scope:

General

The Integrated Services Digital Network (ISDN) User Part (UP) defines the protocol which supports the signaling functions required to provide voice and non-voice services in an Integrated Services Digital Network.

The ISDN User Part (ISUP) is also suited for application in dedicated telephone and circuit switched data networks and in analogue and mixed analogue/ digital networks. The ISDN User Part is based on, and uses wherever applicable the same signaling procedures, information elements and message types as the internationally specified ISDN User Part of ITU-T Signaling System No.7 (SS7), as described in:

Q.730 (2000), ISDN supplementary services.²

Q.761 (2000), Functional description of the ISDN user part.²

Q.762 (2000), General function of messages.²

Q.763 (2000), Formats and codes.²

Q.764 (2000), Signaling procedures.²

Q.766 (1992), Performance objectives in the ISDN applications.²

The ISDN User Part is also based on and aligned with:

Q.850 (1996), Usage of Cause and Location in the Digital Subscriber Signaling System No. 1 and the Signaling System No. 7 ISDN User Part.²

T1.607-2000 (R2004) American National Standard for Telecommunications - Digital Subscriber Signaling System No. 1 (DSS1) - Layer 3 Signaling Specification for Circuit Switched Bearer Service.³

In addition, the ISDN User Part is aligned with:

Q.724 (1988), Telephone user part signaling procedures.²

In addition the ISDN User Part protocol is flexible enough and has sufficient spare capacity to accommodate any foreseeable requirements that may be imposed by the introduction of new supplementary services and network capabilities.

The services of the Signaling System No.7 Message Transfer Part (MTP) and, in some cases, of the Signaling System No.7 Signaling Connection Control Part (SCCP) are used to effect the transfer of signaling information between communicating ISDN User Parts. The MTP is described in:

ATIS-1000111.2005, American National Standard for Telecommunications - Signaling System Number 7 (SS7) - Message Transfer Part (MTP).³

and the SCCP is described in:

ATIS-1000112.2005, American National Standard for Telecommunications - Signaling System Number 7 (SS7) - Signaling Connection Control Part (SCCP).³

The ISDN User Part is specified in Chapters ATIS-1000113.1 to ATIS-1000113.7 of the American National Standards Specification of Signaling System No.7. A general description of ISDN User Part signals and messages is provided in Chapter ATIS-1000113.2. Message formats and message field codings are specified in Chapter ATIS-1000113.3, while signaling procedures are described in Chapter ATIS-1000113.4 and performance objectives in Chapter ATIS-1000113.5. Chapter ATIS-1000113.6 contains the state transition diagrams for the ISDN User Part. Chapter ATIS-1000113.7 specifies the Application Transport Mechanism (APM).

This chapter may contain requirements that reference other American National Standards. If so, when American National Standards referenced in the requirements are superseded by revisions approved by the American National Standards Institute, Inc, the revisions shall apply.

Applicability to Other Standards.

A number of messages and parameters are described which are part of the ITU-T ISDN User Part Recommendations but for which there are currently no procedures specified in American National Standards. The signaling messages and parameters that fall into this category are marked with the note "no procedure specified for U.S. networks".

² This document is available from the International Telecommunications Union. < http://www.itu.int/ITU-T/ >

³ This document is available from the Alliance for Telecommunications Industry Solutions, 1200 G Street N.W., Suite 500, Washington, DC 20005.