现代通信网络课件

Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,现代通信网络,Modern Telecommunication Network,Lecture 3,(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Modern Telecommunicatio,1,Communication Networks【,通信网络的分类,】,Communication Network,SwitchedCommunication Network,Virtual Circuit Network:MPLS,BroadcastCommunication,Network,广播，电视，卫星,Packet Switch,(PS),-,分组交换,Datagram Network:,Internet:IP,因特网,Circuit-Switched,(CS)-,电话,Communication Networks【通信网络的分,2,通信业务网,(Service Network),：分类：,通信业务网(Service Network)：分类：,3,Switched Network,：【,通信交换网络,】,Switched Network：【通信交换网络】,4,Node Switching（,节点交换）,A node(switch)in a circuit switching network,incoming links,outgoing links,Node,Node Switching（节点交换）A node(,5,Nodes,【,交换节点,】,Nodes may connect to other nodes only,or to stations and other nodes,Node to node links usually multiplexed,【,复用,】,Network is usually partially connected,Some redundant connections,【,冗余连接,】,are desirable for reliability,Two different switching technologies,Circuit switching,【,电路交换,】,Packet switching,【,分组交换,】,Nodes【交换节点】Nodes may connect,6,CS:Circuit Switch,电路交换,【Overview】,CS:Circuit Switch,7,CS:Circuit,Switching,【,电路交换,】,Dedicated communication path between two stations,【,专用,/,独享的通信通道,】,Three phases,【,呼叫建立：,3,个阶段,】,Establish,Transfer,Disconnect,Must have switching capacity and channel capacity to establish connection,Must have intelligence to work out routing,必须,具有智能以对呼叫进行选路,CS:Circuit Switching【电路交换】De,8,Circuit Switching-Applications,Inefficient,Channel capacity dedicated for duration of connection,If no data,capacity wasted,Set up(connection)takes time,Once connected,transfer is transparent,Developed for voice traffic(,phone,:,电话网,),Circuit Switching-Applicatio,9,CS,：,PSTN,网络结构,PSTN,Public Switched Telephone Network,Uses digital trunks between Central Office switches(CO),Uses analog line from phones to CO,Digital Trunks,数字中继,Analog line,Central,Office,Central,Office,CS：PSTN 网络结构PSTN Public Sw,10,PSTN:,Public Circuit Switched Network,PSTN:Public Circuit Switched,11,CS:,Components,【,网络组成,】,Subscriber,【,用户：电话,】,Devices attached to network,Subscriber line【,用户连线,】,Local Loop,【,本地环路,】,Subscriber loop,【,用户环路,】,Connection to network,Few km up to few tens of km,Exchange,/Switch【,交换机,】,Switching centers,End office-supports subscribers,Trunks,【,中继线,】,Branches between exchanges,Multiplexed,【,复用,】,CS:Components【网络组成】Subscribe,12,Legacy Digital Circuit Switch,Centralized Intelligence,Proprietary Code,Proprietary service deployment,Very expensive,Legacy Digital Circuit SwitchC,13,Circuit Switch Elements,【,电路交换组成,】,Circuit Switch Elements【电路交换组,14,Circuit Switching Concepts,Digital Switch,【,数字交换,】,Provide transparent signal path between devices,Network Interface,【,网络接口,】,Control Unit,【,控制单元,】,Establish connections,Generally on demand,Handle and acknowledge requests,Determine if destination is free,construct path,Maintain connection,Disconnect,Circuit Switching ConceptsDigi,15,Node switching System:,Node switching System:,16,CS,：,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,17,CS:Cirtuit Switch,【Switch Fabric,：交换矩阵,】,现代通信网络课件,18,Switch Fabric:M x N,Switch Fabric:M x N,19,Switch Fabric:Math graph presentation,A input may setup one connection(1,3,6,7),multiple