1、CEPT T/GSI*03-05 E = 2326414 0005579 b . O3-O5 Page 1 E Recommendation T/GSI 03-05 (Nice 1985, revised by correspondence, June 1987) REFERENCE CONFIGURATIONS FOR ISDN CONNECTION TYPES Recommendation proposed by the Special Group Integration (GSI) Revised text of the Recommendation adopted by the “Te
2、lecommunications Commission: “The European Conference of Posts and 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 Rec
3、ommendations on ISDN, to which - the need for CEPT Administrations 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 significa
4、ntly, to select and further define material from CCITT Recommendations, promote and strengthen European harmonisation, O recommends to the member Administrations of the CEPT that they evolve their telecommunication networks towards ISDN according to the guidelines and specifications given in the att
5、ached text.” Edition of October 31, 1987 CEPT T/GSI*03-05 E 232b4L4 0005580 2 J T/GSI 03-05 E Page 2 1. 1.1. 1.2. 1.2.1. 1.2.2. 1.2.3. 2. 2.1. 2.2. GENERAL Basic objective of reference configurations for ISDN connection types The ISDN has a number of levels of description starting with the definitio
6、n of the ISDN, then the ISDN network functional principles (as given in Recommendation T/GSI 03-01), through the architectural model (as given in Recommendation T/GSI 03-03) to the concept of ISDN connection types as given in Recom- mendation T/GSI 03-04. That Recommendation defines and describes so
7、me ISDN Connection Types. However, it does not say what topological form they take. In order to allocate network performance parameters it is necessary to have a reference model over which the parameters can apply and which also allows a mechanism for allowing allocations of sub-divisions of the val
8、ue of a parameter to be made between different sections of an ISDN connection. This reference model is called a Connection Type Reference Configuration (hereafter simply called a reference configuration). In order to keep the task of developing reference configurations, and the allocation of perform
9、ance values to them, to manageable proportions it is necessary to have as limited a set as possible of specific reference configurations. Consequently the ISDN connection types in Recommendation T/GSI 03-04 need to be arranged in different classes which differ significantly from each other such that
10、 they require a separate reference configuration model. Existing developments The concept of reference configurations has already been used in a number of areas of standardisation of the ISDN. It is therefore necessary to see the concept of connection type reference configurations in the context of
11、these developments. ISDN Architectural Model Recommendation T/GSI 03-03 has defined generalised reference configurations and has described the concept of connection elements, both of which are generically applicable to all connection types. The concepts in this present Recommendation can be seen as
12、detailed developments of those generic models. ISD N User- Net work In terfaces The concept of reference configurations was first used in the ISDN work to describe the topological association of functional groupings at the user to network interface points. In fact Recommendation T/GSI 04-01 is the c
13、omplete description of these particular reference configurations. The key factors in the definition of reference configurations in Recommendation T/GSI 04-01 are the concepts of functional groupings and reference points. CCITT Recommendations X.30 and X.31 (1.461 and 1.462) Recommendations X.30 and
14、X.31 on the adaption of X.21 and X.25 based DTEs to the ISDN also use the concept of reference configurations to explain the topological configuration of functional groupings in- volved in these kinds of terminals accessing the ISDN. DETAILED PROPOSALS FOR REFERENCE CONFIGURATIONS FOR ISDN CONNECTIO
15、N TYPES Definition As can be inferred from Recommendation T/GSI 04-01, a reference configuration is defined to be ?a conceptual configuration based on association rules of functional groupings and reference points.? Principles for developing reference configurations In Recommendation T/GSI 03-03 the
16、 concept of connection elements is introduced. These are portions of the connection type which are identifiable as having a nature and characteristics which are sufficiently different from each other as to enable partitioning of the reference configuration of the overall connection type. Because of
17、the complicated nature and evolutionary potential of the ISDN, it is not possible to internatio- nally specify a detailed end-to-end reference connection (like CCITT Recommendation X.92 for data networks). Consequently a functional approach is adopted to specifying the structure of the ISDN connecti
18、on types, at least in the national portions. In the international portion a more detailed approach needs to be used, and in this case the structure of CCITT Recommendation G.801 is used. Overall the concept of the ISDN connection elements can be usefully used to demarcate the different sections of t
