontrolMaybeblocking解決方案：MultistageSwitchReduced28解決方案：兩級交換矩陣解決方案：兩級交換矩陣29解決方案：ThreeStageSwitchxxxx解決方案：ThreeStageSwitchxxxx30CS：TST交換矩陣-實例：TST-TimeswitchandSpaceswitch(1)T接線器:Auserinfo.Occupyatimeslot8bitscode.CS：TST交換矩陣-實例：TST-Timesw31（3）TST接線器－512x512TimeSlots（3）TST接線器－512x512TimeSlo32CS:電路交換【PSTN:TrunkMultiplexing】現代通信網絡課件33CO1–CO2:TruckMultiplexingCO1–CO2:TruckMultiplexing34Mux….….….….….11111222….64kb/svoicechannelt4t3t2t12Mb/soutputsignal同步時分復用：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現代通信網絡課件41StatisticalTDM【統計時分復用】InSynchronousTDMmanyslotsarewastedStatisticalTDMallocatestimeslotsdynamicallybasedondemandMultiplexerscansinputlinesandcollectsdatauntilframefullDatarateonlinelowerthanaggregateratesofinputlinesStatisticalTDM【統計時分復用】InSyn42StatisticalTDMFrameFormatsStatisticalTDMFrameFormats43StatisticalTDMvSynchronousTDM

StatisticsTDMdividesadatalinkintosomelogicsub-channelStatisticalTDMvSynchronous44StatisticalTDMvSynchronousTDM：FormatsStatisticalTDMvSynchronous45StatisticalTDM舉例：HDLCHDLC：HighLevelDataLinkControlSynchronoustransmissionAlltransmissionsinframesSingleframeformatforalldataandcontrolexchangesStatisticalTDM舉例：HDLCHDLC：H46HDLC：FrameStructureFlagAddressControlInformationFCSFlag8bits8extendable8/16variable816/32trailerFrameCheckSumHDLC：FrameStructureFlagAddre47HDLC：AddressFieldIdentifiessecondarystationthatsentorwillreceiveframeUsually8bitslongMaybeextendedtomultiplesof7bitsLSBofeachoctetindicatesthatitisthelastoctet(1)ornot(0)Allones(11111111)isbroadcastHDLC：AddressFieldIdentifiess48CS:電路交換【PSTN:Signaling信令】與【CallControl：呼叫控制】CS:電路交換49CS:PSTN控制信令與呼叫控制–各階段Eachconversationrequiresachannelswitchedthroughoutthenetwork呼叫請求：Callrequest；呼叫建立：Callestablished;呼叫接收1.Callisrequested3.Channelisestablished2.CallisacceptedCS:PSTN控制信令與呼叫控制–各階段Each50PSTNCS:PSTN–

電話號碼編碼方案3digitsareacode【區域碼】+3digitsofficecode【局碼】+4digitsphone【本局隨機碼】EachLocalExchangeCarrierswitch(LEC：本地交換局)areassignedablockofatleast10,000numbersTheInter-ExchangeCarrier(IXC：匯接局)switchesareresponsiblefortransmittinglongdistanceIXC212LEC5554210(212)5554210PSTNCS:PSTN–電話號碼編碼方案3digit51CS:PSTN–CallRouting-1InternationalNumberingPlan–E.164【國際電話號碼方案】useprefix-baseddialing4085644555212PSTN1+212+555+5644SS7CS:PSTN–CallRouting-1Int52CS:PSTN–CallRouting-2ThefirstLEC【本地交換機】receivesacall,seeing‘1’asthefirstdigitandthenpassesthecallontotheIXCswitch.TheIXCthenroutesthecall,viaSS7,totheremoteIXCresponsiblefor‘212’.【遠端的212中繼局】The‘212’IXClooksattheofficecodeandpassesitontothe‘555’LECswitch.【515本地局】The‘555’LECswitchthenchecksthestationcodeandsignalstheappropriatephoneCS:PSTN–CallRouting-2The53Signaling:ControlFunctions【控制功能】AudiblecommunicationwithsubscriberTransmissionofdialednumberCallcannotbecompletedindicationCallendedindicationSignaltoringphoneBillinginfoEquipmentandtrunkstatusinfoDiagnosticinfoControlofspecialistequipmentSignaling:ControlFunctions【54PSTN：用戶信令Usesloop-startsignaling【環路信令】Indicatesifthephoneison-hookoroff-hook,orgeneratesring-toneonphone.Closescircuitwhenphoneisoff-hookUsestwowires,tipandringTipFXSRingPSTN：用戶信令Usesloop-startsigna55SwitchtoSwitchSignaling：【中繼信令】SubscribersconnectedtodifferentswitchesOriginatingswitchseizesinterswitchtrunkSendoffhooksignalontrunk,requestingdigitregisterattargetswitch(foraddress)Terminatingswitchsendsoffhookfollowedbyonhook(wink)toshowregisterreadyOriginatingswitchsendsaddressSwitchtoSwitchSignaling：【中繼56中繼信令：基本呼叫流程：中繼信令：基本呼叫流程：57中繼信令：呼叫控制：FSM–FiniteStateMachine