connections(4),or no connection(2,5,8).,Switch Fabric:Math graph pres,20,Switch Fabric:,数学模型,Input set:T=0,1,2,M-1,Output set:R=0,1,2,N-1,Definition:,t T and r Rt,，,Rt R，then:c=|t,Rt|is a connection.,t is start point of the connection,r Rt is the end point.,if r Rt,Rt contains only one item,this connection is point to point.,if r Rt,Rt contains more than one item,this connection is point to multi-point.,Multicast:Rt R;Broadcast:Rt=R,connection set in switch fabric:C=|c0,c1,c2,|,Switch Fabric:数学模型Input set:,21,Switch Fabric:,连接函数,连接函数,:input link:x(0=x=M-1),Output link f(x)(0=f(x)=N-1).,例如：连接函数,:(x2,x1,x0)=x1,x0,x2,(000)=000,(001)=010,(010)=100,(111)=111,Switch Fabric:连接函数连接函数:inpu,22,Switching Fabric:Time Division,Time-slot switching is a device,which buffers,m,incoming time-slots,arranges new transmit order and transmits,n,time-slots,Used in Packet switch and ATM as well as digital telephone switch,Switching Fabric:Time Divisio,23,Switching Fabric:Space Division,Switching Fabric:Space Divisi,24,Time/Space Division Multiplexing,TIME SWITCH,TIME SWITCH,TIME SWITCH,TIME SWITCH,TIME SWITCH,TIME SWITCH,SPACE SWITCH,Time/Space Division Multiplexi,25,CS,：,Blocking,or Non-blocking,Blocking,【,阻塞,】,A network is unable to connect stations because all paths are in use,A blocking network allows this,【,网络允许,Blocking】,Used on voice systems,Short duration calls,Non-blocking,【,无阻塞,】,Permits all stations to connect(in pairs)at once,Used for some data connections,CS：Blocking or Non-blockingBlo,26,Switching Fabric:Blocking,如果：,I0,正在连续到,O0,问：,I1,可以连接到,O0 or O1?,结果：内部阻塞,Switching Fabric:Blocking如果：,27,解决,方案：,Multistage Switch,Reduced number of cross,points,More than one path through network,Increased reliability,More complex control,May be blocking,解决方案：Multistage SwitchReduced,28,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,：,Three Stage Switch,x,x,x,x,解决方案：Three Stage Switchxxxx,30,CS,：,TST,交换矩阵,-,实例：,TST -Time switch and Space switch,(1)T,接线器,:A user info.Occupy a time slot 8 bits code.,CS：TST交换矩阵-实例：TST -Time sw,31,（,3,）,TST,接线器,512 x 512 Time Slots,（3）TST 接线器 512 x 512 Time Slo,32,CS:,电路交换,【PSTN:Trunk Multiplexing】,现代通信网络课件,33,CO1 CO2:Truck Multiplexing,CO1 CO2:Truck Multiplexing,34,Mux,.,.,.,.,.,1,1,1,1,1,2,2,2,.,64kb/s voice channel,t4 t3 t2 t1,2Mb/s output signal,同步时分复用：,Synchronous TDM,Mux.11111222.64kb/s,35,E1:2Mb/s frame structure,All Timeslots contain 8 bit words,(PCM,Data,Subrate,n x 64 kb/s),Network Signaling-CAS or CCS,0,1,2,314,15,16,1730,31,0,1 frame-256 bits-125,m,s,Frame Alignment Word,3.9us,Network Signaling,Channels 1 to 15,Channels 16 to 30,E1:2Mb/s frame structureAll T,36,MUX MUX MUX MUX MUX,1,2,3,4,1,2,3,4,E1,E1,E1,E1,E2,E2,E2,E2,E5,2.048 8.448 34.368 139.264 561.480,Mbps Mbps Mbps Mbps Mbp,s,CH2,CH1,CH32,E3 1,E3 2,E3 3,E3 4,E4 1,E4 2,E4 3,E4 4,ITU-T E1 DIGITAL MULTIPLEXING HIERARCHY,E1 E2 E3 E4 E5,1 E1 E52.048,37,ANSI,：,T1-T-carrier system 1.544M,Each frame carries one sample(8 bits)for each 24 channels,plus one framing bit=193 bits,193*8000(samples/sec)=1.544 Mbit/sec=T-1,Channel 1,Channel 2,Channel 3,Channel 24,Channel,1,Channel,2,Channel,3,Channel,24,Framing Bit,1 D4 Frame,TDM,ANSI：T1-T-carrier system 1.5,38,ANSI:T1/DS1 Frame Structure-,1.544 