џWPCL ћџ2BJ|xа АH аа АА X агга ХА6p&А6p&Х аеЮ† а Hр аааУ Уб cмˆ4 PŽТ б Fascicle VI.7 Р-Р Rec. Q.700 Ф ФPAGE1б cмˆ4 PŽТ б У УЮееЃ† а HH аааб cмˆ4 PŽТ бPAGE24б cмˆ4 PŽТ бУ У Fascicle VI.7 Р-Р Rec. Q.700 Ѓеа HH ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаа X  аб cмˆ4 PŽТ бAll drawings appearing in this Fascicle have been done in Autocad. ‚У УRecommendation Q.700 аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаСр8<Сб cмˆ4 PŽТ бINTRODUCTION TO CCITT SIGNALLING SYSTEM No. 7 аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ б1ТX ТGeneralФ ФЦЦ а H аС СThis Recommendation provides an overview of the Signalling System by describing the various functional elements of CCITT No. 7 and the relationship between these functional elements. This Recommendation provides a general description of functions and capabilities of the Message Transfer Part (MTP), Signalling Connection Control Part (SCCP), Telephone User Part, ISDN User Part (ISDNР-РUP), Transaction Capabilities (TC), and the Operations, Maintenance and Administration Part (OMAP) which are covered elsewhere in the Q.700 to Q.795 series of Recommendations. However, in the case of contradiction between the specifications and Q.700, the Q.700 to Q.795 specification shall apply. а H аС СSupplementary Services in CCITT S.S. No.7 ISDN applications are described in the Q.73x series of Recommendations. а H аС СIn addition to these functions in the CCITT No. 7 signalling system, the Q.700 to Q.795 series of Recommendations describes the CCITT No. 7 network structure, and also specifies the Tests and Measurements applicable to CCITT No. 7. а H аС СThis Recommendation is also a specification of those aspects such as CCITT S.S. No. 7 Architecture, Flow Control and general compatibility rule which are not specified in separate Recommendations, and are applicable to the overall scope of S.S. No. 7. С СThe remainder of this Recommendation describes: Та ТР-РТ№ ТРSР 2: Signalling network concepts components and modes;ЦЦ а H аТа ТР-РТ№ ТРSР 3: The functional blocks within CCITT Signalling System No. 7 and the services provided by them;ЦЦ Та ТР-РТ№ ТРSР 4: CCITT Signalling System No. 7 protocol layering and its relationship to OSI modelling;ЦЦ Та ТР-РТ№ ТРSР 5: Node, application entity and user part addressing;ЦЦ а H аТа ТР-РТ№ ТРSР 6: Operations, administration and maintenance aspects of CCITT S.S. No. 7;ЦЦ а H аТа ТР-РТ№ ТРSР 7: Performance aspects of the functional blocks within CCITT S.S. No. 7;ЦЦ а H аТа ТР-РТ№ ТРSР 8: Flow control for both the signalling network and within nodes;ЦЦ а H аТа ТР-РТ№ ТРSР 9: Rules for evolving CCITT S.S. No. 7 protocols while preserving compatibility with earlier versions;ЦЦ Та ТР-РТ№ ТРSР 10: A crossР-Рreference to a glossary of terms.ЦЦ а HH а1.1Тh  ТУУObjectives and fields of applicationЦЦ а H№ аФФС СThe overall objective of Signalling System No. 7 is to provide an internationally standardised general purpose common channel signalling (CCS) system: а H аТа ТР-РТ№ Тoptimised for operation in digital telecommunications networks in conjunction with stored program controlled exchanges;ЦЦ а H аТа ТР-РТ№ Тthat can meet present and future requirements of information transfer for interР-Рprocessor transactions within telecommunications networks for call control, remote control, and management and maintenance signalling;ЦЦ а H аТа ТР-РТ№ Тthat provides a reliable means for transfer of information in correct sequence and without loss or duplication.ЦЦа HH а а H аС СThe signalling system meets requirements of call control signalling for telecommunication services such as the telephone, ISDN and circuit switched data transmission services. It can also be used as a reliable transport system for other types of information transfer between exchanges and specialised centres in telecommunications networks (e.g. for management and maintenance purposes). The system is thus applicable for multipurpose uses in networks that are dedicated for particular services and in multiservices networks. The signalling system is intended to be be applicable in international and national networks. С СThe scope of CCITT S.S. No. 7 encompasses both circuit related and nonР-Рcircuit related signalling. С СExamples of applications supported by CCITT S.S. No. 7 are: Та ТР-РТ№ ТPSTN,ЦЦ Та ТР-РТ№ ТISDN,ЦЦ а H аТа ТР-РТ№ ТInteraction with Network Databases, Service Control Points for service control,ЦЦ Та ТР-РТ№ ТMobiles (Public Land Mobile Network),ЦЦ Та ТР-РТ№ ТOperations Administration and Maintenance of Networks.ЦЦ а H аС СThe signalling system is optimized for operation over 64Р-Рkbit/s digital channels. It is also suitable for operation over analogue channels and at lower speeds. The system is suitable for use on pointР-РtoР-Рpoint terrestrial and satellite links. It does not include the special features required for use in pointР-РtoР-Рmultipoint operation but can, if required, be extended to cover such an application. 1.2Тh  ТУУGeneral characteristicsЦЦ а H аФФС СCommon channel signalling is a signalling method in which a single channel conveys, by means of labelled messages, signalling information relating to, for example, a multiplicity of circuits, or other information such as that used for network management. Common channel signalling can be regarded as a form of data communication that is specialised for various types of signalling and information transfer between processors in telecommunications networks. а H аС СThe signalling system uses signalling links for transfer of signalling messages between exchanges or other nodes in the telecommunication network served by the system. Arrangements are provided to ensure reliable transfer of signalling information in the presence of transmission disturbances or network failures. These include error detection and correction on each signalling link. The system is normally applied with redundancy of signalling links and it includes functions for automatic diversion of signalling traffic to alternative paths in case of link failures. The capacity and reliability for signalling may thus be dimensioned by provision of a multiplicity of signalling links according to the requirements of each application. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТX  ТТX јТС€  СС€ HС1.3С   Сб cмˆ4 PŽТ бУУComponents of CCITT S.S. No. 7ЦЦ а H ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бФФС СCCITT S.S. No. 7 consists of a number of components or functions which are defined as a series of Q.700 to Q.795 Recommendations. вЦ‚HиPР!Цв‡ааУУС СCCITT S.S. No. 7 functionФФ УУRecommendationsФФ ˆвЦ‚HиPР!Цв‡УУС СФФMessage Transfer Part (MTP) Q.701Р-РQ.704, Q.706, Q.707 ˆвЦ‚HиPР!Цв‡УУС СФФTelephone User Part (TUP) (including supplementary services) Q.721Р-РQ.725 ˆвЦ‚HиPР!Цв‡УУС СФФSupplementary services Q.730 ˆвЦ‚HиPР!Цв‡УУС СФФData User Part (DUP) Q.741 (note 1) ˆвЦ‚HиPР!Цв‡УУС СФФISDN User Part (ISDNР-РUP) Q.761Р-РQ.764, Q.766 ˆвЦ‚HиPР!Цв‡УУС СФФSignalling Connection Control Part (SCCP) Q.711Р-РQ.714, Q.716 ˆвЦ‚HиPР!Цв‡УУС СФФTransaction Capabilities (TC) Q.771Р-РQ.775 ˆвЦ‚HиPР!Цв‡УУС СФФOperations Maintenance and Administration Part (OMAP) Q.795 ˆа H аС СУУNote 1ФФ Р-Р Functions of the DUP are fully specified in Recommendation X.61. а H аС СOther Q.700 to Q.795 series Recommendations which describe other aspects of the signalling system but not part of the CCITT S.S. No. 7 signalling interfaces are: б cмˆ4 PŽТ бвЦ‚HиPР!Цв‡аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`иџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бУУTitle аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHЈX Р!џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаRecommendationsФФ ˆа PА ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџPЈX Р!џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бвЦ‚HиPР!Цв‡а P ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџpи P Ј XА`иPџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бSignalling Network Structure аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџPЈX Р!џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаQ.705 а HH ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHЈX Р!џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаˆа PА ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџPЈX Р!џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бвЦ‚HиPР!Цв‡а P ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџpи P Ј XА`иPџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бNumbering of International Signalling Point Codes аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџPЈX Р!џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаQ.708 а HH ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHЈX Р!џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаˆа PА ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџPЈX Р!џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бвЦ‚HиPР!Цв‡а P ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџpи P Ј XА`иPџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бHypothetical signalling reference connection аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџPЈX Р!џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаQ.709 а HH ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHЈX Р!џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаˆа PА ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџPЈX Р!џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бвЦ‚HиPР!Цв‡аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџpи P Ј XА`иPџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бPABX application аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџPЈX Р!џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаQ.710 а HH ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHЈX Р!џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаˆа PА ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџPЈX Р!џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бвЦ‚HиPР!Цв‡а P ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџpи P Ј XА`иPџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бCCITT S.S. No. 7 Test Specification (General) аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџPЈX Р!џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаQ.780 а HH ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHЈX Р!џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаˆа PА ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџPЈX Р!џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бвЦ‚HиPР!Цв‡а P ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџpи P Ј XА`иPџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бMTP Level 2 Test Specification аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџPЈX Р!џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаQ.781 а HH ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHЈX Р!џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаˆа PА ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџPЈX Р!џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бвЦ‚HиPР!Цв‡а P ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџpи P Ј XА`иPџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бMTP Level 3 Test Specification аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџPЈX Р!џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаQ.782 а HH ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHЈX Р!џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаˆа PА ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџPЈX Р!џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бвЦ‚HиPР!Цв‡а PX ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџpи P Ј XА`иPџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бTUP Test Specification аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџPЈX Р!џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаQ.783 а HH ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHЈX Р!џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаˆа PА ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџPЈX Р!џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бвЦ‚HиPР!Цв‡а P ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџpи P Ј XА`иPџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бMonitoring and measurements for the CCITT S.S. No.7 network аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџPЈX Р!џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаQ.791 а HH ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHЈX Р!џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаˆа PА ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџPЈX Р!џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бвЦ‚HиPР!Цв‡а P ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџpи P Ј XА`иPџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бРSР 3 of Q.700 describes the relationship between these components. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџPЈX Р!џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬа а HH ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHЈX Р!џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаˆа H ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТа Т1.4СpСУУDescription techniques in the Q.700 to Q.795 series of RecommendationsЦЦ а H аФФС СThe CCITT S.S. No. 7 Recommendation series define the signalling system using prose description which is complemented by SDL diagrams and state transition diagrams. Should any conflict arise between the text and the SDL definition, the textual description is taken as definitive. а H аС СMessage sequence charts or arrow diagrams are used to illustrate examples of signalling procedures, but are not considered definitive. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТX  ТТX јТС€  СС€ HС‚У У2С  СCCITTб cмˆ4 PŽТ б S.S. No. 7 signalling networkЦЦ аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бФ Ф2.1Тh  ТУУBasic conceptsЦЦ ФФС СA telecommunications network served by common channel signalling is composed of a number of switching and processing nodes interР-Рconnected by transmission links. To communicate using CCITT No. 7, each of these nodes requires to implement the necessary Р"Рwithin nodeР"Р features of CCITT S.S. No. 7 making that node a signalling point within the CCITT S.S. No. 7 network. In addition, there will be a need to interconnect these signalling points such that CCITT S.S. No. 7 signalling information (data) may be conveyed between them. These data links are the signalling links of CCITT S.S. No. 7 signalling network. а H аС СThe combination of signalling points and their interconnecting signalling links form the CCITT S.S. No. 7 signalling network. 2.2Тh  ТУУSignalling network componentsЦЦ аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТX  ТТX јТС€  СС€ HСФФ2.2.1С јСб cмˆ4 PŽТ бУУSignalling pointsЦЦ аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бФФС СIn specific cases there may be a need to partition the common channel signalling functions at such a (physical) node into logically separate entities from a signalling network point of view; i.e., a given (physical) node may be defined as more than one signalling point. One example is an exchange at the boundary between international and national signalling networks. С СAny two signalling points, for which the possibility of communication between their corresponding User Part function exists, are said to have a signalling relation. С СThe corresponding concept for a given User Part is called a user signalling relation. а H аС СAn example is when two telephone exchanges are directly connected by a bundle of speech circuits. The exchange of telephone signalling relating to these circuits then constitutes a user signalling relation between the Telephone User Part functions in those exchanges in their role as signalling points. а H аС СAnother example is when administration of customer and routing data in a telephone exchange is remotely controlled from an operation and maintenance centre by means of communication through a common channel signalling system. С СExamples of nodes in a signalling network that constitutes signalling points are: Та ТР-РТ№ Тexchanges (switching centres),ЦЦ Та ТР-РТ№ Тoperation, administration and maintenance centres,ЦЦ Та ТР-РТ№ Тservice control points,ЦЦ Та ТР-РТ№ Тsignalling transfer points.ЦЦ а H аС СAll signalling points in a CCITT S.S. No. 7 network are identified by a unique code known as a point code (Recommendation Q.704 refers). аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТX  ТТX јТС€  СС€ HС2.2.2С јСб cмˆ4 PŽТ бУУSignalling linksЦЦ а H ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бФФС СThe common channel signalling system uses signalling links to convey the signalling messages between two signalling points. A number of signalling links that directly interconnect two signalling points which are used as a module constitute a signalling linkР-Рset. Although a link set typically includes all parallel signalling links, it is possible to use more than one link set in parallel between two signalling points. A group of links within a link set that have identical characteristics (e.g., the same data link bearer rate) is called a link group. а H аС СTwo signalling points that are directly interconnected by a signalling link are, from a signalling network structure point of view, referred to as adjacent signalling points. Correspondingly, two signalling points that are not directly interconnected are nonР-Рadjacent signalling points. Та ТС€ HС2.2.3С СУУSignalling modesЦЦ ФФС СThe term Р"Рsignalling modeР"Р refers to the association between the path taken by a signalling message and the signalling relation to which the message refers. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаС  СIn the associated modeй<€ associated modeб cмˆ4 PŽТ б<й of signalling, the messages relating to a particular signalling relation between two adjacent points are conveyed over a link set, directly interconnecting those signalling points. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаС СIn the nonР-Рassociated mode of signalling, the messages relating to a particular signalling relation are conveyed over two or more linksets in tandem passing through one or more signalling points other than those which are the origin and the destination of the messages. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаС  СThe quasiР-Рassociated modeй  quasiР-Рassociated mode йб cмˆ4 PŽТ б of signalling is a limited case of the nonР-Рassociated mode where the path taken by the message through the signalling network is preР-Рdetermined and, at a given point in time, fixed. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаС СSignalling System No. 7 is specified for use in the associated and quasiР-Рassociated modes. The Message Transfer Part does not include features to avoid outР-РofР-Рsequence arrival of messages or other problems that would typically arise in a fully nonР-Рassociated mode of signalling with dynamic message routing. С СExamples of signalling modes are illustrated in Figure 1/Q.700. ‚Ср KСб cмˆ4 PŽТ бFigure 1/Q.700 Љ CCITTЉ34960 б cмˆ4 PŽТ б 2.3Тh  ТУУSignalling point modesЦЦ а H аФФС СA signalling point at which a message is generated, i.e., the location of the source User Part function, is the originating point of that message. а H аС СA signalling point to which a message is destined, i.e., the location of the receiving User Part function, is the destination point of that message. а H аС СA signalling point at which a message is received on a signalling link is transferred to another link, i.e., neither the location of the source nor the receiving User part function, is a Signal Transfer Point (STP). С СFor a particular signalling relation, the two signalling points thus function as originating and destination points for the messages exchanged in the two directions between them. а H аС СIn the quasiР-Рassociated mode, the function of a signalling transfer point is typically located in a few signalling points which may be dedicated toд Д-д this function, or may combine this function with some other (e.g., switching) function. A signalling point serving as a signalling transfer point functions as an originating and destination point for the messages generated and received by the level 3 function of the Message Transfer Point also in cases when no user functions are present. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТX  ТТX јТС€  СС€ HС2.4С   Сб cмˆ4 PŽТ бУУSignalling routesЦЦ аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бФФС СThe preР-Рdetermined path, consisting of a succession of signalling points/signalling transfer points and the interconnecting signalling links, а H аthat a message takes through the signalling network between the origination point and the destination point is the signalling route for that signalling relation. а H аС СAll the signalling routes that may be used between an originating point and a destination point by a message traversing the signalling network is the signalling route set for that signalling relation. 2.5Тh  ТУУSignalling network structureЦЦ ФФС СThe signalling system may be used with different types of signalling network structures. The choice between different types of signalling network structures may be influenced by factors such as the structure of the telecommunication network to be served by the signalling system and administrative aspects. а H аС СIn the case when the provision of the signalling system is planned purely on a per signalling relation basis, the likely result is a signalling network largely based on associated signalling, typically supplemented by a limited degree of quasiР-Рassociated signalling for low volume signalling relations. The structure of such a signalling network is mainly determined by the patterns of the signalling relations. С СAnother approach is to consider the signalling network as a common resource that should be planned according to the total needs for common а H аchannel signalling. The high capacity of digital signalling links in combination with the needs for redundancy for reliability then typically leads to a signalling network based on a high degree of quasiР-Рassociated signalling with some provision for associated signalling for high volume signalling relations. The latter approach to signalling network planning is more likely to allow exploitation of the potential of common channel signalling to support network features that require communication for purposes other than the switching of connections. С СThe worldwide signalling network is structured into two functionally independent levels, namely the international and national levels. This structure makes possible a clear division of responsibility for signalling network management and allows numbering plans of signalling points of the international network and the different national networks to be independent of one another. а H аС СFurther considerations about the structure of the signalling network are given in Recommendation Q.705, and the impact on the message transfer part in Recommendation Q.701. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТX  ТТX јТС€  СС€ HС‚У У3С  Сб cмˆ4 PŽТ бCCITT S.S. No. 7 functional blocksЦЦ аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бФ Ф3.1Тh  ТУУBasic functional divisionЦЦ ФФС СThe Blue Book CCITT Signalling System No. 7 comprises the following functional blocks: Та ТР-РТ№ ТMessage Transfer PartС$А*СС*/СС/`4С(MTP)ЦЦ Та ТР-РТ№ ТTelephone User PartС"X%СС%А*СС*/СС/`4С(TUP)ЦЦ Та ТР-РТ№ ТISDN User PartС СС X%СС%А*СС*/С(ISDNР-РUP)ЦЦ Та ТР-РТ№ ТSignalling Connection Control PartС1`4СС4И9С(SCCP)ЦЦ Та ТР-РТ№ ТTransaction CapabilitiesС'А*СС*/СС/`4С(TC)ЦЦ Та ТР-РТ№ ТApplicationР-РEntityС!X%СС%А*СС*/СС/`4С(AE)УУ Note 1ФФЦЦ Та ТР-РТ№ ТApplicationР-РServiceР-РElementsС+/СС/`4С(ASEs)УУ Note 1ФФЦЦ а H аС СУУNote 1ФФ Р-Р The glossary shows these as hyphenated terms but the usual convention used in this Recommendation will be unhyphenated. С СThe fundamental principle of the signalling system structure is the division of functions into a common Message Transfer Part (MTP) on one hand, and separate User Parts for different users on the other. This is illustrated in Figure 2/Q.700. С СThe overall function of the Message Transfer Part is to serve as a transport system providing reliable transfer of signalling messages between the locations of communicating user functions. С СUser functions in CCITT S.S. No. 7 MTP terms are: Та ТР-РТ№ Тthe ISDN User PartС!X%СС%А*СС*/СС/`4С(ISDNР-РUP)ЦЦ Та ТР-РТ№ Тthe Telephone User PartС&А*СС*/СС/`4С(TUP)ЦЦ Та ТР-РТ№ Тthe Signalling Connection Control PartС5И9С(SCCP)ЦЦ Та ТР-РТ№ Тthe Data User PartС!X%СС%А*СС*/СС/`4С(DUP)ЦЦ а H аС СThe term Р"РUserР"Р in this context refers to any functional entity that utilises the transport capability provided by the Message Transfer Part. а H аС СA User Part comprises those functions of, or related to, a particular type of user that are part of the common channel signalling system, typically because those functions need to be specified in a signalling context. С СThe SCCP also has Users. These are: Та ТР-РТ№ Тthe ISDN User PartС!X%СС%А*СС*/СС/`4С(ISDNР-РUP)ЦЦ Та ТР-РТ№ ТTransaction CapabilitiesС'А*СС*/СС/`4С(TC)ЦЦ а HH а‚Ср8DСб cмˆ4 PŽТ бFigure 2/Q.700 Љ T1109720Љ88 б cмˆ4 PŽТ б аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТX  ТТX јТС€  СС€ HС3.2С   Сб cмˆ4 PŽТ бУУCCITT S.S. No. 7 architectureЦЦ аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТа ТС€ HСб cмˆ4 PŽТ бФФ3.2.1С СУУGeneralЦЦ а H аФФС СFigure 2/Q.700 shows the Architecture of CCITT S.S. No. 7 and illustrates the functional relationship between the various functional blocks of the Blue Book CCITT S.S. No. 7. Figure 5/Q.700 shows the relationship between CCITT No. 7 levels and the OSI Reference Model Layers. This level/layer relationship is described in the following sections. С СThe initial specification of CCITT No. 7 was based on circuitР-Рrelated telephony control requirements. To meet these requirements, CCITT No. 7 was specified in four functional levels, the Message Transfer Part comprising levels 1Р-Р3, and the User Parts as level 4. а H аС СFigure 3/Q.700 shows the Functional Levels of CCITT S.S. No. 7. As new requirements have emerged, e.g., for nonР-Рcircuit related information transfer, CCITT S.S. No. 7 has also evolved to meet these new requirements. There has been a need to align certain elements in CCITT No. 7 to the OSI 7 Layer Reference Model. С СThe result of this evolution is that Functional Levels and OSI layers coР-Рexist in CCITT No. 7. For example, the SCCP is a level 4 User Part in MTP terms, but also provides an OSI Network layer 3 service. Subsequent sections describe the various functional elements of CCITT S.S. No. 7 in terms of levels and layers. ‚Ср KСб cмˆ4 PŽТ бFigure 3/Q.700 Љ T1109730Љ88 б cмˆ4 PŽТ б а H аС СIt should be noted that the approach proposed for ISDN architecture is to define two orthogonal planes, User and Control, each of which has its own 7Р-Рlayer protocol reference model. С СFrom the perspective of an end user, the service provided by a telecommunications network may be regarded as a Network Layer Service (User Plane). а H аС СWithin the telecommunications network, the techniques of the ISDN Protocol Reference Model are applied, and the 7Р-Рlayer protocol structure of the OSI Model can also be used for interР-Рnodal communication to the end user. Та ТС€ HС3.2.2С СУУMessage Transfer Part (MTP) levels 1Р-Р3ЦЦ ФФС СAn overview of the MTP is given in Recommendation Q.701. The MTP is defined in Recommendations Q.701Р-РQ.704, Q.706 and Q.707. Та Т3.2.2.1СP Сб cмˆ4 PŽТ бУУSignalling data link functions (level 1)ЦЦ а H аб cмˆ4 PŽТ бФФС СLevel 1 defines the physical, electrical and functional characteristics of a signalling data link and the means to access it. The level 1 element provides a bearer for a signalling link. а H аС СIn a digital environment, 64Р-Рkbit/s digital paths will normally be used for the signalling data link. The signalling data link may be accessed via a switching function, providing a potential for automatic reconfiguration of signalling links. Other types of data links, such as analogue links with modems, can also be used. С СThe detailed requirements for signalling data links are specified in Recommendation Q.702. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТX  ТТX јТС€  СС€ HС3.2.2.2СјСб cмˆ4 PŽТ бУУSignalling link functions (level 2)ЦЦ аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бФФС СLevel 2 defines the functions and procedures for and relating to the transfer of signalling messages over one individual signalling data link. а H аThe level 2 functions together with a level 1 signalling data link as a bearer, and provides a signalling link for reliable transfer of signalling messages between two points. а H аС СA signalling message delivered by the higher levels is transferred over the signalling link in variable length signal units. For proper operation of the signalling link, the signal unit comprises transfer control information in addition to the information content of the signalling message. С СThe detailed requirements for signalling functions are given in Recommendation Q.703. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТX  ТТX јТС€  СС€ HС3.2.2.3СјСб cмˆ4 PŽТ бУУSignalling network functions (level 3)ЦЦ а H ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бФФС СLevel 3 in principle defines those transport functions and procedures that are common to and independent of the operation of individual signalling links. These functions fall into two major categories: а H аТа ТТ№ ТС€ Сa)СpСSignalling message handling functions Р-Р These are functions that, at the actual transfer of the message, direct the message to the proper signalling link or User Part.ЦЦ а H аТа ТТ№ ТС€ Сb)СpСSignalling network management functions Р-Р These are functions that, on the basis of predetermined data and information about the status of the signalling network, control the current message routing and configuration of the signalling network facilities. In the event of changes in the status, they also control the reconfigurations and other actions to preserve or restore the normal message transfer capability.ЦЦ а H аС СThe detailed requirements for signalling network functions are given in Recommendation Q.704. Та ТС€ HС3.2.3С СУУLevel 4: MTP User functionsЦЦ а H аФФС СLevel 4 consists of the different User Parts. Each User Part defines the functions and procedures of the signalling system that are particular to a certain type of user of the system. the following entities are defined as User Parts in CCITT S.S. No. 7. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТX  ТТX јТС€  СС€ HС3.2.3.1СјСб cмˆ4 PŽТ бУУSignalling Connection Control Part (SCCP)ЦЦ а H ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бФФС СThe SCCP is defined in Recommendations Q.711Р-РQ.716. This Recommendation series defines the SCCP capabilities, layer interfaces to MTP and SCCP а H аusers signalling messages, their encoding and signalling procedures, and crossР-Рoffice performance. The SCCP provides additional functions to the Message Transfer Part to provide such connectionless and connectionР-Рoriented network services to transfer circuitР-Рrelated, and nonР-РcircuitР-Рrelated signalling information. С СThe SCCP provides the means to: а H№ аТа ТР-РТ№ Тcontrol logical signalling connections in a CCITT No. 7 network;ЦЦ а H аТа ТР-РТ№ ТTransfer Signalling Data Units across the CCITT No. 7 network with or without the use of logical signalling connections.ЦЦ а H аС СSCCP provides a routing function which allows signalling messages to be routed to a signalling point based on, for example, dialled digits. This capability involves a translation function which translates the global title (e.g., dialled digits) into a signalling point code and a subsystem number. а H аС СSCCP also provides a management function, which controls the availability of the Р"РsubsystemsР"Р, and broadcasts this information to other nodes in the network which have a need to know the status of the Р"РsubsystemР"Р. а H аС СThe combination of the MTP and the SCCP is called Р"РNetwork Service PartР"Р (NSP). The Network Service Part meets the requirements for layer 3 services as defined in the OSIР-РReference Model, CCITT Recommendation X.200. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТX  ТТX јТС€  СС€ HС3.2.3.2СјСб cмˆ4 PŽТ бУУTelephone User Part (TUP)ЦЦ а H ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бФФС СThe CCITT S.S. No. 7 Telephone User Part is defined in Recommendations Q.721Р-Р725. The TUP Recommendations define the necessary telephone signalling functions for use of S.S. No. 7 for international telephone call control signalling. This Recommendation series defines the telephone signalling messages, their encoding and signalling procedures, and crossР-Рoffice performance. а H аС СSupplementary Services handled by the CCITT S.S. No. 7 TUP applications are described in Recommendation Q.724, РSР 10. These supplementary services embody TUP signalling messages and procedures. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТX  ТТX јТС€  СС€ HС3.2.3.3СјСб cмˆ4 PŽТ бУУData User Part (DUP)ЦЦ аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бФФС СThe Data User Part is defined in Recommendation Q.741, and the functionality fully defined in Recommendation X.61. It defines the protocol to control interexchange circuits used on data calls, and data call facility registration and cancellation. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТX  ТТX јТС€  СС€ HС3.2.3.4СјСб cмˆ4 PŽТ бУУISDN User Part (ISDNР-РUP)ЦЦ а H ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаФФб cмˆ4 PŽТ бС СThe ISDN User Part is defined in Recommendations Q.761Р-РQ.764 and Q.766. This Recommendation series defines the ISDN network signalling messages, their encoding and signalling procedures, and crossР-Рoffice performance. This Recommendation series deals with the basic services only. а H аС СThe ISDNР-РUP encompasses signalling functions required to provide switched services and user facilities for voice and nonР-Рvoice applications in the ISDN. С СThe ISDNР-РUP is also suited for application in dedicated telephone and circuitР-Рswitched data networks and in analogue, and mixed analogue/digital networks. а H аС СThe ISDNР-РUP has an interface to the SCCP (which is also a level 4 User Part) to allow the ISDNР-РUP to use the SCCP for endР-РtoР-Рend signalling. а H аС СSupplementary Services handled by the CCITT S.S. No. 7 ISDN application are described in Recommendation Q.730. These supplementary services embody ISDNР-РUP signalling messages and procedures. In some cases these services а H аalso include application protocol which uses TC and SCCP, as, for example, centralised Closed User Group (CUG). аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТX  ТТX јТС€  СС€ HС3.2.3.5СјСб cмˆ4 PŽТ бУУTransaction CapabilitiesЦЦ а H ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бФФС СTransaction Capabilities is defined in Recommendations Q.771Р-РQ.775. This Recommendation series defines the Transaction Capabilities signalling messages, their encoding and signalling procedures. С СTransaction Capabilities consists of two elements. These are: Та ТР-РТ№ ТTransaction Capabilities Application Part (TCAP);ЦЦ а H аТа ТР-РТ№ ТIntermediate Service Part (ISP) [The ISP is for further study (see Note 1, Figure 5/Q.700)].ЦЦ а H аС СThe TCAP entity is a functional block residing above the ISP in layer 7. TCAP consists of two subР-Рlayers: the Transaction subР-Рlayer, and the Component subР-Рlayer. Further details are given in Recommendation Q.771. а H аС СTC, as currently specified, provides services based on a connectionless network service. In this case, no ISP layers 4Р-Р6 functions are involved. ConnectionР-Рoriented TC services, and the layer functions of layers 4Р-Р6 are for further study. С СTC provides the means to establish nonР-РcircuitР-Рrelated communication between two nodes in the signalling network. а H аС СTC provides the means to exchange operations and replies via a dialogue. The X.229 Remote Operations protocol has been extended to provide added functionality in order to accommodate specific user needs. The operations and parameters are part of the Application protocol between TC users. Та Т3.2.3.6СP Сб cмˆ4 PŽТ бУУApplication Entities and Application Service ElementsЦЦ а H аб cмˆ4 PŽТ бФФС СIn an OSI environment, communication between application processes is modelled by communication between Р"РApplication Entities (AEs)Р"Р. An Application Entity represents the communication functions of an Application process. There may be multiple sets of OSI communication functions in an application process, so a single application process may be represented by multiple AEs. However, each Application Entity is a set of communication capabilities whose components are Р"РApplication Service ElementsР"Р. An Application Service Element (ASE) is a coherent set of integrated functions. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТX  ТТX јТС€  СС€ HС3.2.3.6.1СP Сб cмˆ4 PŽТ бУУApplication Entities in a CCITT S.S. No. 7 environmentЦЦ а H ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бФФС СFigure 4/Q.700 shows the relationship between Application Processes and Application Entities, and Application Service Elements. С СAn Р"РApplication ProcessР"Р is considered to be a range of functions and features which support a particular network requirement. For example, an application process in the context of CCITT S.S. No. 7 provides the coР-Рordination across circuitР-Рrelated protocols where required. С СAn Application Process can be considered as: а H аТа ТТ№ ТС€ Сa)СpСa coР-Рordinator of specific aspects of network operation (e.g., ISDN Call Control, Mobiles, OA&M);ЦЦ а H аТа ТТ№ ТС€ Сb)СpСan individual service or supplementary service control function (e.g., CUG).