(有限狀態機–

主叫方

)掛機狀態摘機狀態通話狀態撥號狀態忙音狀態振鈴狀態請求呼叫狀態回鈴狀態摘機撥號撥號正確撥號撥號錯誤被叫振鈴被叫摘機被叫用戶忙被叫無應答被叫掛機主叫掛機收到新的呼叫摘機中繼信令：呼叫控制：FSM–FiniteStateM58PSTN:SignalingMethods【中繼信令分類】CAS–ChannelAssociatedSignaling【隨路信令】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【中繼信令分類59Drawbacks【缺點】ofInCASLimitedtransferrateDelaybetweenenteringaddress(dialing)andconnectionOvercomebyuseofcommonchannelsignalingDrawbacks【缺點】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：網元功能SSP(ServiceSwitchingPoint)

SSPsareswitchesthatoriginate,terminate,ortandemcalls.AnSSPsendssignalingmessagestootherSSPstosetup,manage,andreleasevoicecircuitsrequiredtocompleteacall.AnSSPmayalsosendaquerymessagetoaSCPtodeterminehowtorouteacall.【智能網功能】ThefunctionalityoftheSSPisusuallyintegratedintotheCO(CentralOfficeswitch：終端局).STP(SignalTransferPoint)【信號轉接點】NetworktrafficbetweensignalingpointsmayberoutedviaapacketswitchcalledanSTP.AnSTProuteseachincomingmessagetoanoutgoingsignalinglinkbasedonroutinginformationcontainedintheSS7message.AnSTPcanalsoactasa"firewall"toscreenSS7messagesexchangedwithothernetworks.SCP(ServiceControlPoint)【信號控制點】AnSCPisacentralizeddatabasethattellsanSSPhowtorouteacall(e.g.,atoll-free1-800/888call).ItsendsaresponsetotheoriginatingSSPcontainingtheroutingnumber(s)associatedwiththedialednumber.SS7：網元功能SSP(ServiceSwitching65SS7：信令功能SS7在移動網絡中漫游功能的應用SS7：信令功能SS7在移動網絡中漫游功能的應用66CS:電路交換【PSTN:電話網組網原理】現代通信網絡課件67CS：AT&TTelephonyHierarchyClass5Class4Class3Class2Class1CS：AT&TTelephonyHierarchyCla68CS：TelephoneNetworkModelCS：TelephoneNetworkModel69CS：傳統電話網分層結構的問題：層次太多匯接層次（轉接交換機）過多導致呼叫建立延遲傳輸損失。降低了呼叫接通率降低了系統的可靠性一個轉接交換機出問題，將阻塞整個網絡網絡管理復雜CS：傳統電話網分層結構的問題：層次太多70我國電話網：Twolevelsoftransitnetwork

長途網絡結構正在從4層演進到2層（扁平化）DC1(directconnection1)–高層（省間層）DC2(directconnection2)–低層（省內層）我國電話網：Twolevelsoftransitne71CS：局間中繼聯系方式DC1–省際：互聯至其他省；省內：星型連接至DC2DC2–同層DC2之間互聯，或者部分互聯，也可直連至其他省CS：局間中繼聯系方式DC1–省際：互聯至其他省；省內：72CS：本地網互聯方式Alllocalswitchesareconnectedeachotherbydirecttrucks.Suitabletolesslocalswitchesinthesamearea.CS：本地網互聯方式Alllocalswitchesa73CS:電話網的路由選擇高效直達路由(H):永遠是首選低呼損直達路由(L):最后選擇用戶A–呼叫–用戶B：A1-B1,A1-B2-B1,A1-A2-B2-B1,A1-A2-B3-B2-B1,A1-A2-A3-B3-B2-B1CS:電話網的路由選擇高效直達路由(H):永遠是首選74CS：Routing【電路交換：路由定義】ManyconnectionswillneedpathsthroughmorethanoneswitchNeedtofindarouteEfficiencyResilience【彈性】PublictelephoneswitchesareatreestructureStaticroutingusesthesameapproachallthetime【靜態路由】Dynamicroutingallowsforchangesinroutingdependingontraffic【動態路由】UsesapeerstructurefornodesCS：Routing【電路交換：路由定義】Manyco75CS：AlternateRouting【迂回路由】PossibleroutesbetweenendofficespredefinedOriginatingswitchselectsappropriaterouteRouteslistedinpreferenceorderDifferentsetsofroutesmaybeusedatdifferenttimesCS：AlternateRouting【迂回路由】Pos76CS：Alternate