Mbps,Every 8th bit used for signaling,inefficient,0,1,2,21,22,620,23,1 frame-193 bits-24 channels,Bit 8-reserved for signaling,Framing bit,3,4,5,0,1,Bits 1-7 Payload,ANSI:T1/DS1 Frame Structure,39,ANSI:DIGITAL MULTIPLEXING HIERARCHY,T1 T2 T3 T4 T5,MUX MUX MUX MUX MUX,1,2 T3 1,3 T3 2,4 T3 3,5 T3 4,6 T3 5,7 T3 6,1,2,3,4,1,2,T1,T1,T1,T1,T2,T2,T2,T2,T2,T2,T2,T4,T4,T5,CH1,CH2,CH24,24,VF,1.544 6.312 44.736 274.176 560.160,Mbps Mbps Mbps Mbps Mbps,ANSI:DIGITAL MULTIPLEXING,40,现代通信网络课件,41,Statistical TDM【,统计时分复用,】,In Synchronous TDM many slots are wasted,Statistical TDM allocates time slots dynamically based on demand,Multiplexer scans input lines and collects data until frame full,Data rate on line lower than aggregate rates of input lines,Statistical TDM【统计时分复用】In Syn,42,Statistical TDM Frame Formats,Statistical TDM Frame Formats,43,Statistical TDM v,Synchronous TDM,Statistics TDM divides a data link into some logic sub-channel,Statistical TDM v Synchronous,44,Statistical TDM v Synchronous TDM,：,Formats,Statistical TDM v Synchronous,45,Statistical TDM,举例：,HDLC,HDLC,：,High Level Data Link Control,Synchronous transmission,All transmissions in frames,Single frame format for all data and control exchanges,Statistical TDM 举例：HDLCHDLC：H,46,HDLC,：,Frame Structure,Flag,Address,Control,Information,FCS,Flag,8,bits,8,extendable,8/,16,variable,8,16/,32,trailer,Frame CheckSum,HDLC：Frame Structure FlagAddre,47,HDLC,：,Address Field,Identifies secondary station that sent or will receive frame,Usually 8 bits long,May be extended to multiples of 7 bits,LSB of each octet indicates that it is the last octet(1)or not(0),All ones(11111111)is broadcast,HDLC：Address FieldIdentifies s,48,CS:,电路交换,【PSTN:Signaling,信令,】,与,【Call Control,：呼叫控制,】,CS:电路交换,49,CS:PSTN,控制信令与呼叫控制,各阶段,Each conversation requires a channel switched throughout the network,呼叫请求：,Call request,；呼叫建立：,Call established;,呼叫接收,1.Call is requested,3.Channel is established,2.Call is accepted,CS:PSTN 控制信令与呼叫控制 各阶段Each,50,PSTN,CS:PSTN,电话号码编码方案,3 digits area code【,区域码,】+3 digits office code【,局码,】+4 digits phone【,本局随机码,】,Each Local Exchange Carrier switch(LEC,：本地交换局,)are assigned a block of at least 10,000 numbers,The Inter-Exchange Carrier(IXC,：汇接局,)switches are responsible for transmitting long distance,IXC,212,LEC,555,4210,(212)555 4210,PSTNCS:PSTN 电话号码编码方案3 digit,51,CS:PSTN,Call Routing-1,International Numbering Plan,E.164,【,国际电话号码方案,】,use prefix-based dialing,408,5644,555,212,PSTN,1+212+555+5644,SS7,CS:PSTN Call Routing-1Int,52,CS:PSTN,Call Routing-2,The first LEC,【,本地交换机,】,receives a call,seeing 1 as the first digit and then passes the call on to the IXC switch.,The IXC then routes the call,via SS7,to the remote IXC responsible for 212.【,远端的,212,中继局,】,The 212 IXC looks at the office code and passes it on to the 555 LEC switch.