[信息与通信]7号共路信令.ppt
94页
7号共路信令徐名海徐名海d0207@南京邮电大学通信与信息工程学院南京邮电大学通信与信息工程学院 2024/9/112提 纲p 电路交换、报文交换与分组交换电路交换、报文交换与分组交换p SS7SS7的基本概念的基本概念p MTPMTPp TUPTUPp SCCPSCCPp MAPMAP 2024/9/113交换方式(1)：电路交换A B C D t连接建立数据传送报文连接释放w电路交换（CS：Circuit Swtching)Ø过程：n连接建立n信息传送n连接释放Ø特点：n面向连接的物理通道（端到端）n透明传送n无差错控制措施n过负荷时呼损率增加，但不影响已建立的呼叫 2024/9/114交换方式(2)：报文交换w报文交换Ø报文结构 首部中含地址信息Ø存储转发(逐段行为逐段行为)•把收到的分组先放入缓存（暂时存储）；•查找转发表，找出到某个目的地址应从哪个端口转发；•把分组送到适当的端口转发出去Ø时延较大n时延构成：1.传输时延（链路）2.存储时延存储时延（（结点）3.处理与排队时延（结点）报文报文报文A B C Dt数 据首部报文 2024/9/115交换方式(3)：分组交换w分组交换Ø将报文要传送的信息分为若干个分组（packet），每一个分组有一个头部，含有可供选路的信息和其他控制信息。
Ø减少了存储时间数 据数 据数 据报文数 据首部分组 1数 据首部分组 2数 据首部分组 3 2024/9/116交换方式(3)：分组交换w分组交换的优点：Ø动态分配传输带宽，对通信链路是逐段占用 Ø以分组为传送单位和查找路由Ø不必先建立连接就能向其他主机发送分组；充分使用链路的带宽Ø完善的网络协议；自适应的路由选择协议使网络有很好的生存性 A B C DP1P2P3P4P1P2P3P4P3P4P2P1t 2024/9/117交换方式(3)：分组交换w分组交换的问题：Ø分组在各结点存储转发时需要排队，这就会造成一定的时延 Ø分组必须携带的首部（里面有必不可少的控制信息）也造成了一定的开销u分组长度的确定兼顾时延与开销 2024/9/118交换方式 2024/9/119通信服务的类型：面向连接服务通信服务的类型：面向连接服务/无连接无连接服务服务w面向连接服务(Connection-Oriented)n面向连接服务具有连接建立、数据传输和连接释放这三个阶段 w无连接服务(ConnectionLess) n两个实体之间的通信不需要先建立好连接。
n是一种不可靠的服务这种服务常被描述为“尽最大努力交付”(best effort delivery)或“尽力而为” 2024/9/1110分组交换中的两种服务方式分组交换中的两种服务方式w虚电路方式 面向连接服务 逻辑连接 交换虚电路、永久虚电路w数据报方式 无连接服务 每个分组根据目的地址独立选路 2024/9/1111虚电路服务方式 2024/9/1112数据包服务方式 2024/9/1113虚电路服务虚电路服务 VS 数据报服务数据报服务对比的方面对比的方面虚电路服务虚电路服务数据报服务数据报服务思路可靠通信应当由网络来保证可靠通信应当由用户主机来保证连接的建立必须有不要目的站地址仅在连接建立阶段使用，每个分组使用短的虚电路号每个分组都有目的站的全地址分组的转发属于同一条虚电路的分组均按照同一路由进行转发每个分组独立选择路由进行转发当结点出故障时 所有通过出故障的结点的虚电路均不能工作 故障结点可能丢失分组，一些路由可能会发生变化分组的顺序总是按发送顺序到达目的站 到达目的站时不一定按发送顺序端到端的差错处理和流量控制 可以由分组交换网负责也可以由用户主机负责由用户主机负责 2024/9/1114电路交换电路交换VS分组交换分组交换对比的方面对比的方面电路交换电路交换分组交换分组交换服务种类面向连接服务面向连接服务（虚电路）、无连接服务（数据包）带宽分配固定分配带宽，利用率低动态分配带宽，利用率高特点实时交换。
时延小存储转发，非实时交换有比较大的时延迟适合业务业务突发业务、数据业务 SS7SS7的基本概念的基本概念n SS6，SS7n CAS，CCSn SS7 Structuren Identification of Signaling Points and Trunksn SS7 Signal Units and Primitivesn Acronyms2024/9/1115 SS6，SS7w mid-1970s -CCITT No.6, international network -Bell System, Common-channel interoffice signaling (CCIS) w SS6: FDM (analog)/PCM (digital)w second generation: SS7, CCITT Yellow Books (1981)w application expanded: call control, ISDN w several national versions defined -ANSI/BELLCORE, U.S. networks - British Telecom’s National User Part, U.K. network2024/9/1116 CAS，CCSw In channel-associated signaling (CAS) systems, the signaling information for a trunk is carried by the trunk itself. w In common-channel signaling (CCS), a common signaling link (SL) carries signaling messages for a number of trunks.w CCS: much faster, more flexible, Subscribers cannot access the CCS signaling links.2024/9/1117 SS7 Structure2024/9/1118 2024/9/1119 Transfer of a TUP message(1)TUP message, (2)MTP3 message, (3)MSU2024/9/1120 Identification of Signaling