Routing

DiagramCS：AlternateRoutingDiagram77CS:電路交換【SoftSwitch:軟交換】現代通信網絡課件78CS存在問題：解決方案SoftswitchCS存在問題：解決方案Softswitch79Soft-switch：優點Generalpurpose:computerrunningsoftwaretomakeitasmartphoneswitchLowercostsGreaterfunctionalityPacketizingofdigitizedvoicedataAllowingvoiceoverIPMostcomplexpartoftelephonenetworkswitchis【softwarecontrollingcallprocess】CallroutingCallprocessinglogicTypicallyrunningonproprietaryprocessorSeparatecallprocessingfromhardwarefunctionofswitchPhysicalswitchingdonebymediagatewayCallprocessingdonebymediagatewaycontroller【softswitch】Soft-switch：優點Generalpurpose80TraditionalCircuitSwitchingTraditionalCircuitSwitching81CS：Softswitch

【軟交換結構】MediaGatewayController【媒體網關控制器】=Softswitch：軟交換CS：Softswitch【軟交換結構】MediaGat82CS：軟交換系統與傳統設備區別

電路交換模型呼叫控制SS7

LineCardTrunkCardTimeSlot交換TDMTDM管理系統計費系統IPATM軟交換SS7MGMGIPATMH.248/MGCPH.248/MGCP軟交換模型TDMTDM分組網擴展業務管理系統計費系統核心變化將傳統交換機的功能模塊分離成為獨立的網絡部件，各個部件可以按相應的功能劃分各自獨立發展。部件間的協議接口基于相應的標準,有利于實現各種異構網的互通。CS：軟交換系統與傳統設備區別電路交換模型呼叫控制83CS：傳統PSTN網絡存在問題傳統網絡的僅支持單業務(語音)交換能力成為發展的最大瓶頸,低層交換能力支持并約束了高層能力;傳統網絡業務控制對象和業務應用單元被封閉在業務交換網內,同時用戶接口和網絡接口的不同使用戶的業務能力受限;CS：傳統PSTN網絡存在問題傳統網絡的僅支持單業務(語音)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：軟交換結構–網元組成MediaGatewayController（MGC）：Softswitch:SignalingGateway【信令網關】MediaGateway【媒體網關】TrunkinggatewayLineGatewayResidentialGateway軟交換的新業務成本僅為PSTN的【五分之一】。開發周期為PSTN的【十分之一】。占地是傳統電路交換機的十分之一。CS：軟交換結構–網元組成MediaGatewayC86CS：MGC–媒體網關控制器的功能ContainsallcallcontrolintelligenceImplementscalllevelfeatures(forward,transfer,conference,hold,…)掛機狀態摘機狀態通話狀態撥號狀態忙音狀態振鈴狀態請求呼叫狀態回鈴狀態摘機撥號撥號正確撥號撥號錯誤被叫振鈴被叫摘機被叫用戶忙被叫無應答被叫掛機主叫掛機收到新的呼叫摘機

CS：MGC–媒體網關控制器的功能Containsal87Master/slavecontrolofMGsbyMGCs

ConnectioncontrolDevicecontrolandconfiguration軟交換機【MGC】控制各種網關協議：

Megaco協議（當前使用）

MGCP協議（過去使用）CS：MGC–媒體網關控制器協議Master/slavecontrolofMGs88Endpoint(eg.H.323Gateway,Terminal,MCU)

