1、CEPT T/N*23-02*E 2326414 0006073 L = T/N 23-02 E Page 1 Recommendation T/N 23-02 (by correspondence April 1987, revised in Edinburgh 1988) ROUTING IN THE ISDN, FOR GAP PHASE 1 SERVICES Recommendation proposed by Working Group T/WG 14 “Network aspects” (NA) Text of the revised Recommendation adopted
2、by the “Telecommunications” Commission. “The European Conference of Postal and Telecommunications Administrations, considering - that the interconnection of ISDNs in Europe is an important requirement for European Administrations (see GAP - that there is a need to complement existing CEPT and CCITT
3、texts on call routing in the ISDN, recommends that European Administrations, who wish to interconnect ISDNs, apply the following Recommendations.” report of the EEC), 1. 2. 2.1. 2.2. 2.3. 2.4. 3. 4. 4.1. 4.2. 5. 5.1. 5.2. 6. 6.1. 6.2. 6.3. Contents INTRODUCTION . . . . . . . . . . . . . . . . . . .
4、. . . . . . . . . . . . . . . . RESOURCES PROVIDED BY THE NETWORK . . . . . . . . . . . . . . . . . . . . . Service and network aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Scope of the document. . . . . . . . . . . . . . . . . . . . . . . , , . , . . . . . . . Signalling ca
5、pabilities . . . . . . . . . . . . . . . . . . . . , , . . , . . . . . . . . . Network resource concept . . . . . . . . . . . . . . , . , . . . . . . . . . . . . . . . RELATIONSHIP BETWEEN INFORMATION TRANSFER CAPABILITIES AND BASIC CONNECTION COMPONENTS . . . . , . . , . . . . . . . . . . . . . . .
6、 . . . . . INFORMATION USED BY ROUTING FUNCTIONS IN THE INTERNATIONAL NETWORK General Values of network resources , , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ROUTING PROCEDURES IN AN INTERNATIONAL EXCHANGE . . . . . . . . . . . . Concerning the information transfer capabilities . .
7、 . . . . . . . . . . . . . . . . . . . . . Concerning the signalling capabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . ROUTING OF AN INTERNATIONAL CALL . . . . . . . . . . . . . . . . . . . . . . Notations . Telephone service . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8、 . . . . . . . 64 kbit/s services (e.g. facsimile, Teletex .) . . . . . . . . . . , . . . . . . . . . . . . . . 5 6 6 6 6 6 6 7 8 8 9 Annex 1. Various routing configurations (extract of Recommendation 1.3) i . . . . . . . . . . 11 Annex 2. Relationship between services and network resources . . . .
9、. . . . . . . . . . . . . 12 Annex 3. Relationship between some concepts defined in Recommendations 1.340 2, 1.32 3 and 1.34 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Annex 4. Documents of interest for routing questions . . . . . . . . . . . . . . . . . . . . . 1
10、6 ) Replaces Recommendation T/S 26-01. Edition of February 28, 1989 I CEPT T/N*23-02*E 232b414 0006074 3 T/N 23-02 E Page 2 I 1. INTRODUCTION I 2. RESOURCES PROVIDED BY THE NETWORK This document contains specifications related to routing applicable to the ISDN interconnection for services identified
11、 by the GAP, for introduction in the first phase of ISDN in Europe. Its purpose is to complement work already done in CEPT and CCITT about call routing in the ISDN: - CEPT Recommendation T/GSI 03-06 5, ISDN routing principles; - CCITT Draft Recommendations: - 1.3 i, ISDN routing principles, - E.172
12、6, Call routing in the ISDN era, For the time being, 1.3 i and E.172 6 field of application is primarily ISDN so that it does not fully take into account aspects such as: - service interworking between ISDN and analogue subscribers - existence of different signalling capabilities in the network: CCI
13、TT No. 7 User Parts, enhanced TUP Furthermore full definition of teleservices and supplementary services is not yet available from CCITT. 1.3 i and E.172 6 are not yet stable Recommendations. Therefore, it is not considered that they are a part of this Recommendation, but they give the background of
14、 studies on routing in CCITT. A list of CEPT or CCITT documents of interest for routing questions appears as Annex 4. (TUP +), channel associated signalling systems, etc. 2.1. Service and network aspects Preliminary note. The following considerations only result from principles already defined in wo
15、rking draft revision of Recommendation 1.340 2 (Connection types), 1.3 i and E.172 6. For each occasion a service is invoked by a user, the network has to provide an ISDN connection of a given type. This ISDN connection involves switching and transmission means, and signalling systems or proto- cols
16、. The selection of appropriate ISDN connection is part of the routing functions. An ISDN connection has a meaning between ISDN reference points, e.g. between two S/T reference points. ISDN connection types are characterized by a set of attributes, each attribute having a set of admissible values, an
17、d are defined in CCITT Recommendation 1.340 2. 2.1.1. ISDN connection types 2.1.2. Connection elements An ISDN connection type is made up of connection elements. The following kinds of connection elements may compose a connection type: - access connection element - national transit connection elemen
