1、 TGS Page 1 E Recommendation T/GSI 01-06 (by correspondence, June 1987) EVOLUTION TOWARDS ISDN Recommendation proposed by the Special Group Integration (GSI) Text of the Recornmendation adopted by the “Telecommimicatioiis” Commission: “The European Conference of Posts and Telecommunications Administ
2、rations, considerittg - 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 Administrations to have more precise answe
3、rs 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 define material from CCITT Recommendations, promote and strengthe
4、n European harmonisation, O recommends to the members of the CEPT, that they evolve their telecommunication networks towards ISDN according to the specifications given in the attached text”. Edition of October 31, 1987 CEPT T/GSI*OL-Ob E 7 232b414 0005323 4 T/GSI 01-06 E Page 2 1. 2. 2.1. 2.2. 2.3.
5、2.4. GENERAL Considering that ISDN is defined in Recommendation T/GSI 01-02 i, CEPT Administrations Recom- mend that the evolution towards ISDN in the European networks be in accordance with the guidelines given in this Recommendation. The ISDN is considered to be a natural evolution of the existing
6、 telephone networks, and specially from the Integrated Digital Network (IDN). It is Recommended that in a number of domains strict compatibility must be ensured: - interfaces must comply with the relevant CEPT Recommendations and specially interfaces for the - in the case of basic access, the physic
7、al interfaces at the S and T reference points must be identical; - this terminal interface should also be offered by PABX manufacturers so that common design of The above mentioned points are part of the necessary means for providing terminal portability in the European countries. The evolution towa
8、rds ISDN may be divided into a number of steps: - Step 1 : Digital connectivity between exchanges. - Step 2: Common channel signalling CCITT No. 7 (see bellow). - Step 3: Introduction of digital subscriber unit having the capability of connecting both analog or digital lines, the latter using the D-
9、channel protocol as signalling. - Step 4: Introduction of additional functions for accessing the dedicated networks. - Step 5: Addition to the access functions to provide supplementary services. - Step 6: Addition of ISDN broadband capabilities. Some of these steps may be combined, resequenced or ma
10、y not exist according to the different national situations. terminals ; terminals can be achieved. NETWORK ASPECTS A number of areas must be considered for the evolution of the European networks towards ISDN: Interconnection of the different national networks It is understood that in the future this
11、 interworking will be realized by means of CCITT No. 7, ISUP, however as an interim solution it is recommended to implement an enhanced version of the TUP as defined in the CCITT red book. This revised version is described in Recommendation T/GSI 04-03 121 and is limited to cover the requirements fo
12、r the first introduction of ISDN in Europe. Switching The basis for switching is the 64 kbit/s circuit switched connection. The Recommendations are in accordance with the Q.5xx series with some modifications specific to Europe, these modifications are indicated in Recommendations T/GSI 03-09 3. Inte
13、rworking between ISDN and dedicated networks - Telephone networks: Different national versions of signalling system CCITT No. 7 have already been implemented in a number of countries, it is however recommended that as soon as a stable version of ISUP is available, actions be taken to align the diffe
14、rent national versions where possible. The rules to be applied for interworking are indicated in the T/GSI 05 series. Further study required. - Packet networks: Interworking between services This interworking situation may accur not only between different services but also between variants of the sa
15、me service. Edition of October 31, 1987 CEPT T/GSI*OL-Ob E 7 232b414 0005324 - b _ - T/GSI O1 -06 E Page 3 Compatibility between terminals can only be achieved, if all the layers for the basic service are the same. For the time being different options of a same service have been implemented in diffe
16、rent countries. Studies are still proceeding on this future compatibility. As soon as stabilized results are agreed it will be of the utmost importance that action is taken to apply these new recommendations. During the introduction phases of ISDN (commercial phases) the backward compatibility betwe
17、en the protocols must be ensured. 3. SERVICES One of the most important interest of ISDN is the capability of providing a large amount of services and supplementary services to subscribers. For rapidly developing ISDN in Europe in an harmonized way it is important to open the services in a coordinat
18、ed way on an international basis. Starting from 1988, which is considered as a realistic date for the introduction of ISDN, the following services are Recommended: - Bearer services: - Teleservices : - Circuit switched 64 kbit/s unrestricted - Telephony 3.1 kHz at 64 kbit/s - Facsimile at 64 kbit/s
19、(groupe IV) - Teletex at 64 kbit/s - Mixed mode Teletex/facsimile at 64 kbit/s - Supplementary services: - Call waiting - Calling line identification - Closed user group - Direct dialling in - Terminal portability (on the same interface) At a later stage other services and supplementary services cou
20、ld also be considered: - Bearer services: - Teleservices in the B channel - Packet bearer service in the D channel - Telephony 7 kHz at 64 kbit/s - Videotex alphageometric at 64 kbit/s - Transmission of images - Intercommunication between computers at 64 kbit/s - Charging informations - Call complet
21、ion to busy subscriber - Conference call - Diversion - Freephone - Malicious call identification - Three party call - Called line identification - Other supplementary services could be introduced earlier or later: Sub-addressing and user to user signalling in call control messages, even if specified
22、, may be introduced only in the second phase. Other services are foreseen but have not yet been really considered and will be introduced later in the Recommendations. 4. TERMINALS, TERMINAL ADAPTORS In order to provide ISDN services to users, it is highly recommended to specify the relevant ISDN-ter
23、minals in accordance with the ISDN-User-Network interface Recommendation (set T/GSI 04-02) 4. Nevertheless existing terminals will still be used in ISDN, they will be connected to the S interface by means of terminal adaptors, the following are internationally specified : - X.25 6 on the B channel A
24、t a later stage the following will be defined: - Adaptor for asynchronous terminals (V.24) 8. -X.21 5 - X.2lbi. 7 Edition of October 31, 1987 CEPT T/GSI*OL-Ob E 7 2326434 0005325 B - - T/GSI Page 4 REFERENCES CEPT Recommendation T/GSI 01-02. ISDN dejnition. CEPT Recommendation T/GSI 04-03. Interchan
25、ge signalling. CEPT Recommendation T/GSI 03-09. Switching. CEPT Recommendation T/GSI 04-02. User to Network interfaces and protocols (set of thee Recommenda- tons) * CCITT Recommendation X.2 1. Intelface between data terminal equipment (DTE) and data circuit-teriiiatiig equipment (DCE) for synchrono
26、lts operation on public data networks. CCITT Recommendation X.25. Interface betweea data terininal equipment (DTE) and data circiiit-tertittatiig equipment (DCE) for terminals operating in the packet mode and connected to public data networks by dedicated circtiit. CCITT Recommendation X.2lbis. Use
27、on public data networks of data terminal equipment (DTE) which is designed for inteifacing to synchronous V-series modems. CCITT Recommendation V.24. List of dejnitions for interchtige circuits between data terminal equipment and data circuit-terminating equipment. I-“r O Edition of &tober 31, 1987
