Scope
In this standard, the minimal set of bearer services for the primary rate interface for the integrated serv¬ices digital network (ISDN) that conforms closely to the architectural concepts described by CCIIT are defined. The telecommunications environment in the United States for the ISDN primary rate interface is explicitly considered. The bearer services defined in this standard are the minimal set of services defined in Bearer Services Supponed by an ISDN, CCIIT
Recommendation 1.211,1 which are to be supported by public networks for the primary rate interface. The description method used by the CCIIT. which is called the method for the characterization of tele¬communication services supponed by an ISDN and network capabilities of an ISDN, is summarized in Section 4, and the description of the essential bearer services that should be supported by a public ISDN in the United States follows in Section 5. The signal¬ing procedures for these bearer services are defined in American National Standard for Telecommunica¬tions - Integrated Services Digital Network (ISDN) ¬Data-Link Layer Signalling Specification for Appli¬cation at the User-Network Interface, ANSI Tl.602¬ 1989, and American National Standard for Telecom¬munications - Integrated Services Digital Network (ISDN) - Layer-3 Signalling Specification for Cir¬cuit-Switched Bearer Service for Digital Subscriber Signalling System Number 1 (DSSSI), ANSI Tl.607.2 A standard for digital communications be¬tween the user and network equipments is currently under development. 1 The designation nwnbers for the CCITT Recommendations that appear in this standard refer to the 1984 CCITT Red Book. Contact the secretariat for more recent information. 2This standard is currently under development. Contact the secretariat for more recent information.
1.1
The Minimal Set of Bearer Services.
The intent of this standard and its relationship to ANSI T1.602-1989 and Tl.6072 are:
(1) The services defined in this standard are con¬sidered to be essential for provision by public net¬works. The availability of these services may depend on the subscription profile of the user. This core set of services is required as a solid foundation on which subsequent ISDN standards may be built. Subse¬quent standards can include nonessential bearer serv¬ices and supplementary services.
(2) ANSI T1.602-1989 and T1.6072 include sig¬naling procedures for those bearer services described in this standard.
(3) Customer premises equipment implementa¬tions, when viewed from the user-public-network interface, need only implement the procedures de¬ scribed in ANSI T1.602-1989 and Tl.60?2 that are associated with the minimal set of bearer service(s) supported by that equipment; for example, a voice¬only terminal equipment (TE) could implement only the procedures for circuit-mode speech (bearer capa¬bility information element, and the like) and not implement those for circuit-mode digital.
(4) Devices that suppon the bearer services de¬fined in this standard by implementing associated procedures described in other American National Standards and using the default parameters and other specified mandatory parameters are expected to inter¬operate successfully. (Successfully means that they work together to obtain/provide the appropriate bearer service.)
1.2
Relationsbip to Capabilities beyond the Mini. mal Set of Bearer Services. It is likely that ISDN implementations will provide capabilities beyond those dermed in this standard. Some of these capa¬bilities will eventually be standardized while others will be specific to an implementation. The following 9
AMERICAN NATIONAL STANDARD T1.603-1990 guidelines derme the relationship of these additional capabilities to this standard.
(I) The network, when viewed from the user-net¬work interface, may also provide other additional ser¬vices, capabilities, protocols, functions, and proce¬dures not described in this standard or any American National Standard. These mayor may not be evoked by a particular user at a particular user-public-net¬work interface.
(2) Customer premises equipment may implement additional services, capabilities, protocols, functions, and procedures not described in this standard or the American National StandArd on signaling (ANSI TI.6071). These mayor may not be supported by a particular network at a particular user-network inter¬face.
(3) The implementation of the additional aspects mentioned in the previous two points does not., there¬fore, make the user or network noncompliant with this standard or with ANSI T1.602-1989 and T1.60'P.
(4) Some or all of the additional aspects men¬tioned in 1.2(1) and 1.2 (2) may be described in other standards; for example, standard signaling for a stan¬dard supplementary service.
