Integrated Services Digital Network (ISDN); Digital Subscriber Signalling System No. one (DSS1) User-Network Interface Layer 3 Specification for Basic Call Control Part 1: Protocol Specification
This European Telecommunication Standard (ETS) specifies the stage three of circuit-mode on-demand basic telecommunication services for the pan-European Integrated Services Digital Network (ISDN) as provided by European telecommunications operators at the T reference point or coincident S and T reference point (as defined in ITU-T Recommendation I.411 [91] by means of the Digital Subscriber Signalling System No. one (DSS1). Stage three identifies the protocol procedures and switching functions needed to support a telecommunication service (see CCITT Recommendation I.130 [88]). In addition@ this ETS specifies the protocol requirements at the T reference point where the service is provided to the user via a private ISDN. NOTE 1: Procedures at the T reference point@ to support the access of a private ISDN to the public ISDN@ are not explicitly identified in this ETS@ however some procedures are applicable only to the T reference point. This ETS does not specify the additional protocol requirements where the service is provided to the user via a telecommunication network that is not an ISDN. A basic telecommunication service is a fundamental type of service. It forms the basis on which supplementary services may be added. NOTE 2: Specific requirements of individual circuit-mode basic telecommunication services are not covered in this ETS. However@ ETR 018 gives guidance on the use of service specific information elements to implement individual basic telecommunication services. Further parts of this ETS specify the Specification and Description Language (SDL) diagrams@ the method of testing and detailed application specific requirements to determine conformance based on this ETS. This ETS is applicable to equipment supporting circuit-mode on-demand basic telecommunication services@ to be attached at either side of a T reference point or coincident S and T reference point when used as an access to the public ISDN.