ISO/IEC 21411:2001

Information technology — Telecommunications and information exchange between systems — Corporate telecommunication networks — Signalling interworking between QSIG and H.323 — Call diversion supplementary services

Scope

This International Standard specifies signalling interworking between "QSIG" and "H.323" in support of call diversion
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. ISO/IEC 13873 specifies the
QSIG protocol in support of call diversion 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). Recommendation H.450.3
specifies the H.323 protocol in support of call diversion services.
NOTE - H.450.3 applies only to the 1998 version of H.323 (also known as H.323 version 2) and to later versions.
In both ISO/IEC 13873 (QSIG) and ITU-Recommendation H.450.3 (H.323), the call diversion supplementary services are Call
Forwarding Unconditional (SS-CFU), Call Forwarding Busy (SS-CFB), Call Forwarding No Reply (SS-CFNR) and Call
Deflection (SS-CD). These supplementary services apply during call establishment and provide diversion of an incoming call to
another destination.
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. This International Standard provides the following
additional capabilities:
_ a call originating from a PISN and destined for a user of an H.323 network to be diverted by the H.323 network to an
alternative destination;
_ a call originating from an H.323 network and destined for a user of a PISN to be diverted by the PISN to an alternative
destination;
_ a call destined for a user of a PISN to be diverted to an alternative destination where that alternative destination is in an
H.323 network;
_ a call destined for a user of an H.323 network to be diverted to an alternative destination where that alternative destination
is in a PISN.
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.