1、CEPT T/S*Zb-Ol*E 7 W 2326414 0007780 b W- 26-01 Page E 1 Recommendation T/S 26-01 (by correspondence, April 1987) ROUTING IN THE ISDN, FOR GAP PHASE 1 SERVICES Recommendation proposed by Working Group T/WG 1 1 “Signalling, Protocols aad Switching” (SPS) Text of the revised Recommendation adopted by
2、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 tex
3、ts on call routing in the ISDN, recommends that European Administrations, who wish to interconnect ISDNs, apply the following Recommendations.” report of the EEC), Q 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 : . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Scopeofthedocument. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , . Signalling capabilitie
5、s . . . . , . . . . . . . . . . . . . . . . . , . . . . . . . . . , , Network resource concept . , . . , . . . . . . . . , . , . . . . . . , . . . . . . . . RELATIONSHIP BETWEEN INFORMATION TRANSFER CAPABILITIES AND BASIC CONNECTION COMPONENTS . . . . . . . . . . , . . . . . . . . . . . . . . . INFO
6、RMATION 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 cafabilities . , . . . . . I . . . . . . . . . . . . . . . . . . . ROUTING OF AN INTERNATIONAL CALL . . . . . . . . . . . . , . . . . . . . . Notations . Telephone service . . . . . . . . . . . . . . . . . . . . . . . . . . . , . . . . . . . . 64
8、 kbit/s services (e.g. facsimile, Teletex .) . . . . . . . . . . . . . . . . . . . . . . . , . Annex 1. Various routing configurations (extract of Recommendation 1.3) i . . . . . . . . . . Annex 2. Relationship between services and network resources . . . . . . . . . . . , . . . , . Annex 3. Relatio
9、nship between some concepts defined in Recommendations, 1.340 2, 1.32 3 and 1.34 4 . . . . . . . . . . . . . . . . . . . , . . . . . . . , . . . , . . . . . Annex 4. Documents of interest for routing questions . . . . . . . . . . , . . . . . . . . . . 2 2 2 3 4 4 5 6 6 6 6 6 6 7 8 8 9 11 12 15 16 Ed
10、ition of August 15, 1987 . - CEPT T/S*Zb-Ol*E 87 2326434 0007983 T/S 26-01 E Page 2 1. INTRODUCTION This document contains specifications related to routing applicable to the ISDN interconnection for services identified by the GAP, for introduction in the first phase of ISDN in Europe. Its purpose i
11、s to complement work already done in CEPT and CCITT about call routing in the ISDN: - CEPT Recommendation T/N 03-06 5, ISDN routing principles; - CCITT Draft Recommendations: - 1.3 l, ISDN routing principles, SG XVIII/WP2, Geneva, July 1986 - E. 172 6, Call routing in the ISDN era, SG IIIwp3, Geneva
12、, September 1986. For the time being, I.3yy 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: CCITT No. 7 User
13、 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 studies on r
14、outing 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. RESOURCES PROVIDED BY THE NETWORK 2.1. Service and network aspects Prelitninary note. The following considerations only result from princip
15、les already defined in working draft revision of Recommendation 1.340 2 (Connection types), Geneva, July 1986 and Draft Recommendations 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 s
16、witching and transmission means, and signalling systems or proto- cols. 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 s
17、et of attributes, each attribute having a set of admissible values, and 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
18、type: - access connection element - national transit connection element - 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
19、different connection elements composing the connection type. 2.1.3. Basic 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 differe
20、nt entities defined in Recommendations 1.340 2, 1.32 3 and 1.34 4 and useful in the routing context is shown in Annex 3 (For more information, refer to these Recommenda- tions). 2.1,4. Edition of August 15, 1987 2.2. - CEPT T/S*26-01*E 87 2326434 0007982 T TIS 26-01 E Page 3 Scope of the document Ro
21、uting congurations for various applications 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 trans
22、it (national and international) connection 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
23、 be considered; - only the following 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: informati
24、on transfer susceptance) which is related 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 sy
25、stem to be adopted for controlling the various phases of a call. The Signalling Capability has a strong relationship with the Supplementary Service Resource Requirement - SRR - as dened in Draft Recommendation E.172 q. This is for further study. Note 1. Other attributes may need to be examined to su