18、t - international transit connection element Each kind of connection element is also characterized by a set of attributes. The attribute values of a connection type will depend on the attribute values of the related attributes of different connection elements composing the connection type. 2.1.3. Ba
19、sic connection components A connection element is composed of basic connection components. A basic connection component corresponds to some switching/transmission/signalling (physical) means. The relationship between these different entities defined in Recommendations 1.340 2, 1.32 3 and 1.34 4 and
20、useful in the routing context is shown in Annex 3 (for more information, refer to these Recommenda- tions). 2.1.4. Edition of February 28, 1989 CEPT T/N*23-02*E m 232b4L4 000b075 5 m + T/N 23-02 E Page 3 Basic connection components 2.2. Scope of the document Routing configurations for various applic
21、ations are shown in the Annex 1 of this document, which reproduces the Annex 1 of Draft Recommendation 1.3 I. For the services involved in this document, it is possible to make the following limitations: - the routing functions are mainly concerned with the transit (national and international) conne
22、ction element, i.e. the part of the connection (type) between the originating and destination local exchanges; - since this document specifies routing in the international network, only the provision of an appropriate international transit connection element will be considered; - only the following
23、two attributes of the international transit connection element are of interest for routing purpose: - the INFORMATION TRANSFER CAPABILITY (ITC) of the international transit connection element (called in the present draft version of 1.340 2, see Annex 4: information transfer susceptance) which is rel
24、ated to the transmission and switching capability of the network; - the SIGNALLING CAPABILITY (SC) of the international transit connection element (called in the present draft version of 1.340 2: Connection Control Protocol), which is related to the signalling system to be adopted for controlling th
25、e various phases of a call. The Signalling Capability has a strong relationship with the Supplementary Service Resource Requirement - SRR - as defined in Draft Recommendation E.172 6. This is for further study. Note 1. Other attributes may need to be examined to support the international routing of
26、the 64 kbit/s packet mode bearer service. This is for further study. Note 2. Quality of service and network performance will also have impact on the call routing. However, in the short term, this aspect is not taken into consideration, since the customer cannot have any influence on the QOS. Adminis
27、trations should nevertheless take care of it when planning their routing arrangements. Note 3. The interworking between ISDN and PDN has no impact on routing in the international network, in the short term. The results of this approach is to provide a mapping between the services and the ISDN connec
28、tion types, then a mapping between the ISDN connection types and the transit connection elements, but considering only the two attributes identified above. Finally, the results can be directly presented as a mapping between the services and the values of the capability attributes (information transf
29、er and signalling) of the transit connection element necessary to provide each service. This relationship between a requested service and the corresponding information transfer capability and signalling capability of the international transit connection element is defined in Annex 2. This approach i
30、s illustrated by the Figure below: + connection (-ITC Transit connection element =b Information transfer capability I I 1 I Signalling capability Signalling systems Edition of February 28, 1989 I CEPT T/N*23-02*E 2326434 000b07b 7 M T/N 23-02 E Page 4 2.3. Signalling capabilities Since the telephone
31、 network should progressively evolve towards ISDN, not all parts of the network will have at the beginning the same signalling capabilities. Between two given exchanges in the network, the following signalling systems may for example be available: - channel associated signalling: R2, . - CCITT No. 7
32、 signalling: Red Book TUP - CCITT No. 7 signalling: enhanced TUP (TUP+), ISUP Because of the different signalling capabilities of the various signalling systems, in term of services each one can support, the routing functions have to take into account the signalling capabilities of the network, to e
33、nsure correct provision of the requested service. Furthermore, it is also necessary to consider the case where the required service can be provided, but with some restrictions. For example, for a telephone call between two ISDN subscribers, Red Book TUP may be sufficient to set up a basic call but d