Points Identification of Trunks2024/9/1122 2024/9/1123 2024/9/1124 2024/9/1125 2024/9/1126 Structure of MTP22024/9/1127 2024/9/1128 2024/9/1129 MTP3 Message Format2024/9/1130 2024/9/1131 MTP3 Signal Network Management 2024/9/1132 TUPn General Message Structuren Call-Control Messages and Signalsn Basic Signaling Sequences2024/9/1133 2024/9/1134 2024/9/1135 2024/9/1136 2024/9/1137 2024/9/1138 2024/9/1139 2024/9/1140 2024/9/1141 2024/9/1142 2024/9/1143RLG-Release Guard:正常呼叫结束时的电路释放监正常呼叫结束时的电路释放监护消息，前方局只有收到后向局发来的护消息，前方局只有收到后向局发来的RLG，才能，才能将此电路释放给新的呼叫使用。
将此电路释放给新的呼叫使用 SCCP-Signaling Connection Control Partn SCCP提出背景n SCCP结构与接口n SCCP消息与参数n SCCP Routing Control (SCRC)2024/9/1144 SCCP提出背景w 4级结构采用逐段转发的方式传送SS7，增大中间点的无效负荷，增加消息传送时延w 根据DPC选路，必须知道每个目的的信令点编码，PC不具有全局意义w SI识别消息用户，4bit，不适应业务增长需要w MTP指支持数据报传送方式，某些应用须采用虚电路方式w CCITT提出1984年SCCP分层，1988、1992完善增强 2024/9/1145 2024/9/1146 The SCCP Message Structure2024/9/1147 2024/9/1148 2024/9/1149 2024/9/1150 2024/9/1151 2024/9/1152 Introduction to GSM-MAPp GSM Radio Channelsp Signaling Interfaces and Protocolsp Signaling between mobile and networkp Layer 3 Messages on the Um Interfacep Operations related to location updatingp Operations for calls terminating at MSp Operations and Procedures for originating calls 2024/9/1154 2024/9/1155 Signaling Interfaces and Protocolsn Um and A interfacen Equipment entities and interfacesn Identification of GSM entitiesn Info. in SIM,HLR,VLR,EIR, and AUC Um and A Interfaces Um Interface (1/2) Physical Layer: this consists of those parts of the RF channels that contain signaling channels (SACCH, FACCH, BCCH, SCH, FCCH, PAGCH, RACH, and SDCCH). Data Link Layer: the protocol is known as LAPDm, and is a modified version of the link access protocol for D-channels of DSS1. Messages Layer: RR(无线资源管理), MM（移动管理）, CM（连接管理） Um Interface (2/2) A Interface Physical Layer: 64kb/s channels Data Link Layer: MTP2 Message Layer: BSSAP (base station subsystem application part) DTAP BSSMAP Transfer of RR messages Transfer of MM and CM messages Equipment entities and interfaces(1/2) Equipment entities and interfaces(2/2) Identification of GSM entities LAI: Location Area Identity MCC-MNC-LAC IMSI: International Mobile Station Identity MCC-MNC-MSIN (Mobile Station Identity Number) TMSI: Temporary Mobile Station Identity (32bit) IMEI: International Mobile Equipment Identity (15-digit) MSRN: Mobile Station Roaming Number used by the fixed network to extend the call set-up to the MSC Info. In SIM Info. In HLR Info. In VLR Info. In AUC Signaling between mobile and networkn MS Initializationn Idle MSn Location Updatingn Set-up of a call Originated by MSn Connection Set-up for Call Terminating at MSn Release of Connection MS