【515,本地局,】,The 555 LEC switch then checks the station code and signals the appropriate phone,CS:PSTN Call Routing-2The,53,Signaling:,Control Functions,【,控制功能,】,Audible communication with subscriber,Transmission of dialed number,Call can not be completed indication,Call ended indication,Signal to ring phone,Billing info,Equipment and trunk status info,Diagnostic info,Control of specialist equipment,Signaling:Control Functions【,54,PSTN,：,用户信令,Uses loop-start signaling【,环路信令,】,Indicates if the phone is on-hook or off-hook,or generates ring-tone on phone.,Closes circuit when phone is off-hook,Uses two wires,tip and ring,Tip,FXS,Ring,PSTN：用户信令Uses loop-start signa,55,Switch to Switch Signaling,：【,中继信令,】,Subscribers connected to different switches,Originating switch seizes interswitch trunk,Send off hook signal on trunk,requesting digit register at target switch(for address),Terminating switch sends off hook followed by on hook(wink)to show register ready,Originating switch sends address,Switch to Switch Signaling：【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,Finite State Machine(,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 Finite State M,58,PSTN:Signaling Methods【,中继信令分类,】,CAS,Channel Associated Signaling【,随路信令,】,Signaling associated with each channel has fixed placement within frame,Traditional T-1 and E-1 for voice uses CAS,CCS,Common Channel Signaling【,共路信令,】,Signaling passed via messaging protocol,out-of-band signaling,Can carry a wide variety of messages,e.g.Caller-ID etc,ISDN uses a CCS-based protocol,Q.931,Q.SIG which is typically used for PBX-to-PBX connectivity,and is a variant of Q.931,is CCD-based,SS7 is the CCS-based protocol used in the PSTN,i.e.between COs,PSTN:Signaling Methods【中继信令分类,59,Drawbacks,【,缺点,】,of In C,AS,Limited transfer rate,Delay between entering address(dialing)and connection,Overcome by use of common channel signaling,Drawbacks【缺点】of In CASLimited,60,CAS v,.,CCS,CAS v.CCS,61,SS7,：,Signaling,System Number 7,SS7,：,Common,channel signaling scheme,ISDN,Optimized for 64k digital channel network,Call control,remote control,management and maintenance,Reliable means of transfer of info in sequence,Will operate over analog and below 64k,Point to point terrestrial and satellite links,SS7：Signaling System Number 7S,62,PSTN,SS7/Signaling System 7,SS7 messages are exchanged between network elements on bi-directional channels(typically T1 lines)called signaling links.,Trunk Lines,SSP,(CO),SSP,(CO),STP,SS7,STP,T-1,T-1,PSTN SS7/Signaling System 7,63,PSTN SS7 Signaling Points,SS7 network is critical to call processing,SCPs and STPs are usually deployed in mated pair configurations in separate physical locations to ensure network-wide service in the event of an isolated failure.,Links between signaling points are also provisioned in pairs.Traffic is shared across all links in the linkset.If one of the links fails,the signaling traffic is rerouted over another link in the linkset.,SS7 Links,STP,STP,SSP,SSP,SCP,SCP,SS7 Links,Trunk Links,PSTN SS7 Signaling Points S,64,SS7,：网元功能,SSP(Service Switching Point),SSPs are switches that originate,terminate,or tandem calls.,An SSP sends signaling messages to other SSPs to setup,manage,and release voice circuits required to complete a call.,An SSP may also send a query message to a SCP to determine how to route a call.