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

CallAgentMediaGatewayControllerSignallingGatewayPSTN,ATM,etctrunkslinesSS7etcSigtranAnalogMediaGatewayPSTNtrunkingMediaGatewayPSTNlineMediaGatewayIPPhoneMediaGatewayMegacoScopeCS:軟交換系統組成與功能

MegacoProtocolCallcontrol(eg.H.323,SIP…)EndpointGatewayFunctionCallA89H.248IP(orATM)NetworkPBX/COPBX/COMediaGWControllerMediaGatewayDevicecontrolDevicecontrolIPPhoneMediaGatewayTelephone/ResidentialMediaGatewayPSTNtrunkingMediaGatewayPSTNlineMediaGatewayPBXMediaGatewayMediaGateway【媒體網關】:功能與分類ConnectionanddevicecontrolNocallprocessing,nocallmodelService-independentH.248IP(orATM)NetworkPBX/CO90CS:SignalingGateway【信令網關】：功能SignalingGatewaysprovideinteractionbetweentheSS7networkandMediaGatewayControllers.ConvertSS7toIPpacketsConvertIPtoSS7packetsSignalingtransport(SS7,SIP-T,Q.931…)ExtremelysecureExtremelyfaulttolerantCS:SignalingGateway【信令網關】：功能91MediaGWControllerTrunkGatewayMegaco/H.248VirtualSwitchSigtransSIP,H.323MediaGatewaySignallingGatewayPBXD-channelB-channelsPRIVirtualSwitchRTPSigtransSignalingGatewaySignalingGatewaySS7COSigtransSigtransTheInternetSS7NetworkCS:SignalingGateway【信令網關】-2MediaGWTrunkGatewayMegaco/V92Softswitch:MGC之間中繼信令SIP–SessionInitialProtocol在Softswitch網絡，我們需要一個中繼信令取代SS7SIP信令是最佳選擇Softswitch:MGC之間中繼信令SIP–Se93SS7Architecture【專用網絡：無法共享】SS7Architecture【專用網絡：無法共享】94SS7：ISUPCallEstablishment/ReleaseSS7：ISUPCallEstablishment/Re95SIPProtocol【基于IP網絡文本信令】SIPAudioCodecG.711G.723G.729VideoCodecH.261H.263RTPRTCPLANInterfaceTCPIPUDPSIPProtocol【基于IP網絡文本信令】SIPAu96SIPArchitectureAsignalingprotocolThesetup,modification,andtear-downofmultimediasessionsSIP+SDPDescribethesessioncharacteristicstopotentialsessionparticipantsSeparatesignalingandmediastreamsSignalingmaypassviaoneormoreproxyorredirectserversMediastreamtakesamoredirectpath.SIPArchitectureAsignalingp97SIPCallSignalingMedia(UDP)RTPStreamRTCPStreamSIPEndpointSIP+SDP(TCPorUDP)InviteRTPStreamSIPGatewayAssumesEndpoints(Clients)knoweachother’sIPaddressesSignalingPlaneBearerPlane200OKAck180RingingSIPCallSignalingMedia(UDP)R98軟交換（Softswitch）

在3G移動網絡中的應用案例軟交換（Softswitch）

在3G移動網絡中的應用案例99R4與R99核心網絡的差異MSCSCPHLRMSCRANRANRANTDMMSCServerSCPHLRRANRANRANTDM/ATM/IPMGWMGWMSCServerTUP/ISUP/BICCTUP/ISUPR99R4H.248H.248MAPOverTDMMAPOverTDM/IPCAPOverTDMCAPOverTDM/IPR4與R99核心網絡的差異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:分布式組網、設備獨立升級軟交換機將傳統交換機的功能模塊分離成為獨立的網絡部件，各個部件可以按相應的功能劃分，各自獨立發展。部件間的協議接口基于相應的標準，有利于實現各種異構網的互通。媒體網關可實現拉遠，與軟交換機可分開放置，使得它們各自可以獨立地進行工程實施、擴容和布局。由于業務升級遠多于媒體交換能力升級，而采用軟交換后，軟交換機的數量遠小于媒體網關的數量，這將帶來大量軟件升級費用的節省。Softswitch:分布式組網、設備獨立升級軟交換機將102分布式組網、設備獨立升級(2)移動軟交換分布式組網如圖所示。對于MSC來說，將媒體網關分散拉遠，可以更加靠近BSC，減少話務迂回，節省傳輸。對于TMSC、GMSC來說，可將媒體網關分散到不同的本地網，做到話務就近接入，集中控制。BSC本地網2ServerMGW1MGW2MGW4MGW3BSC本地網1分布式組網、設備獨立升級(2)移動軟交換分布式組網如圖所示103現代通信網絡