26、pport the international routing of 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 thecall routing. However, in the short term, this aspect is not taken into consideration, since the customer cannot have
27、 any influence on the QOS. Administrations 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 betwee
28、n the services and the ISDN connection 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 capabil
29、ity attributes (information transfer 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 d
30、efined in Annex 2. This approach is illustrated by the Figure below: rlF-1 I) El + pZ-1 element + (-ITC -m (-SC . I I T. (- ITC (-SC Information connection capability components I 1 I d Signalling Signalling capability I I I I Edition of August 15, 1987 7 CEPT T/S*Zb-OL*E 7 2326434 0007783 1 M T/S 2
31、6-01 E Page 4 2.3. Signalling capabilities Since the telephone 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 a
32、vailable: - channel associated signalling: R2, . - CCIT No. 7 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
33、into account the signalling capabilities of the network, to ensure 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
34、, Red Book TUP may be sufficient to set up a basic call but does 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 signal
35、ling capabilities. 2.4. Network resource concept Bearer services and teleservices are offered on the access. With regard to the network, for each service requested by a user, the network has fnally to provide a network resource of a given type. A network resource is defined by two types of network c
36、apabilities: - information transfer capability - signalling 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: I Service request - -
37、 - - - -_-_ - components (1) requested provided The network resource concept has a strong relationship 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
38、 is required for routing purpose is defined in Annex 2. The relationship (2) is defined in 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
39、 to provide each signalling Only those aspects of the network resource which have to be provided 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 ma
40、y be made available via several networks, each network having to provide the appropriate part 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 abo
41、ut network resources involving several networks are quite similar to those concerning connection defined in Recommendation 1.340 2, paragraph 2.5. information transfer capability; capability and information transfer capability. Edition of August 15, 1987 CEPT T/S*Zh-OL*E 87 2326434 0007984 3 m I TIS
42、 26-01 E Page 5 3. RELATIONSHIP BETWEEN INFORMATION TRANSFER CAPABILITIES AND BASIC CONNEC- TION COMPONENTS This relationship is dened for the information transfer capabilities (ITC) identified in paragraph 4.2. by content of Table 1 (T/S 26-01), based on Table 4 of Recommendation E.172 a. The table
43、 shows only the technical feasibility for the support of connection elements 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 int
44、erconnection. Notes. (a) Both analogue and digital circuits may be used to provide the ITC “speech”. The choice between both is a question (b) The ITC “3.1 kHz audio” is defined to avoid equipments like ADPCM. (c) Table 1 (T/S 26-01) shows that a given “terrestrial” circuit may be used to realize co
45、nnections of different types: concerning the planning and the implementation of the network and is a national matter. - an analogue circuit allows: speech, 3.1 kHz audio - a digital circuit allows: 64 kbit/s unrestricted, speech, 3.1 kHz audio The above considerations are service independent. Basic
46、connection components Transmission Switching Information transfer capability 64 kbit/s unrestricted Speech 3.1 kHz audio V V V V Table 1 (T/S 26-01). Some examples of basic connection components which constitute, or could occur in, connection elements. Note 1. Provided the transmission line code is
47、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 voice-band data would cause permanent tmnk/channel assignment for the duration of the call, thereby
48、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, and for satellite links see Notes 5 and 6. Note 5. Refer to Recommendation X.110 9 for the requireme
49、nts on the number of satellite links in PDN. Extract of Recommendation X.110 9: “In accordance with Recommendation X.92 lo, 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 il for the requirements on the number of satellite links in PSTN. Extract of E.171 i i: “The inclusion of two or more satellite circuits in the same co
