scope:

The present document specifies the stage three of on-demand connection-oriented release 1 basic telecommunication services for the pan-European Broadband Integrated Services Digital Network (B-ISDN) as provided at the T_B reference point or coincident SB and T_B reference point (as defined in lTU-T Recommendation 1.413 [19]) by means of the Digital Subscriber Signalling System No. two (DSS2) protocol. Stage three identifies the protocol procedures and switching functions needed to support a telecommunications service (see CCITT Recommendation 1.130 [59]).

In addition, the present document specifies the protocol requirements at the T_B reference point where the service is provided to the user via a private B-ISDN.

NOTE 1: Procedures at the T_B reference point, to support the access of a private B-ISDN to the public B-ISDN, are not explicitly identified in the present document, however, some procedures are applicable only at the T_B reference point.

The present document also specifies the particular features required to provide 64 kbit/s based circuit-mode ISDN services in B-ISDN and to support access interworking between B-ISDN and N-ISDN.

A basic telecommunications service is a fundamental type of service. It forms the basis on which supplementary services may be added.

NOTE 2: Specific requirements of individual B-ISDN connection-oriented basic telecommunication services are not covered by the present document.

Further parts of the present document provide the method of testing and detailed application specific requirements to determine conformance to the present document.

The present document is applicable to equipment supporting connection-oriented basic B-ISDN telecommunication services, to be attached at either side of a T_B reference point or coincident S_B and T_B reference points when used as an access to the public B-ISDN.