ЦЦ а H аС СIn the CCITT S.S. No. 7 context, the various functional elements of the signalling system provide the signalling protocols (information elements, messages, and procedures) necessary to support the service between nodes. а H аС СIn a CCITT No. 7 environment, Application Entities (AEs) are the elements representing the communication functions of the application process, which are pertinent to interР-Рnodal communication using layer 7 application protocols. а H аС СThe options for the relationship between an application process, AEs and ASEs can take several forms at a CCITT No. 7 signalling point. Some examples are shown in Figure 4/Q.700. ‚Ср KСб cмˆ4 PŽТ бFigure 4/Q.700 Љ T1109742Љ88 б cмˆ4 PŽТ б 3.2.3.6.2СpСУУApplication Service Elements in a CCITT No. 7 environmentФФ С СApplication Service Elements (ASEs) reside in the CCITT S.S. No. 7 Architecture Model within layer 7 above TCAP. In the context of OSI, TCAP could also be considered to be an ASE. а H аС СOMAP has an Application Entity currently containing the TCAP ASE and one other ASE. Other ASEs are under study. OMAP is described further in РSР 6. а H аС СThe Mobile Application Part (MAP) is another example of an Application Entity (AE) (see Recommendation Q.1051). а H аС СAn ASE can include a number of signalling procedures for a single service (e.g., Freephone), where this single service is the application. а H аС СAlternatively, an ASE can include a number of signalling procedures for any number of services or functions, encompassed by an application (e.g., MAP, OMAP). а H аС СThus, an ASE can define an individual service protocol (e.g., CUG), or a complete application protocol (e.g., MAP). а H аС СAn ASE can only communicate with a compatible peer ASE. The operations defined in an ASE may be either symmetrically invoked by each entity involved in the dialogue, or asymmetrically invoked by one entity only (i.e., on a Р"Рclient/serverР"Р basis). An example of the former is a Р"Рlook ahead if freeР"Р procedure; an example of the latter is a database enquiry. Та ТС€ HС3.2.3.6.3СpСУУAddressing for Application Entities (AEs)ЦЦ а H аФФС СThe SCCP provides a mechanism for addressing Р"РsubsystemsР"Р using Subsystem Numbers (SSNs). The Application Entity is considered, in the connectionless mode, equivalent to an SCCP subsystem. Та ТС€ HС3.2.3.6.4СpСУУManagement of AEsЦЦ а H аФФС СThe SCCP provides a mechanism for managing Р"РsubsystemsР"Р and signalling points and informing other nodes of relevant availability status. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТX  ТТX јТС€  СС€ HС‚У У4С  Сб cмˆ4 PŽТ бOSI layering and CCITT S.S. No. 7ЦЦ аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бФ Ф4.1Тh  ТУУGeneralЦЦ а H аФФС СEvolution of the CCITT Signalling System No. 7 architecture has been based on the Open Systems Interconnection (OSI) Reference Model. а H аС СThe purpose of the Reference Model of Open Systems Interconnection for CCITT Applications (Recommendation X.200) is to provide a wellР-Рdefined structure for modelling the interconnection and exchange of information between users in a communications system. This approach allows standardised procedures to be defined not only to provide an open systems interconnection between users over a single network, but also to permit interworking between networks to allow communication between users over several networks in tandem. а H аС СAt present, OSI only considers connectionР-Рoriented protocols, that is, protocols which establish a logical connection before transferring data. In CCITT S.S. No. 7, the ISDNР-РUP uses the SCCP connectionР-Рoriented protocol. The CCITT S.S. No. 7 Network Service Part (NSP) provides both connectionless and connectionР-Рoriented protocol. а H аС СThe approach taken in the OSI reference model is to partition the model used to describe this interconnection and exchange information between users in a communications system into seven layers. а H аС СFrom the point of view of a particular layer, the lower layers provide a Р"Рtransfer serviceР"Р with specific features. The way in which the lower layers are realised is immaterial to the next higher layers. Correspondingly, the lower layers are not concerned with the meaning of the information coming from higher layers or the reasons for its transfer. С СThe characteristics of each layer are described below. Та Т4.1.1Си СУУPhysical LayerЦЦ а H аФФС СThe Physical Layer (layer 1) provides transparent transmission of a bit stream over a circuit built in some physical communications medium. It furnishes the interface to the physical media and is responsible for relaying bits (i.e., interconnects dataР-Рcircuits). A 64 kbit/s link is assumed for the CCITT S.S. No. 7 Physical Layer. Та ТС€ HС4.1.2С СУУData Link LayerЦЦ а H аФФС СThe Data Link Layer (layer 2) overcomes the limitations inherent in the physical circuits and allows errors in transmission to be detected and recovered, thereby masking deficiencies in transmission quality. Та ТС€ HС4.1.3С СУУNetwork LayerЦЦ а H аФФС СThe Network Layer (layer 3) transfers data transparently by performing routing and relaying of data between end users. One or more of the subР-Рnetworks may interwork at the Network Layer to provide an end user to end user network service. A connectionless network provides for the transfer of data between end users, making no attempt to guarantee a relationship between two or more data messages from the same user. Та ТС€ HС4.1.4С СУУTransport LayerЦЦ ФФС СThe Transport Layer (layer 4) provides end user to end user transfer optimising the use of resources (i.e., network service) according to the type and character of the communication, and relieves the user of any concern for the details of transfer. The Transport Layer always operates endР-РtoР-Рend, enhancing the Network Layer when necessary to meet the quality of service objectives of the users. Та ТС€ HС4.1.5С СУУSession LayerЦЦ ФФС СThe Session Layer (layer 5) coР-Рordinates the interaction within each association between communicating application processes. Full and half duplex dialogues are examples of possible Session Layer modes. Та ТС€ HС4.1.6С СУУPresentation LayerЦЦ а H аФФС СThe Presentation Layer (layer 6) transforms the syntax of the data which is to be transferred into a form recognizable by the communicating application processes. For example, the Presentation Layer may convert a data stream from ASCII to EBCDIC. Та ТС€ HС4.1.7С СУУApplication LayerЦЦ а H аФФС СThe Application Layer (layer 7) specifies the nature of the communication required to satisfy the users' needs. This is the highest layer in the Model and so does not have a boundary with a higher layer. The Application Layer provides the sole means for the application processes to access the OSI environment. 4.2Тh  ТУУRelationship between CCITT S.S. No. 7 layering and the OSI modelЦЦ а H аФФС СLayers 1Р-Р3 comprise functions for the transportation of information from one location to another, possibly via a number of communication links in tandem. These functions provide the basis on which a communication network can be built. Та ТР-РТ№ ТThe SCCP provides, with the MTP, OSI layer services 1Р-Р3.ЦЦ а H аС СLayers 4Р-Р7 define functions relating to endР-РtoР-Рend communication. These layers are so defined that they are independent of the internal structure of the communication network. Та ТР-РТ№ ТTransaction Capabilities provides layer 4Р-Р7 services.ЦЦ а H аС СLayer 7 represents the semantics of a communication, whereas layers 1Р-Р6 comprise the means by which the communication may be realised. а Hр аТа ТР-РТ№ ТApplication Entities/Application Service Elements provide the appropriate Application Layer Protocols in layer 7.ЦЦ а H аС СFigure 5/Q.700 shows the relationship between SCCP, TC, and ASEs to the OSI 7 Layer Reference Model.‚б cмˆ4 PŽТ б Ср KСFigure 5/Q.700 Љ T1109751Љ88 б cмˆ4 PŽТ б а H аС СThe aspect of the SMAP which is then involved with communication is the Systems Management Application Entity (SMAE). The SMAE is also known as the OMAP AE. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТX  ТТX јТС€  СС€ HС4.3С   Сб cмˆ4 PŽТ бУУPrimitive Interfaces between CCITT No. 7 FunctionsЦЦ аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТа ТС€ HСб cмˆ4 PŽТ бФФ4.3.1С СУУGeneralЦЦ ФФС СInterfaces between the functional elements of CCITT S.S. No. 7 are specified using interface primitives. Primitive interface definition does not assume any specific implementation of a service. Та ТС€ HС4.3.2С СУУOSI service primitivesЦЦ а H аФФС СWhere the functional element of CCITT No. 7 is modelled on the OSI 7 layer reference model, e.g., SCCP, TC, service primitives are defined in line with Recommendation X.210. С СIn line with Recommendation X.210, Figure 6/Q.700 illustrates the relationship between the terms Р"РserviceР"Р, Р"РboundaryР"Р, Р"Рservice primitivesР"Р, Р"Рpeer protocolР"Р and Р"Рpeer entitiesР"Р. The term Р"РboundaryР"Р applies to boundaries between layers, as well as to boundaries between subР-Рlayers. ‚Ср KСб cмˆ4 PŽТ бFigure 6/Q.700 Љ T1109760Љ88 б cмˆ4 PŽТ б Та ТС€ HС4.3.2.1СpСУУService primitivesЦЦ а H аФФС СThe user of primitives does not preclude any specific implementation of a service in terms of interface primitives. а H аС СA service primitive consists of a name and one or more parameters which are passed in the direction of service primitive. а H аС СThe name of a service primitive contains three elements, as defined in Recommendation X.210: а H аТа ТТ№ ТС€ Сa)СpСa type indicating the direction of the primitive flow. Four types of service primitives are identified (Figure 7/Q.700):ЦЦ а H аТа ТТ№ ТР-РТhpТrequestСЈ Сa primitive issued by a service user to invoke a service element,ЦЦ а H аТа ТТ№ ТТhpТТhи ТТаЈ ТС€и СС€pСС€СР-РСpСindicationС Сa primitive issued by a service provider to advise that a service element has been invoked by the service user at the peer service access point or by the service provider,ЦЦ а H аТа ТТ№ ТТhpТТhи ТТаЈ ТС€и СС€pСС€СР-РСpСresponseС Сa primitive issued by the service user to complete at a particular service access point some service element whose invocation has been previously indicated at that service access point,ЦЦ Та ТТ№ ТТhpТТhи ТТаЈ ТС€и СС€pСС€СР-РСpСconfirmationС Сa primitive issued by a service provider to complete at a particular service access pointЦЦ а H аТа ТТ№ ТТhpТТhи ТТаЈ Тsome service element previously invoked by a request at that service access point.ЦЦ Та ТТ№ ТС€ СNot all four types can be associated with all service names.