Corporate Telecommunication Networks
- Signalling Interworking between QSIG and H.323 - Call Completion
This Standard specifies signalling interworking between "QSIG"
and "H.323" in support of call completion supplementary services
within a Corporate telecommunication Network (CN).
"QSIG" is a signalling protocol that operates at the Q reference
point between Private Integrated services Network eXchanges (PINX)
within a Private Integrated Services Network (PISN). The Q reference
point is defined in ECMA-133
. A PISN
provides circuit-switched basic services and supplementary services
to its users. QSIG is specified in other Ecma Standards, in particular
(call control in support of
basic services), ECMA-165
protocol for the support of supplementary services) and a number
of standards specifying individual supplementary services. ECMA-186
specifies the QSIG protocol in support of call completion 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.450.9 specifies the H.323 protocol
in support of call completion services.
H.450.9 applies only to the 1998 version of H.323 (also known
as H.323 version 2) and to later versions.
In both ECMA-186
(QSIG) and ITU-Recommendation
H.450.9 (H.323), the call completion supplementary services are
Completion of Calls to Busy Subscribers (SS-CCBS) and Completion
of Calls on No Reply (SS-CCNR). These supplementary services apply
after a call establishment attempt has failed because the called
user was busy or not available, and provide means to re-establish
the call when the called user becomes available. Interworking
between QSIG and H.323 permits a call originating at a user of a
PISN to terminate at a user of a private IP network, or a call originating
at a user of a private IP network to terminate at a user of a PISN.
In such a scenario, this Standard allows the completion of calls
when the called user becomes available after having been busy (SS-CCBS),
or having not answered the original call (SS-CCNR).
Interworking between a PISN employing QSIG and a public IP network
employing H.323 is outside the scope of this Standard. However,
the functionality specified in this Standard is in principle applicable
to such a scenario when deployed in conjunction with other relevant
functionality (e.g., number translation, security functions, etc.).
This Standard is applicable to any interworking unit that can
act as a gateway between a PISN employing QSIG and a private IP
network employing H.323.
The following file can be freely downloaded:
||Acrobat (r) PDF file
This Ecma publication is also approved as ISO/IEC 21991.