ModernTelecommunicationNetworkLecture3(CS)電路交換與軟交換北郵軟件學院：陳候武Chenhouwu@電話：現代通信網絡

ModernTelecommunicatio104CommunicationNetworks【通信網絡的分類】CommunicationNetworkSwitched

CommunicationNetworkVirtualCircuitNetwork:MPLSBroadcast

CommunicationNetwork廣播，電視，衛星PacketSwitch(PS)-分組交換DatagramNetwork:Internet:IP因特網Circuit-Switched(CS)-電話CommunicationNetworks【通信網絡的分105通信業務網(ServiceNetwork)：分類：通信業務網(ServiceNetwork)：分類：106SwitchedNetwork：【通信交換網絡】SwitchedNetwork：【通信交換網絡】107NodeSwitching（節點交換）Anode(switch)inacircuitswitchingnetworkincominglinksoutgoinglinksNodeNodeSwitching（節點交換）Anode(108Nodes

【交換節點】Nodesmayconnecttoothernodesonly,ortostationsandothernodesNodetonodelinksusuallymultiplexed【復用】NetworkisusuallypartiallyconnectedSomeredundantconnections【冗余連接

】aredesirableforreliabilityTwodifferentswitchingtechnologiesCircuitswitching【電路交換】Packetswitching【分組交換】Nodes【交換節點】Nodesmayconnect109CS:CircuitSwitch電路交換【Overview】CS:CircuitSwitch110CS:CircuitSwitching【電路交換】Dedicatedcommunicationpathbetweentwostations【專用/獨享的通信通道】Threephases【呼叫建立：3個階段】EstablishTransferDisconnectMusthaveswitchingcapacityandchannelcapacitytoestablishconnectionMusthaveintelligencetoworkoutrouting必須具有智能以對呼叫進行選路CS:CircuitSwitching【電路交換】De111CircuitSwitching-ApplicationsInefficientChannelcapacitydedicatedfordurationofconnectionIfnodata,capacitywastedSetup(connection)takestimeOnceconnected,transferistransparentDevelopedforvoicetraffic(phone:電話網)CircuitSwitching-Applicatio112CS：PSTN–

網絡結構PSTN–PublicSwitchedTelephoneNetworkUsesdigitaltrunksbetweenCentralOfficeswitches(CO)UsesanaloglinefromphonestoCODigitalTrunks數字中繼AnaloglineCentralOfficeCentralOfficeCS：PSTN–網絡結構PSTN–PublicSw113PSTN:PublicCircuitSwitchedNetworkPSTN:PublicCircuitSwitched114CS:Components【網絡組成】Subscriber【用戶：電話】Devicesattachedtonetwork

Subscriberline【用戶連線】LocalLoop【本地環路】Subscriberloop【用戶環路】ConnectiontonetworkFewkmuptofewtensofkmExchange/Switch【交換機】SwitchingcentersEndoffice-supportssubscribersTrunks【中繼線】BranchesbetweenexchangesMultiplexed【復用】CS:Components【網絡組成】Subscribe115LegacyDigitalCircuitSwitchCentralizedIntelligenceProprietaryCodeProprietaryservicedeploymentVeryexpensiveLegacyDigitalCircuitSwitchC116CircuitSwitchElements【電路交換組成】CircuitSwitchElements【電路交換組117CircuitSwitchingConceptsDigitalSwitch【數字交換】ProvidetransparentsignalpathbetweendevicesNetworkInterface【網絡接口】ControlUnit【控制單元】EstablishconnectionsGenerallyondemandHandleandacknowledgerequestsDetermineifdestinationisfreeconstructpathMaintainconnectionDisconnectCircuitSwitchingConceptsDigi118NodeswitchingSystem:NodeswitchingSystem:119CS：SPC:電話數字程控交換機–模塊CS：SPC:電話數字程控交換機–模塊120CS:CirtuitSwitch

【SwitchFabric：交換矩陣】現代通信網絡課件121SwitchFabric:MxNSwitchFabric:MxN122SwitchFabric:MathgraphpresentationAinputmaysetuponeconnection(1,3,6,7),multipleconnections(4),ornoconnection(2,5,8).SwitchFabric:Mathgraphpres123SwitchFabric:數學模型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