19、he reference configuration. Edition of October 31, 1987 CEPT T/GSI*03-05 E M 2326414 0005583 4 M TIGSI 03-05 E Page 3 2.3. Connection elements Recommendation T/GSI 03-03 describes three kinds of connection elements, viz: - Access; - National transit; - International transit. These are used below as
20、the basic building blocks for the connection type reference configurations. Figure 1 (T/GSI 03-05) summarises these concepts, and shows their relative disposition. 2.4. Specific Reference Configurations The general reference model given in Recommendation T/GSI 03-03 needs now to be associated with s
21、pecific connection types in order to develop specific reference configurations. However, Recommendation T/GSI 03-04 allows for so many variations in its different attributes, leading to a very large number of potential connection types, that is necessary to consider only certain dominant attributes
22、in order to produce a simpler list of reference configurations. It is suggested that for an initial analysis, only the first two of the four dominant attributes listed in Recommendation T/GSI 03-04 need to be considered. Therefore the “information transfer mode” and “information transfer rate” will
23、lead to three general classes of ISDN connection types, viz: - circuit - 64 kbit/s - (broadband) 64 kbit/s - packet The other two dominant attributes (“information transfer capability” and “establishment of connection”) do not seem to require separate reference configurations but will manifest thems
24、elves by different perfor- mance values. 2.4.1. The 64 kbt/s Class This class includes connection types 1-9 of Table 2 of Recommendation T/GSI 03-04, that is unrestricted digital, speech and voiceband information transfer capabilities; and switched, semi-permanent and perma- nent establishments. The
25、 variation of the information transfer capability is determined by the network performance parameter values allocated to each portion of the connection. For example, use of digital speech interpolation in the international connection element would restrict the connection type to speech. Likewise the
26、 differences between permanent connection types and demand connection types would manifest themselves in differen- ces in the values of parameters such as connection establishment time, etc. This approach means that there is a simple number of reference configurations but that all of the different c
27、onnection types listed in Recommendation T/GSI 03-04 would need to be tabulated for the allocation of performance values. Figures 2 (T/GSI 03-05) and 3 (T/GSI 03-05) show the reference configurations that are proposed for this class of ISDN connection types. Recommendation X.3 1 illustrates the scen
28、arios involved in providing packet switched capability in the ISDN. These are in fact reference configurations for the access connection element. Possible reference configurations for this class are shown in Figures 4 (T/GSI 03-05) and 5 (T/GSI 03-05). It should be noted that the Recommendations in
29、the X.130 series also use the concepts of national and international portions of the connection for the purposes of the allocation of the division of network performance parameter values. In those cases the boundary between the national and international portions is in the middle of the Internationa
30、l Data Switching Exchange (IDSE) (or International Switching Centre ISC). Further study is required to see if this approach should be taken in the ISDN. Further study is required to determine what the salient features of this class of ISDN connection types are. According to Recommendation T/GSI 03-0
31、4 it would include permanent and semi-permanent connections at 384, 1,536 (*) or 1,920 kbit/s. (*) Note. This information transfer rate will not be used to support calls between customers belonging to different European ISDNs as well as between customers belonging to one European ISDN. 2.4.2. The Pa
32、cket Class 2.4.3. The Broadband Class Edition of October 31, 1987 3 CEPT T/GSI*03-05 E D 2326414 0005582 b I I - - T/GSI 03-05 E Page 4 - - . I Locai National National Local CRF CRF CRF CRF CRF CRF SIT Sir I k IRP IRP IRP IRP I w I I I I I I I Access I National i International I National I Access I
33、I CE I CE I CE I CE 1 CE t l IRP: Internal Reference Point. I Figure 1 (T/GSI 03-05). Reference Configuration of Public ISDN Connection Type. Local I/ I ; II I i I i , See Figure 1/Q.512. l I i.-. I rn S = 64 kbit/s Circuit Switch. C = Signalling Handling + Exchange Control Functions. Figure 2 (T/GS
34、I 03-05). Reference Configuration (Moderate Length) 64 kbit/s Circuit Group (Overall Length 11,000 km). Edition of October 31. 1987 CEPT T/GSI*03-05 E 232b414 0005583 8 National - Access CE Transit CE - b - 1 2 .s oc O cl S I- 1 n“t= Edition of October 31, I987 I ,I 1 k l TIGSI 03-05 E CEPT T/GSI*03-05 E 232b414 0005584 T T/GSI 03-05 E Page 6 I- - -1 Edition of October 31, 1987 a a CEPT T/GSI*03-05 E 2326434 0005585 II m T/GSI 03-05 E Page 7 r- -1 Access rA Transit Link I +I I Il I I I d O Il i ri vi z O