ЦЦ Та ТТ№ ТС€ Сb)СpСa name which specifies the action to be performed;ЦЦ а H аТа ТТ№ ТС€ Сc)СpСAn initial (or initials) which specifies the (subР-Р)layer providing the service:ЦЦ а H аТа ТТ№ ТР-РТhpТOM for the Operations Management primitives associated with OMAP;ЦЦ Та ТТ№ ТР-РТhpТTC for the TCAP Component subР-Рlayer,ЦЦ Та ТТ№ ТР-РТhpТTR for the TCAP Transaction subР-Рlayer,ЦЦ а H аТа ТТ№ ТР-РТhpТP, S, T, respectively for the Presentation, Session, and Transport layers in the ISP,ЦЦ а Hр аТа ТТ№ ТР-РТhpТN for the Network Service Part (MTP + SCCP), as defined in Recommendation Q.711.ЦЦа HH а‚б cмˆ4 PŽТ б Ср8DСFigure 7/Q.700 Љ T1109771Љ88 б cмˆ4 PŽТ б а H аС СFigure 8/Q.700 provides an overview of the primitives used between the various functional elements of CCITT No. 7. С СThe MTP primitives apply to all level 4 users of the MTP. С СSimilarly, the SCCP Management Primitives NР-РSTATE, NР-РCOORD, NР-РPCSTATE apply to all SCCP subsystems/AEs via TC. а H аС СThe TC primitives between the ASE and TC provide control of connectionless TCAP transactions. Service primitives for connectionР-Рoriented TC transactions are for further study. ‚Ср KСб cмˆ4 PŽТ бFigure 8/Q.700 Љ T1109780Љ88 б cмˆ4 PŽТ б аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТX  ТТX јТС€  СС€ HСУ У5С  Сб cмˆ4 PŽТ бAddressingЦЦ а H ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бФ ФС СAddressing of CCITT S.S. No. 7 messages has to be considered on a number of levels. For example, the message transfer part uses the destination point code to route the message to the appropriate signalling point. The called party address field in TUP, or ISUP called party number field, in the Initial Address Message is used to route the call to the appropriate called destination. The capabilities of the various CCITT S.S. No. 7 addressing mechanisms are illustrated by the signalling message structure. 5.1Тh  ТУУSignalling message structureЦЦ а H аФФС СA signalling message is an assembly of information, defined at level 3 or 4, pertaining to a call, management transaction, etc., that is transferred as an entity by the message transfer function. а H аС СEach message contains service information including a service indicator identifying the source User Part and possibly additional information such as an indication whether the message relates to international or national application of the User Part. С СThe signalling information of the message includes the actual user information, such as one or more telephone or data call control signals, management and maintenance information, etc., and information identifying the type and format of the message. It also includes a label that provides information enabling the message to be: а H аТа ТР-РТ№ Тrouted by the level 3 functions and thorugh a signalling network to its destination; and (This part of the label is known as the Routing label. This is shown in Figure 9/Q.700.)ЦЦ а H аТа ТР-РТ№ Тdirected at the receiving User Part to the particular circuit, call, management or other transaction to which the message is related.ЦЦ а HH аС СFurther details are given in Q.700, РSР 5.2. б cмˆ4 PŽТ бвЦƒHИ Ј XЦв‡аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬа‚Ср8QСб cмˆ4 PŽТ бSLS аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH` Ш 0 ˜ џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаСр8LСOriginating Ср8MСPoint Code Ср8LСDestination Ср8MСPoint Code а Ј  ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџ` Ш 0 Ј ˜ џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бˆа HH ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаСр8KСб cмˆ4 PŽТ бFIGURE 9/Q.700У У Ср8DСCCITT SS No. 7 Routing Label б cмˆ4 PŽТ бФ ФС СThere are four types of label: Та ТР-РТ№ Тtype A for MTP management messages;ЦЦ Та ТР-РТ№ Тtype B for TUP;ЦЦ Та ТР-РТ№ Тtype C for ISDNР-РUP (circuit related) messages;ЦЦ Та ТР-РТ№ Тtype D for SCCP messages.ЦЦ С СThese are shown in Figure 10/Q.700. а H аС СThe circuit identification code is used as a label for circuit related signalling messages, e.g., TUP or ISDNР-РUP. The least significant 4 bits of this field (in the TUP) is the Signalling Link Selection (SLS) field, which is used, where appropriate, to perform load sharing (see Q.704). In the ISDNР-РUP, the SLS is a separate field to the circuit identification code. С СThe CCITT No. 7 MTP signalling messages at level 2, which carry user information, are called Message Signal Units (MSUs). Figure 11/Q.700 shows the basic format of the MSU (refer also to Q.703) and the breakdown of the MSU. Signalling Information Field (SIF) when transporting circuitР-Рrelated (ISDNР-РUP, TUP) messages and nonР-РcircuitР-Рrelated messages (SCCP, TC based). Further details are given on message formats in Recommendations Q.704, Q.713, Q.723, Q.763, Q.773.‚б cмˆ4 PŽТ б Ср KСFigure 10/Q.700 Љ T1109791Љ88 б cмˆ4 PŽТ б Ср KСб cмˆ4 PŽТ бFigura 11/Q.700 Љ T1109801Љ88 б cмˆ4 PŽТ б Та Т5.2СpСб cмˆ4 PŽТ бУУMTP addressingЦЦ а H аб cмˆ4 PŽТ бФФС СThere is a two part addressing mechanism in the MTP, one part of the mechanism uses the point code which is incorporated in the routing label of every message signal unit, the other part of the mechanism makes use of the service indicator and network indicator within the service information octet. The point code is used for interР-Рnode addressing and the SIO addresses signalling system users on an intraР-Рnode basis. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТX  ТТX јТС€  СС€ HС5.2.1С јСб cмˆ4 PŽТ бУУPoint codesЦЦ аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бФФС СEvery signalling point (SP) and signalling transfer point (STP), when integrated in an SP, will be allocated its own unique point code. This is used by the MTP routing function to direct outgoing messages towards their destination in the network as indicated by the inclusion of the appropriate point code in the routing label. This point code is known as the destination point code (DPC). The routing label also contains the point code of the SP originating the message signal unit, therefore, the combination of this originating point code (OPC) and DPC will determine the signalling relation (i.e., the network points between which MTP Р"РUserР"Р information is exchanged). The DPC is used by the receiving SP/STP discrimination function to determine whether the message is addressed to that SP or requires to be onward routed by means of the signal transfer capability of the STP. а H аС СThe DPC will always be determined and inserted in the routing label by the level 4 MTP Р"РUserР"Р. This will also generally be the same for the OPC but it is possible that since the OPC might be constant it could be inserted by the MTP. Та ТС€ HС5.2.2С СУУService indicator and network indicatorЦЦ ФФС СThe 4 bit service indicator (SI) and 2 bit network indicator (NI) are included in the service information octet (SIO) and are used within an SP's distribution function to determine the Р"РUserР"Р the incoming message should be delivered to. а H аС СThe SI will determine the Р"РUserР"Р, e.g., TUP, SCCP, ISUP and the NI will determine which network is concerned, e.g., international or national. С СThe NI will also in conjunction with the OPC/DPC determine whether a national or international signalling relation/routing is involved. а H аС СThe NI, together with the standard 14 bit point code, allows for a max 16 384 point codes to be allocated in a signalling network. 5.3Тh  ТУУSCCP addressingЦЦ ФФС СAddressing within the SCCP of S.S. No. 7 makes use of three separate elements: Та ТР-РТ№ ТDPCЦЦ Та ТР-РТ№ ТGlobal Title (GT)ЦЦ Та ТР-РТ№ ТSubР-РSystem Number (SSN)ЦЦ а H аС СOne, two or all of the elements may be present in the Called and Calling Party Address, the main options are: б cмˆ4 PŽТ бвЦ‚HЈ ˜ ИЦв‡аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј Ј џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬа‚б cмˆ4 PŽТ бGT DPC + SSN аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH№XР( јPИџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаWhen transferring SCCP messages а ˜ И ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџ˜ №XР( јPИџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бˆа ˜ И аб cмˆ4 PŽТ бвЦ‚HЈ ˜ ИЦв‡аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџpи P Ј Ј ˜ џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бSSN GT SSN + GT аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџ˜ №XР( јPИџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬа а ˜ ` аWhen receiving messages from MTP а ˜ И аб cмˆ4 PŽТ бˆа ˜ И аб cмˆ4 PŽТ бвЦ‚HЈ ˜ ИЦв‡аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџpи P Ј Ј ˜ џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бDPC DPC + (SSN or GT or both) GT GT + SSn аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџ˜ №XР( јPИџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬа When receiving messages from connectionless or connectionР-Рorientated control for SCCP Routing. а ˜ И аб cмˆ4 PŽТ бˆа H ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаС СThe form of address used will depend on the service, application and underlying network. Та Т5.3.1Си Сб cмˆ4 PŽТ бУУGlobal Title (GT)ЦЦ а H аб cмˆ4 PŽТ бФФС СThe Global Title (GT) may comprise of dialled digits or another form of address that will not be recognized in the S.S. No. 7 network, therefore, if the associated message requires to be routed over the S.S. No. 7 network, translation is required. а H аС СTranslation of the GT will result in a DPC being produced and possibly also a new SSN and GT. A field is also included in the address indicator to identify the format of the global title. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТX  ТТX јТС€  СС€ HС5.3.2С јСб cмˆ4 PŽТ бУУDestination Point Code (DPC)ЦЦ а H ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бФФС СThe DPC in an address requires no translation and will merely determine if the message is destined for that in SP (incoming message) or requires to be routed over the S.S. No. 7 signalling network via the MTP. For outgoing messages this DPC should be inserted in the MTP routing label. On an incoming message the DPC in the MTP routing label should correspond to the DPC in the called address. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТX  ТТX јТС€  СС€ HС5.3.3С јСб cмˆ4 PŽТ бУУSubsystem Number (SSN)ЦЦ а H ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бФФС СThe SSN will identify a subsystem accessed via the SCCP within a node and may be a User Part, e.g., ISUP, SCCP management or an AE via TC. TC, however, will be invisible to the SCCP. а H аС СWhen examination of the DPC in an incoming message has determined that the message is for that SP, examination of the SSN will identify the concerned SCCP Р"РUserР"Р. The presence of an SSN without a DPC will also indicate a message which is addressed to that SP. а H аС СThe SSN field has an initial capacity of 255 codes with an extension code for future requirements. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТX  ТТX јТС€  СС€ HС5.4С   Сб cмˆ4 PŽТ бУУUser Part addressingЦЦ ТX  ТТX јТС€  СС€ HСб cмˆ4 PŽТ бФФ5.4.1С јСУУб cмˆ4 PŽТ бTelephone User Part addressingЦЦ а H ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бФФС СThe Telephone User Part is capable of handling E.164 (incorporating E.163) addresses in the calling and called party address information elements. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТX  ТТX јТС€  СС€ HС5.4.2С јСб cмˆ4 PŽТ бУУISDN User Part addressingЦЦ аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бФФС СThe ISDN User Part address structure is capable of handling E.164 addresses in the calling and called number, and reР-Рdirecting address information elements. Та ТС€ HС5.4.3С СУУSignalling connection control part addressesЦЦ ФФС СThe signalling connection control part is capable of handling E.164 (incorporating E.163), X.121, F.69, E.210, E.211, E.212, E.213, addresses, and the mobile hybrid E.214 address in the calling and called party address information elements. С СThe handling of OSI NSAP addresses in SCCP is for further study. 5.5Тh  ТУУLabellingЦЦ а H аФФС СA variety of methods to label signalling messages is used to allow the signalling system and users of the signalling system to relate a received message to a particular call or transaction. а H аС СFor circuitР-Рrelated messages, (e.g., on a simple telephone call), the TUP (and the ISUP) use the circuit identification code (CIC) to label the message. а H аС СFor certain ISUP procedures, call reference are used to associate messages with calls. С СSCCP also uses local references on connection oriented protocols. С СTransaction capabilities use transaction and invoke identities to associate transaction messages and components respectively.‚У У Та Т6СpСб cмˆ4 PŽТ бOperations administration and maintenanceЦЦ а HH аб cмˆ4 PŽТ бФ Ф6.1Тh  ТУУManagementЦЦ а Hр аФФС СManagement within S.S. No. 7 is partitioned into two main areas: Та ТР-РТ№ ТSignalling network management;ЦЦ Та ТР-РТ№ ТSignalling system management.ЦЦ а HH аТа ТС€ HС6.1.1С СУУSignalling network managementЦЦ а H аФФС СThese are functions contained within the MTP and SCCP which, by means of automatic procedures, maintain the required signalling network performance (e.g., changeover of faulty links, forced reР-Рrouting, subsystem availability, etc.). Та ТС€ HС6.1.2С СУУSignalling system managementЦЦ ФФС СThis may be considered as the actions taken by the operator (or by an external automatic mechanism) to maintain the signalling system performance when problems are identified. Та ТС€ HС6.1.3С СУУSignalling System No. 7 and TMNЦЦ а H аФФС СThe TMN concept identifies CCITT S.S. No. 7 as a candidate to act as a data communications network (DCN) for some TMN functions. The protocols that will be needed for this purpose are intended to be defined as ASEs, as part of OMAP. This topic is for further study. Та ТС€ HС6.1.4С СУУSignalling System No. 7 and OSI managementЦЦ ФФС СThis subject is for further study. 6.2Тh  ТУУMaintenance and testingЦЦ а H аФФС СThe maintenance administration and management functions of the signalling system themselves use the signalling system as a data carrying mechanism. When regarded in the data transport mode, however, any management or maintenance information is regarded as signalling traffic. Those functions having direct impact on S.S. No. 7 are included in OMAP Recommendation Q.795. С СTesting within Signalling System No. 7 is: а H аТа ТР-РТ№ Тinstigated automatically as a part of a signalling system management procedures (e.g., signalling route set test in MTP) orЦЦ а H аТа ТР-РТ№ Тapplied as a result of external activity, e.g., humanР-Рmachine (MMI).ЦЦ а HH аС СThe first form is described in the appropriate Q.700 to Q.795 Recommendation dealing with MTP or SCCP, etc. The second form includes some MMI initiated procedures (initiation of MRVT (Q.795)), and also preР-Рin service testing using test cases specified in Recommendations for S.S. No. 7 tests (Q.780 to Q.783). A testing user part has been agreed to be necessary for preР-Рin service testing, this topic is for further study. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТX  ТТX јТС€  СС€ HС6.2.1С јСб cмˆ4 PŽТ бУУOperations Maintenance and Administration Part (OMAP)ЦЦ а H№ ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бФФС СRecommendation Q.795 provides procedures and protocols related to operations and maintenance information. These procedures and protocols use TCAP and are invoked by the system management application process (SMAP). Recommendation Q.795 includes the following: Та ТР-РТ№ ТMTP Routing Verification Test (MRVT)ЦЦ Та ТР-РТ№ ТSCCP Routing Verification Test (SRVT) Р-Р for further studyЦЦ Та ТР-РТ№ ТCircuit Validation TestЦЦ а H аС СThe protocol for the MRVT contained in Q.795 forms part of the OMAP AE which in turn uses the services provided by transaction capabilities. С СASEs needed to support the TMN functions are for further study. Та Т6.2.2Си СУУTestingЦЦ а Hh аФФС СTest specifications for Signalling System No. 7 are contained in Recommendations Q.780Р-Р783 and cover MTP level 2, level 3 and the TUP together with an overview of testing. С СA Testing User Part is for further study. 6.3Тh  ТУУCCITT S.S. No. 7 measurementsЦЦ а H аФФС СRecommendation Q.791 specifies the monitoring and measurements appropriate to the MTP and SCCP. ‚У У7ТX ТSignalling system performanceФ ФЦЦ а H аС СThe performance requirements of Signalling System No. 7 must take account of the performance requirements of the services that are being supported. Each functional component of Signalling System No. 7 has its performance criteria specified in a selfР-Рcontained Recommendation. An overall performance target is specified in the form of a Hypothetical Signalling Reference Connection (HSRC). аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТX  ТТX јТС€  СС€ HС7.1С   Сб cмˆ4 PŽТ бУУHypothetical Signalling Reference Connection (HSRC)ЦЦ а H ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бФФС СThe HSRC for Signalling System No. 7 (Recommendation Q.709), identifies components that are used in a signalling relation between signalling end points, signalling points, signalling transfer points, and signalling points with SCCP relay functions, and gives the values for the signalling delays and unavailability parameters. The values used are derived from the figures contained in the individual performance Recommendations for MTP, TUP, SCCP and ISUP. 7.2Тh  ТУУMTPЦЦ ФФС СThe MTP signalling performance requirements are specified in Recommendation Q.706. This Recommendation includes: а H аТа ТР-РТ№ Тthe parameters routeР-Рset unavailability, MTP malfunction (loss of messages and misР-Рsequencing), and message transfer times;ЦЦ а Hр аТа ТР-РТ№ Тfactors affecting performance, for example signalling traffic characteristics (e.g., loading potential, security, etc.)ЦЦ а H аТа ТТ№ Тand parameters related to transmission characteristics (e.g., bit rates of signalling data links);ЦЦ а Hx аТа ТР-РТ№ Тthose parameters which have greatest influence on the signalling network queueing delays for example, error control, security arrangements, failures and priorities.ЦЦ а H аС СIt should be noted that management functions affect MTP performance. 7.3Тh  ТУУSCCPЦЦ ФФС СThe SCCP signalling performance requirements are contained in Recommendation Q.716. Parameters identified are signal connection delays (establishment, unsolicited reset, reset and release signalling connection, reset and release failure probability, data message transmit delay, data message delay failure and error probability and SCCP unavailability). С СIt should be noted that management functions affect SCCP performance. 7.4Тh  ТУУTUPЦЦ ФФС СThe TUP signalling performance requirements are contained in Recommendation Q.725. Parameters contained in this Recommendation are cross office performance for TUP supported circuit connection control application under normal and abnormal traffic loads. Also specified is the probability of failure of calls due to signalling malfunction. Та Т7.5СpСУУISDNР-РUPЦЦ а Hh аФФС СThe ISDNР-РUP signalling performance requirements are contained in Recommendation Q.766. Parameters contained in this Recommendation are cross office performance for ISDNР-РUP supported circuit connection control under normal and abnormal traffic loads. Also specified is the probability of failure of an ISDN call due to signalling function. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТX  ТТX јТС€  СС€ HС‚У У8С  Сб cмˆ4 PŽТ бFlow controlЦЦ а H ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бФ ФС СSignalling System No. 7 in common with other transport mechanisms, needs to limit the input of data when congestion onset is detected. Failure to do so can create overload situations. The nature of CCITT S.S. No. 7 will lead to SP/STP overload congestion being spread through the signalling network if no action is taken. This will result in impaired signalling performance. In addition to signalling network congestion within a node, congestion will also require action to prevent signalling performance from deteriorating. There is thus a need for flow control within the signalling system to maintain the required signalling performance. 8.1Тh  ТУУSignalling network flow controlЦЦ а H аФФС СThis is achieved by incorporating a flow control mechanism in the MTP. On detection of congestion, MTP Р"РUsersР"Р are informed by the means of a special primitive; the Р"РUserР"Р should then reduce signalling traffic towards the congested part of the network. If the User is at a remote SP, the information is carried across the network in an appropriate signalling network management message. 8.2Тh  ТУУSignalling node (congestion) flow controlЦЦ ФФС СIn addition to network congestion, nodal congestion also requires the remedial action of flow control to prevent the signalling performance from being impaired. Nodal congestion can occur both within the MTP and the MTP Р"РUserР"Р. Та ТС€ HС8.2.1С СУУMTP nodal flow controlЦЦ ФФС СA similar activity to that to combat signalling network congestion is required, i.e., on detection, the Р"РUserР"Р is informed so that traffic can be reduced. Та ТС€ HС8.2.2С СУУР"РUserР"Р flow controlЦЦ а H аФФС СAs well as taking action to reduce MTP congestion, mechanisms are also required within the User to detect the onset of congestion and to take appropriate action. 8.3Тh  ТУУAutomatic congestion controlЦЦ а H аФФС СThe ISUP and TUP provide signalling procedures which aim to reduce the new calls offered to an exchange which is experiencing processor overload. С СAutomatic congestion control provides the means to inform adjacent exchanges of the current workload, and to request that only priority calls are offered to the exchange experiencing overload. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТX  ТТX јТС€  СС€ HС‚У У9С  Сб cмˆ4 PŽТ бCompatibility mechanisms and rules in CCITT S.S. No. 7ЦЦ аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бФ Ф9.1Тh  ТУУModularityЦЦ а H аФФС СThe wide scope of the signalling system requires that the total system include a large diversity of functions and that further functions can be added to cater for extended future applications. As a consequence only a subset of the total system may need to be used in an individual application. а H аС СA major characteristic of the signalling system is that it is specified with a functional structure to ensure flexibility and modularity for а H аdiverse applications within one system concept. This allows the system to be realized as a number of functional modules which could ease adaptation of the functional content of an operating Signalling System No. 7 to the requirements of its application. а H аС СThe CCITT specifications of the signalling system specify functions and their use for international operation of the system. Many of those functions are also required in typical national applications. Furthermore, the system to some extent includes features that are particular to national applications. The CCITT specifications thus form an internationally standardized base for a wide range of national applications of common channel signalling. а H аС СCCITT S.S. No. 7 is one common channel signalling system. However, as a consequence of its modularity and its intended use as a standard base for national applications the system may be applied in many forms. In general, to define the use of the system in a given national application, a selection of the CCITT specified functions must be made and the necessary additional national functions must be specified depending on the nature of the application. а H аС СCCITT S.S. No. 7 is an evolutionary signalling system which has undergone a number of enhancements. To allow ease of evolution it has been necessary to incorporate a number of compatibility mechanisms in various functional elements of CCITT No. 7, and to apply a number of compatibility rules to protocol enhancement. Detailed specification of the compatibility mechanisms in each functional element of CCITT S.S. No. 7 are given in the appropriate Q.700 to Q.795 Recommendations. Hence an overview is given in this Recommendation. а H аС СCompatibility rules which apply to all functional elements of CCITT S.S. No. 7 are detailed in the following text. 9.2Тh  ТУУEvolutionary requirementsЦЦ ФФС СIn application protocols (e.g., ISDNР-РUP, ASEs), the main evolutionary requirement is the ability to add new subscriber services, new administration and network services to the protocol. а H аС СIn the SCCP and MTP, the evolutionary requirements are different in that initial versions provide basic transport functions which are generally stable. The main enhancements have been in the management protocols. а H аС СAlthough the evolutionary requirements are different across the elements of CCITT S.S. No. 7, it is possible to incorporate certain common mechanisms in the various functional elements. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТX  ТТX јТС€  СС€ HС9.3С   Сб cмˆ4 PŽТ бУУForward and backward compatibilityЦЦ аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бФФС СCompatibility mechanisms can be considered as being either: Та ТР-РТ№ ТForward compatibility mechanismsЦЦ Та ТР-РТ№ ТBackward compatibility rulesЦЦ а H аС СForward compatibility mechanisms are defined as a scheme to enable a version of a protocol to communicate effectively and interwork with future versions of the protocol. а H аС СBackward compatibility rules are defined as a scheme to ensure that future versions of the protocol will be able to send protocol messages to the previous version which will be understood and fully processed by the node supporting the previous version. 9.4Тh  ТУУCompatibility rules for CCITT S.S. No. 7ЦЦ а H аФФС СThe following compatibility rules are applied to each element of CCITT S.S. No. 7 (e.g., ISDNР-РUP) when protocols are enhanced. Та ТС€ HС9.4.1С СУУAddition of a new value to an existing field (e.g., a cause value)ЦЦ а H аФФС СNew values to an existing field can be added. The processing of these new values at nodes supporting an earlier version of the protocol will be defined in their version specifications. Та ТС€ HС9.4.2С СУУAddition of a new parameter to an existing messageЦЦ ФФС СAny new parameters added to an existing message must not be added as mandatory parameters. If a new parameter, must be added, and it must be a mandatory parameter, then a new message type must be created. Та ТС€ HС9.4.3С СУУHandling of unrecognized informationЦЦ а H аФФС СWhen a new protocol, message or information element is created, a rule is required on a per message and information element basis, to define the action on receipt of unrecognized information. This rule needs to be applied to both unrecognized messages, unrecognized information elements within messages, and unrecognized values within recognized information elements. а H аС СThe actions defined for receipt of an unrecognized message/information element could be: Та ТР-РТ№ ТDiscard message/information element.ЦЦ а Hh аТа ТР-РТ№ ТDiscard/ignore information element within a recognized message.ЦЦ а H аТа ТР-РТ№ ТDefault to a known general value (e.g., on receipt of an ISDNР-РUP IAM with an unrecognized calling party category could be defaulted to Р"РUnknownР"Р).ЦЦ Та ТР-РТ№ ТSend a Р"РConfusionР"Р message.ЦЦ Та ТР-РТ№ ТTerminate the call/transaction.ЦЦ Та ТР-РТ№ ТInformation management.ЦЦ а HH аТа ТС€ HС9.4.4С СУУIncrease in the length of optional parametersЦЦ а H аФФС СIf a parameter is used as an optional parameter in all messages that it appears, the length of the parameter can be increased. The older version of the protocol would be able to function as it does today, assuming it ignores the extra bits or a suitable extension method has been defined. The newer version would have to check the length of the parameter to determine if the added information was present. а H аС СProtocols which use coding rules which are based on X.409 (e.g., TC) are not subject to this rule. Та ТС€ HС9.4.5С СУУProcessing of messages with unrecognized SIO informationЦЦ а H аФФС СTo enable signalling points implemented to the Blue Book to interwork with signalling points implemented to earlier Recommendations when a message containing an unrecognized service information octet (see Q.704, РSР 14.2) is received, the message is discarded. Та ТС€ HС9.4.6С СУУUnacknowledged messagesЦЦ ФФС СWhere a function requires an acknowledgement to a message in order to continue, if no response is received the function sends the message for only а H аa limited number of times. The sending signalling point should assume that the function is not available, and inform local management. Та ТС€ HС9.4.7С СУУProcessing of spare fieldsЦЦ а H аФФС СFor those CCITT S.S. No. 7 functions which define fields or subР-Рfields in signalling messages as spare or reserved, the following rules for processing of these fields apply. а H аС СAt a node generating a signalling message, all spare and reserved fields are set to zero. At transit nodes, spare or reserved fields may be passed а H аon transparently. At the destination node, the spare and reserved fields are not examined. ‚У У10Тр  ТGlossaryФ ФЦЦ а H аС СA Glossary of terms in CCITT S.S. No. 7 is contained at the back of the Fascicles VI.7, VI.8 and VI.9.