1、- CEPT T/GSI*03-0bq E 85 2326414 0005572 i ! Recommendation T/GCi 03-06 (Nice 1985) concerning Routing T/GSI 03-06 E Page 1 i Recommendation proposed by the Special Group Intergration (GSI) Text of the Recommendation adopted by the “Telecommunications” Commission: “The European Conference of Posts a
2、nd Telecommunications Administrations, Considering - the common CEPT approach to the ISDN and general CEPT assumptions and policies for the evolution towards ISDN; - the I. Series Recommendations of the CCITT, as well as other CCITT Recommendations on ISDN, to which - the need for CEPT Administratio
3、ns to have more precise answers to their specific European requirements, i,e. - the need for CEPT Administrations to have as a base a comprehensive set of Recommendations, in order to CEPT Administrations have contributed most significantly; to select and further dene material from CCITT Recommendat
4、ions; promote and strengthen European harmonisation. Recommends - to the member Administrations of the CEPT, that they evolve their telecommunication network towards ISDN O according to the guidelines and specifications given in the attached text.” Edition of September 15, 1985 CEPT T/GSI*03-Ob E 85
5、 232bYL4 0005593 O E Time Independent T/GSI 03-06 E Page3 . Rodting Principles Telecommunication ISDN Connection Type Service -+ (ISDN Connection Element) ISDN ROUTING PRINCIPLES 1. GENERAL, Inst ance Rkte The objective of this recommendation is to set up principles for routing communicaLms between
6、ISDN users and between ISDN users and non ISDN networks. It also describes the general relationship between Telecommunication Services and ISDN connection types. Taking into account the recommendations: - describing ISDN services, - describing ISDN connection types, - giving principles of addressing
7、 in ISDN, - defining an ISDN architectural model, Considering also that interworking between different telecommunication services and the impact of charging and tarifs on routing are for further study, this recommendation sets principles for routing a call with respect to the following connection co
8、nfigurations: - S/T to an internetwork interface - S/T to an HLF - Internetwork interface to another internetwork interface. - E.170, E.171, X.110. - S/T to S/T 2. RELATIONSHIP BETWEEN TELECOMMUNICATION SERVICES AND ISDN NETWORK CAPA- BILITIES As described in 1.210 Telecommunication Services are the
9、 communication capabilities offered to customers. The service concept can therefore be considered to be time independent. A particular instance (or use by the user) of a service is commonly refered to as a “call”. Likewise the network capabilities which support services, the ISDN connection types ar
10、e described in 1.340. These connection types are also time independent in their concept. A particular instance (or use by the network) of a connection type is a connection. The concept is ilistrated in Figure 1. I SERVICE I NETWORK Figure 1. Diagram of relationships of service and network aspects in
11、 ISDN. Note: The use of “call” as a service oriented concept in this Recommendation does not preclude the use of %all” as a network oriented concept in other studies. As can be seen from this figure the general relationship between services and ISDN connection types should be considered as the routi
12、ng principle for the ISDN. A particular application of the routing principles is a “route” which is considered to be the relationship between a call and a connection. From the users point of view it is the call that is being routed. From the networks point of view it is the connection that is being
13、routed. The generation of a routing plan, based on these principles, will describe the specific relationship between a particular service and one or more connection types. Appendix 1 gives some preliminary draft proposals for this routing plan. 3. PRINCIPLES TO ESTABLISH A CALL THROUGH ISDN Proper i
14、nternational communications management needs the defnition of a common set of general rules to be followed everywhere. In order to establish a call, an ISDN must select: - the appropriate functional groups needs to support the service; - the appropriate association between the selected functional gr
15、oup. r Edition of September 15, 1985 T _ _ I 1 CEPT T/GSI*03-06 E 5 W 23261iL4 0005591i 2 W T/GSI 03-06 E Page 4 The appropriate functional groups is selected on the basis of the information in the service request. This information has to be passed to every switching node of an ISDN as well as to th
16、e called user in the form of the description of the connection type selected by the network. Quality of service indications forming part of the bearer capability information may be used for routing purposes, for instance avoiding a satellite hop in order to fulfill a signal transfer delay requiremen
17、t. The appropriate route, that is the connection for a particular call, is selected on the basis of the called subscriber number. This number is either an ISDN number or a prefix followed by a number in a non ISDN numbering plan (e.g. X.121). 4. VARIOUS ROUTING CONFIGURATIONS Special Nodes and Centr
