ISO/IEC 21409:2001

Information technology — Telecommunications and information exchange between systems — Corporate telecommunication networks — Signalling interworking between QSIG and H.323 — Generic functional protocol for the support of supplementary services ISO/IEC 21409:2001

Scope

This International Standard specifies signalling interworking between "QSIG" and "H.323" in support of generic functional
procedures for supplementary services within a Corporate telecommunication Network (CN).
"QSIG" is a signalling protocol that operates at the Q reference point between Private Integrated Services eXchanges (PINX)
within a Private Integrated Services Network (PISN). The Q reference point is defined in ISO/IEC 11579-1. A PISN provides
circuit-switched basic services and supplementary services to its users. QSIG is specified in other Standards, in particular
ISO/IEC 11572 (call control in support of basic services), ISO/IEC 11582 (generic functional protocol for the support of
supplementary services) and a number of standards specifying individual supplementary services.
"H.323" is a set of signalling protocols for the support of voice or multimedia communication within a packet network, in
particular a packet network that uses the Internet Protocol (IP) as its network layer protocol (IP network). H.323 signalling
protocols operate between endpoints in an IP network, either indirectly via one or more gatekeepers, or directly. An endpoint
can be a terminal or a gateway to another network. H.323 is an "umbrella" recommendation, referring to various ITU-T
recommendations, in particular Recommendations H.225.0 and H.245 (basic communication capabilities) and
Recommendation H.450.1 (generic functional protocol for the support of supplementary services).
NOTE - H.450.1 applies to the 1998 version of H.323 (also known as H.323 version 2) and to later versions.
Interworking between QSIG and H.323 permits a call originating at a user of a PISN to terminate at a user of an IP network, or
a call originating at a user of an IP network to terminate at a user of a PISN. In addition this International Standard enables the
participants of a call to exchange supplementary service control information in a generic way. The more specific aspects of
interworking particular supplementary services are specified in other Standards.
This International Standard is applicable to any interworking unit that can act as a gateway between a PISN employing QSIG
and an IP network employing H.323.