Mạng và viễn thông P12

Signalling System Noe 7TheITU-Tsignallingsystemnumber7, SS number7,SS7,CCITT7,C7 or numberseven signalling system is the most recently developed of telephone network signalling systems. It is already widely deployed in digital telephone networks and ISDNs across the world, and also will be a ‘cornerstone’ of ‘intelligent networks’ and broadband ISDNs (B-ISDN).
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Mạng và viễn thông P12 Networks and Telecommunications: Design and Operation, Second Edition. Martin P. Clark Copyright © 1991, 1997 John Wiley & Sons Ltd ISBNs: 0-471-97346-7 (Hardback); 0-470-84158-3 (Electronic) 12 Signalling System Noe 7 TheITU-Tsignallingsystemnumber7, SS number7,SS7,CCITT7,C7 or numberseven signalling system is the most recently developed of telephone network signalling systems. It is already widely deployed in digital telephone networks and ISDNs across the world, and also will be a ‘cornerstone’ of ‘intelligent networks’ and broadband ISDNs (B-ISDN). It is a complex, commonchannelsignallingsystem,whichenablesthecontrollingprocessors of twodigital exchanges or databases to communicatedirectlyandinteractwithoneanotherinamanner optimized for digital transmission media.SS7 has also formed the basis of a number of further- developedregionalsignallingsystems. In theUnitedStates,forexample,‘ANSISS7’isa derivative, while the UK national version is ‘C7/BT’. This chapter describes the overall structure and capabilities of SS7.12.1 SS7 SIGNALLING BETWEEN EXCHANGES The SS7 signalling system is described in the 4.700 series of ITU-T recommendations. A common channel signalling system, optimized for digital networks, it allows direct transferofcallinformationtransfer between exchangeprocessors. Comprising a number of layered and modular parts, each with a different function, it is a powerful general-purpose signalling system capable of supporting a range of applications and administrative functions, including e ISDN (integrated services digital network) e intelligentnetworks ( I N S ) e mobileservices (e.g. cellular radio) e networkadministration,operationandmanagement 249250 SIGNALLING SYSTEM NO. 7 In addition, its modular naturelends itself to the development of new user parts which may be designed to support almost any new service that can be conceived. The user parts of the system that have been developed so far are 0 MTP message transfer part 0 SCCP signalling connection and control part 0 TUP telephone user part 0 DUP data user part 0 ISUP ISDN services user part 0 TC transaction capabilities (used by intelligent networks) 0 TCAP transaction capabilities application part 0 OMAP operation and maintenance application part 0 INAP intelligent network application part 0 MAP mobile application part The MTP and SCCP form the ‘foundations’ of the system, providing for carriage of messages. The TUP, DUP and ISUP use the MTP and/or SCCP to convey messages relating to call control,for telephone, data, and ISDN networks, respectively. The OMAP, MAP and INAP are other application parts for operation and maintenance interaction, mobile network control and intelligent network services, respectively. Initially the SS7 system was designed so that the MTP could be used in association with any or all of the telephone, data and ISDN user parts. However, following the emergence of the OS1 model, the SCCP was developed as an adjunct to the MTP; the two in combination provide the functions of the OS1 network service (layers 1-3). SS7 signalling can be installed between two exchanges, provided that the necessary signallingfunctions are availablein both exchanges.Thefunctionsresideinaunit termed a signalling point. This may be a separate piece of hardware to the exchange, but usually it is a software function in the exchange central processor.SS7 signalling points (SPs),basically exchanges, intercommunicate via signalling links and are said to share a signalling relation. A single SS7 signalling link enables information to be passed directly between two exchange processors, allowing the set-up, control, and release of not ju ...