34、oes not allow certain end to end information transfer (e.g. user to user signalling) and some other supplementary services. The routing principles shall consider these different cases, depending on service requirements and available signalling capabilities. 2.4. Network resource concept Bearer servi
35、ces and teleservices are offered on the access. With regard to the network, for each service requested by a user, the network has finally to provide a network resource of a given type. A network resource is defined by two types of network capabilities: - information transfer capability - signalling
36、capability The network resource concept is introduced for the routing needs, as an aid to determine the appropriate network components to fulfil the service requirement. This concept is illustrated by the figure below: =Is=; p2-l =-;= pl requested provided The network resource concept has a strong r
37、elationship with the network capabilities, as used in Recommen- dation 1.310 7 and with the connection type (see paragraph 2.2.). The relationship (1) between a requested service and the network resource which is required for routing purpose is defined in Annex 2. The relationship (2) is defined in
38、the following parts of this document: -in paragraph 3. are identified the basic connection components that can be used to satisfy each - in paragraph 5.2. are identified the signalling systems that can be used to provide each signalling Only those aspects of the network resource which have to be pro
39、vided between the originating and the destination exchanges are considered in this document. The GAP Phase 1 services do not have any impact on routing in the access connection element. The network resource may be made available via several networks, each network having to provide the appropriate pa
40、rt of the overall network resource. The routing functions in each exchange have thus to select an outgoing route which is appropriate for the provision of the overall network resource. The above principles about network resources involving several networks are quite similar to those concerning conne
41、ction defined in Recommendation 1.340 2, paragraph 2.5. information transfer capability; capability and information transfer capability. Edition of February 28, 19R9 CEPT T/N*23-02*E 232b414 0006077 i Transmission TIN 23-02 E Page 5 Switching 3. RELATIONSHIP BETWEEN INFORMATION TRANSFER CAPABILITIES
42、 AND BASIC CONNEC- TION COMPONENTS This relationship is defined for the information transfer capabilities (ITC) identified in paragraph 4.2. by content of Table 1 (T/N 23-02), based on Table 4 of Recommendation E.172 6. The table shows only the technical feasibility for the support of connection ele
43、ments by basic connection components, and it should not be considered mandatory for the provision of all the basic connection components. The choice of basic connection components needs further consideration when planning the interconnection. Notes. (a) Both analogue and digital circuits may be used
44、 to provide the ITC “speech”. The choice between both is a question (b) Table 1 (T/N 23-02) shows that a given “terrestrial” circuit may be used to realize connections of different types: concerning the planning and the implementation of the network and is a national matter. - an analogue circuit al
45、lows: speech, 3.1 kHz audio - a digital circuit allows: 64 kbit/s unrestricted, speech, 3.1 kHz audio The above considerations are service independent. Information transfer capability 64 kbit/s unrestricted Speech 3.1 kHz audio I Note 3 Note 4 - - 2 .CI $lo fJ 0 3- - so -0 M* $3 cds e0.S 2 C 3 o=: .
46、-=: o 0 .e 0 3 ,503 .- g- o OM cp .$o .ao - a-& ar4 m 22 ci2 4 O 85 ADPCM 32 kb 16 kb $ V V V - - - - - - - Note I Note 5 V V V V V V V V Note 6 Note 6 V V V V V V V V V V V V V V V V Note 8 Note 7 Note 7 Note 2 Note 6 Note 6 Table 1 (T/N 23-02). Some examples of basic connection components which co
47、nstitute, or could occur in, connection elements. Note I. Provided the transmission line code is bit sequence independent. Otherwise only 64 kbit/s restricted is possible. Note 2. DSI could be included in a connection element selected for a voice-band data call. However, the constant activity of voi
48、ce-band data would cause permanent trunk/channel assignment for the duration of the call, thereby reducing the potential DSI gain. Note 3. Currently only 32 kbit/s ADPCM in accordance with G.721 8. Note 4. For the number of links in the total connection see paragraph 3. of Recommendation E.172 6, an
49、d for satellite links see Notes 5 and 6. Nore 5. Refer to Recommendation X.110 9 for the requirements on the number of satellite links in PDN. Extract of Recommendation X.110 9: “In accordance with Recommendation X.92 IO, no more than three satellite links should normally be included in an overall PDN route. The international network part should normally not include more than two satellite links.” Note 6. Refer to Recommendation E.171 I 11 for the requirements on the number of satellite links in PSTN. Extr