Initialization Idle MS w Location Updating wCall Originated by MS wCall Terminating at MS wCall Clearing Layer 3 Messages on the Um Interfacen Messages for RRn Messages for MMn Messages for CC Messages for RR Assignment Command: network->MS, TACH Assignment Complete: MS->network, Resp. Channel Release: network->MS, release cause IE Channel Request: MS->network, SDCCH Cipher Mode Command: sent by the network on SDCCH Cipher Mode Complete: sent by MS on SDCCH Immediate Assignment: sent by the network on PAGCH, resp. to channel req. Paging Request: sent by the network on PAGCH, informing an incoming call Paging Response: sent by the MS on SDCCH to confirm the receipt of a paging request System Information Messages: BCCH Messages for MM Authentication Request: sent by the network on SDCCH. RAND Authentication Response: resp., SRES CM Service Request: sent by MS on SDCCH IMSI Detach Indication: sent by MS on SDCCH, before power-down Location Updating Accept: sent by the network on SDCCH Location Updating Request: sent by MS on SDCCH TMSI Reallocation Command: sent by the network TMSI Reallocation Complete: sent by MS Messages for CC Alerting: MS-O, network; MS-T, MS Call Confirmed: sent by a called MS Call Proceeding: MS-O, by the network Connect: MS-O, network; MS-T, MS answered Connect Acknowledge: receipt of a connect message Disconnect: request the release of the connection Release: ack. a received disconnect message or indicate a network-initiated release Release Complete: ack. A release message Set-up: MS or the network, including: bearer capability, called party address, calling party address, etc. Operations related to location updatingn Operations for LU. Mobile is known at VLRn Initial operations for LU. Mobile is not known at VLR, and is identified by LAIs and TMSIsn Initial operations for LU. Mobile is not known at VLR, and is identified by IMSIn Subsequent operations for LUn Final operations for LU Operations for LU. Mobile is known at VLR Initial operations for LU. Mobile is not known at VLR, and is identified by LAIs and TMSIs Initial operations for LU. Mobile is not known at VLR, and is identified by IMSI Subsequent operations for LU w Final operations for LU Operations for calls terminating at MSn Routing calls to the visited MSCn Operations for terminating callsn Terminating call procedures Routing calls to the visited MSC (1/3) Routing calls to the visited MSC (2/3) Routing calls to the visited MSC (3/3) Operations for terminating calls MAP_SEND_ROUTING_INFORMATION MAP_PROVIDE_ROAMING_NUMBER MAP_SEND_INFO_FOR_INCOMING_CALL MAP_PAGE MAP_PROCESS_ACCESS_REQUEST MAP_COMPLETE_CALL Obtaining MSRN Operations for terminating calls Operations for originating calls 。