【,智能网功能,】,The functionality of the SSP is usually integrated into the CO(Central Office switch,：终端局,).,STP(Signal Transfer Point),【,信号转接点,】,Network traffic between signaling points may be routed via a packet switch called an STP.,An STP routes each incoming message to an outgoing signaling link based on routing information contained in the SS7 message.An STP can also act as a firewall to screen SS7 messages exchanged with other networks.,SCP(Service Control Point),【,信号控制点,】,An SCP is a centralized database that tells an SSP how to route a call(e.g.,a toll-free 1-800/888 call).,It sends a response to the originating SSP containing the routing number(s)associated with the dialed number.,SS7：网元功能SSP(Service Switching,65,SS7,：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,66,CS:,电路交换,【PSTN:,电话网组网原理,】,现代通信网络课件,67,CS,：,AT&T Telephony Hierarchy,Class 5,Class 4,Class 3,Class 2,Class 1,CS：AT&T Telephony HierarchyCla,68,CS,：,Telephone Network Model,CS：Telephone Network Model,69,CS,：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,：,Two levels of transit network,长途网络结构正在从,4,层演进到,2,层（扁平化）,DC1(direct connection 1),高层（省间层）,DC2(direct connection 2),低层（省内层）,我国电话网：Two levels of transit ne,71,CS,：,局间中继联系方式,DC1,省际：互联至其他省；省内：星型连接至,DC2,DC2,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：,72,CS,：,本地网互联方式,All local switches are connected each other by direct trucks.Suitable to less local switches in the same area.,CS：本地网互联方式All local switches a,73,CS:,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-B1,CS:电话网的路由选择高效直达路由(H):永远是首选,74,CS,：,Routing,【,电路交换：路由定义,】,Many connections will need paths through more than one switch,Need to find a route,Efficiency,Resilience【,弹性,】,Public telephone switches are a tree structure,Static routing uses the same approach all the time【,静态路由,】,Dynamic routing allows for changes in routing depending on traffic【,动态路由,】,Uses a peer structure for nodes,CS：Routing 【电路交换：路由定义】Many co,75,CS,：,Alternate Routing【,迂回路由,】,Possible routes between end offices predefined,Originating switch selects appropriate route,Routes listed in preference order,Different sets of routes may be used at different times,CS：Alternate Routing【迂回路由】Pos,76,CS,：,Alternate,Routing,Diagram,CS：Alternate Routing Diagram,77,CS:,电路交换,【SoftSwitch:,软交换,】,现代通信网络课件,78,CS,存在问题：,解决方案,Softswitch,CS 存在问题：解决方案Softswitch,79,Soft-switch,：优点,General purpose:computer running software to make it a smart phone switch,Lower costs,Greater functionality,Packetizing of digitized voice data,Allowing voice over IP,Most complex part of telephone network switch is【software controlling call process】,Call routing,Call processing logic,Typically running on proprietary processor,Separate call processing from hardware function of switch,Physical switching done by media gateway,Call processing done by media gateway controller【softswitch】,Soft-switch：优点General purpose,80,Traditional Circuit Switching,Traditional Circuit Switching,81,CS,：,Softswitch,【,软交换结构,】,Media Gateway Controller【,媒体网关控制器,】=Softswitch,：软交换,CS：Softswitch【软交换结构】Media Gat,82,CS,：软交换系统与传统设备区别,电路交换模型,呼叫控制,SS7,Line Card,Trunk Card,Time Slot,交换,T,D,M,T,D,M,管理系统,计费系统,IP,ATM,软交换,SS7,MG,MG,IP,ATM,H.248/MGCP,H.248/MGCP,软交换模型,T,D,M,T,D,M,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,83,CS,：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),84,CS:Softswitch:PSTN-IP Arch,SS7,Signalling,Gateway,PSTN,Trunks,Media,Gateway,(Trunking),PSTN,Originating or,Tandem,Switch(es),SS7,Network,Media,Gateway,Controller,Media,Gateway,(Trunking),RTP/UDP/IP