18、es Customers Network Access CE I tl National (and International) Transit CE Figure 2. Examples of routing a connection within ISDN Dedicated Networks Operators Operation and Maintenance Staff Figure 2 shows various ways of routing connections in an ISDN and where various functions are performed. The
19、 connections in an ISDN are marked with the numbers 1 to 8 as follows: O O O 6) O * Other combinations of access and transit connection elements may be involved in these routings. Also calls related in ISDN services may be routed through dedicated networks used to carry specialised trafic or interwo
20、rking with non ISDN subscriber. The range of permissible routings of calls encountering one or more transitions between an ISDN and dedicated networks depends on several factors including, the quality of service constraints and HRX agreements. Figure 3 defines the range of mixed ISDN to dedicated ne
21、twork routing. As an objective the panber of . transitions between networks should be minimised. Local connection between customers (Le. utilising only the access connection element). Transit connection between customers (Le. involving the national (and international) connection element as well as a
22、ccess). Connection between a customer and a node for special services. Connection between customers via a node for special services*. Connection between customers in the ISDN and customers in dedicated networks“. Connection between a customer and an operator*. Connection between customers via an ope
23、rator *. Test connection from an operations and maintenance centre to test a customers access. _ - Edition of September 15, 1985 CEPT T/GSI*03-Ob E 85 232b414 0005595 4 5. 5.1. 5.2. 5.3. 6. 6.1. 6.2. T/GSI 03-06 E Page 5 USE OF USER PROVIDED INFORMATION FOR THE PURPOSE OF ROUTING A CALL Use of sub a
24、ddressing information The possibillity of an ISDN having information on the subscriber installation beyond reference point T is a national option. CCITT recommended routing principles are based on ISDN not memorising or proces- sing any information relating to the subscriber installation, Therefore
25、subaddress information has to be passed from user to user without being processed by ISDN for routing purposes. Use of user to user information on low layer compatibility Such information has to be passed from user to user but should not be used for international routing of ISDN calls. They could ho
26、wever be used in some national .networks, depending on national implementations. Use of user to user information on high layer compatibility This information has to be passed through the ISDN from user to user. In the simplest case, where only low layer functions are involved in ISDN, this informati
27、on should not be process for routing purposes. In the case of network provided interworking the use of high layer compatibility information for routing purposes must be studied. For international communications where in a given country a teleservice is not supported by one of the connection types re
28、commended by CCITT then interworking recommendations will specify the procedure to be adopted. RPOA INDICATTON AND SELECTION When authorised by national regulation, a national ISDN should be able to route a call to another national ISDN, as required by the calling user request or the called user loc
29、ation. Indication of the destination RPOA For connections from one country where RPOA indication is not applied to another country where RPOA indication is applied, RPOA indication is either not processed or processed as part of the trunk indication, i.e. Network Destination Code, by the originating
30、 network. Further studies are required to determine the maximum number of digits to be processed by the originating network. RPOA selection for transit trafic RPOA selection is a national option not recommended by CCITT to be applied in every country. The method to indicate the selected RPOA should
31、not be mandatory. I ! Edition of September IS, 1985 7 1 l CEPT T/GSI*03-06 E 85 I 2326434 000559b b T/GSI 03-06 E Page 6 R 0s TE2 -TA- i 1 ISDN 7 S R I TA TE2 - Existing Dedicated Network R- s , I TE2 TA R S I I . TA TE2 R S TE2 TA I I I w S R I I TA TE2 s- RL I TA 1 TE2 S I TE 1 Figure 3. Mixed ISD
32、N to dedicated network routings. Edition of September 15, 1985 Q 64 kbitls. Speech 3.1 kHz Unres. Audio Bearer Services CEPT T/GSI*03-06 E 85 m 2326414 0005597 8 m,! - 384 kbitls. 1920 kbitls. Unres. Unres. T/GSI 03-06 E Page 7 Speech 3.1 kHz Audio Speechmon Speech Speech/3.1 kHz Audio Appendix 1 1
33、2 3 1 I J 2 2 J3 J“ 2 2&3 Routing Plan 384 kbitls. Unrestricted 1920 kbitls. Unrestrited The table below indicates a possible relationship between ISDN Beaser Services and Connection Types (circuit mode) *. I I I J J I I I I J I Connection Types I I l l I I I 64 kbit/s. Unrestricted I ,I I /I II Edition of September 15, 1985
