Scope
In this standard, the minimal set of bearer services for the basic rate interface for the integrated services digital network (ISDN) that conforms closely to the architectural conceptS described by CCIIT are de¬fined. The telecommunications environment in the United States for the ISDN basic rate interface is explicitly considered. The bearer services defmed in this standard are the minimal set of services defined in Bearer Services Supported by and ISDN, CCIIT Recommendation 1.211,1 which are to be supported by public networks for the ISDN basic rate interface. The description method used by ccm, which is called the method for the characterization of tele¬commURication services supported 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¬mg procedures for these bearer services are defmed in American National Standard for Telecommunica¬tions - Integrated Services Digital Network (ISDN) ¬Data-Link Layer Signalling Specification for Appli¬cation at the User-Network InteIface, ANSI Tl.602¬1989. American National Standard for Telecommuni¬cations - Integrated Services Digital Network (ISDN) - Layer-3 Signaling SpecIfication for Circuit¬Switched Bearer Service for Digital Subscriber Sig¬naling System Number 1 (DSSS1), ANSI Tl.607,2 and American National Standard for Telecommunica¬ 1 The designation nmnbeIS for the ccrrr Recommendations lhat appear in this standard refer to the 1984 ccrrr Red Book. Contact the secretariat for more recent infomta1ion. 2This standard is cmrently weier devclopmenL Conract the secretariat for more recent information.
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tions - Integrated Services Digital Network (ISDN) ¬Layer-3 Signaling Specification for X.25 Packet¬Switched Bearer Service for Digital Subscriber Sig¬naling System Number 1 (DSSSI). ANSI Tl.608.2 Digital communication between the user and the network equipments is defined in American National Standard for Telecommunications - Integrated Serv¬ices Digital Network (ISDN) - Basic Access Inter¬face for Use on Metallic Loops for Application on the Network Side of the NT (Layer I Specification), ANSI Tl.601-1988, and American National Standard for Telecommunications - Integrated Services Digital Network (ISDN) - Basic Access Interface for S and T Reference Points (Layer 1 Specification), ANSI TI.605-1989.
1.1
The Minimal Set of Bearer Services. The intent of this standard and itS relationship to ANSI TI.601-1988, Tl.602-1989, Tl.605-1989, Tl.607,2
and Tl.6082 are:
(I) 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. Subsequent standards can include nonessential bearer services and supplementary services.
(2) ANSI Tl.601-1988. Tl.602-1989. Tl.60S¬1989, Tl.607,2 and T1.6082 include signaling proce¬dures for those bearer services described in
this stan¬dard.
(3) Customer premises equipment implementa¬tions, when viewed from the user-public-network interface. need only implement the procedures de¬scribed in ANSI Tl.601-1988. Tl.602-1989, T1.605¬1989. Tl.607.2 and Tl.6082 that are associated with the minimal set of bearer service(s) supported by that equipment; for example, a voice-only terminal.equip¬ment (TE) could implement only the procedures for circuit-mode speech (bearer capability
information element, and the like) and not implement those for circuit- mode digital.
(4) DeviceS that suppon the bearer services de¬tined 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.)
L2 Relationship to Capabilities beyond the Mini¬mal Set of Bearer Senices. 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 guidelines define the relationship of these additional capabilities to this standard.
(1) The network, when viewed from the user-network interface, may also provide other addi¬tional services, capabilities, protocols, functions. and procedures not described in this standard or any American Nation8I Standard. These mayor may not be invoked by a particular user at a particular user-public-network interface.
(2) Customers premises equipment may imple¬ment additional services. capabilities. protocols, functions, and procedures not described in this stan¬dard or the American National Standards on signal¬ing (Tl.60P and Tl.6082). These may or may not be supported by a particulaf network at a particular user-network interface.
(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 Tl.601-1988, Tl.602¬1989. Tl.60S-1989. T1.607,z and T1.608.z
(4) Some or all of the additional aspects men¬tioned in 1.2(1) and 1.2 (2) may be described in other standards; e.g., standard signaling for a
standard supplementary service.