Stream,Megaco,SS7,Signalling,Gateway,Megaco,Media,Gateway,Controller,PSTN,Trunks,VoIP Terminals,PSTN,Originating or,Tandem,Switch(es),SS7,Network,M3UA/SCTP,SS7,SS7,TDM,TDM,M3UA/SCTP,SIP-T,CS:Softswitch:PSTN-IP Arch,85,CS,：软交换结构,网元组成,Media Gateway Controller,（,MGC,）：,Softswitch:,Signaling Gateway【,信令网关,】,Media Gateway【,媒体网关,】,Trunking gateway,Line Gateway,Residential Gateway,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Media Gateway C,86,CS,：,MGC,媒体网关控制器的功能,Contains all call control intelligence,Implements call level features(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Contains al,87,Master/slave control of MGs by MGCs,Connection control,Device control and configuration,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/slave control of MGs,88,Endpoint,(eg.H.323 Gateway,Terminal,MCU),Gateway Function,(eg.H.323 Gateway,Terminal,MCU),Call Agent,Media Gateway Controller,Signalling Gateway,PSTN,ATM,etc,trunks,lines,SS7 etc,Sigtran,Analog,Media Gateway,PSTN trunking,Media Gateway,PSTN line,Media Gateway,IP Phone,Media Gateway,Megaco Scope,CS:,软交换系统组成与功能,Megaco Protocol,Call control(eg.H.323,SIP),EndpointGateway FunctionCall A,89,H.248,IP(or ATM)Network,PBX/CO,PBX/CO,Media GW Controller,Media Gateway,Device,control,Device,control,IP Phone,Media,Gateway,Telephone/Residential,Media Gateway,PSTN trunking,Media Gateway,PSTN line,Media Gateway,PBX,Media,Gateway,Media Gateway【,媒体网关,】:,功能与分类,Connection and device control,No call processing,no call model,Service-independent,H.248IP(or ATM)NetworkPBX/CO,90,CS:Signaling Gateway,【,信令网关,】,：功能,Signaling Gateways provide interaction between the SS7 network and Media Gateway Controllers.,Convert SS7 to IP packets,Convert IP to SS7 packets,Signaling transport(SS7,SIP-T,Q.931),Extremely secure,Extremely fault tolerant,CS:Signaling Gateway【信令网关】：功能,91,Media GW,Controller,Trunk Gateway,Megaco/,H.248,Virtual Switch,Sigtrans,SIP,H.323,Media Gateway,Signalling Gateway,PBX,D-channel,B-channels,PRI,Virtual Switch,RTP,Sigtrans,Signaling Gateway,Signaling Gateway,SS7,CO,Sigtrans,Sigtrans,TheInternet,SS7Network,CS:Signaling Gateway,【,信令网关,】-2,Media GW Trunk GatewayMegaco/V,92,Softswitch:MGC,之间中继信令,SIP Session Initial Protocol,在,Softswitch,网络，我们需要一个中继信令取代,SS7,SIP,信令是最佳选择,Softswitch:MGC 之间中继信令SIP Se,93,SS7 Architecture【,专用网络：无法共享,】,SS7 Architecture【专用网络：无法共享】,94,SS7,：,ISUP Call Establishment/Release,SS7：ISUP Call Establishment/Re,95,SIP Protocol【,基于,IP,网络文本信令,】,SIP,Audio Codec,G.711,G.723,G.729,Video Codec,H.261,H.263,RTP,RTCP,LAN Interface,TCP,IP,UDP,SIP Protocol【基于IP网络文本信令】SIPAu,96,SIP Architecture,A signaling protocol,The setup,modification,and tear-down of multimedia sessions,SIP+SDP,Describe the session characteristics to potential session participants,Separate signaling and media streams,Signaling may pass via one or more proxy or redirect servers,Media stream takes a more direct path.,SIP Architecture A signaling p,97,SIP Call Signaling,Media(UDP),RTP Stream,RTCP Stream,SIP,Endpoint,SIP+SDP(TCP or UDP),Invite,RTP Stream,SIP,Gateway,Assumes Endpoints(Clients),know each others IP addresses,Signaling Plane,Bearer,Plane,200,OK,Ack,180,Ringing,SIP Call SignalingMedia(UDP)R,98,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