ISO/IEC 21991:2002
(Main)Information technology — Telecommunications and information exchange between systems — Corporate Telecommunication Networks — Signalling interworking between QSIG and H.323 — Call completion supplementary services
Information technology — Telecommunications and information exchange between systems — Corporate Telecommunication Networks — Signalling interworking between QSIG and H.323 — Call completion supplementary services
ISO/IEC 21991:2002 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 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 13870 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. NOTE 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 ISO/IEC 13870 (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, ISO/IEC 21991:2002 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 ISO/IEC 21991:2002. However, the functionality specified in ISO/IEC 21991:2002 is in principle applicable to such a scenario when deployed in conjunction with other relevant functionality (e.g., number translation, security functions, etc.). ISO/IEC 21991:2002 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.
Technologies de l'information — Télécommunications et échange d'information entre systèmes — Réseaux de télécommunications de corps — Travail de signalisation entre QSIG et H.323 — Compléments de service d'achèvement d'appel
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INTERNATIONAL ISO/IEC
STANDARD 21991
First edition
2002-06-15
Information technology —
Telecommunications and information
exchange between systems — Corporate
Telecommunication Networks — Signalling
interworking between QSIG and H.323 —
Call completion supplementary services
Technologies de l'information — Télécommunications et échange
d'information entre systèmes — Réseaux de télécommunications de
corps — Travail de signalisation entre QSIG et H.323 — Compléments de
service d'achèvement d'appel
Reference number
©
ISO/IEC 2002
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ii © ISO/IEC 2002 – All rights reserved
Contents Page
Foreword v
Introduction vi
1 Scope 1
2 Conformance 1
3 Normative references 1
4 Definitions 2
4.1 External definitions 2
4.2 Other definitions 2
4.2.1 Entity A 2
4.2.2 Entity B 2
4.2.3 Gateway 2
4.2.4 IP network 2
4.2.5 Leg A 2
4.2.6 Scenario A1 2
4.2.7 Scenario A2 2
5 Acronyms 3
6 Service architecture 3
6.1 Service architecture for invocation and operation 3
6.1.1 ISO/IEC 13870 service architecture 3
6.1.2 H.450.9 service architecture 4
6.1.3 Scenarios for interworking 4
6.1.4 Selection of the same gateway for all phases 4
6.2 Options 4
7 Protocol interworking – General requirements 5
8 Protocol interworking – Messages and APDUs 5
8.1 Signalling phase 1 - invocation of call completion 5
8.1.1 Scenario A1 5
8.1.2 Scenario A2 6
8.2 Signalling phase 2 – user B available notification 6
8.2.1 Scenario A1 7
8.2.2 Scenario A2 8
8.3 Signalling phase 3 – CC call establishment 9
8.3.1 Scenario A1 9
8.3.2 Scenario A2 9
8.4 Signalling phase 4 – cancellation of SS-CC 9
8.4.1 Scenario A1 10
8.4.2 Scenario A2 10
9 Protocol interworking – content of APDUs 10
9.1 APDU content mapping from QSIG to H.323 11
© ISO/IEC 2002 – All rights reserved iii
9.1.1 ccbsRequest/ccnrRequest invoke APDU mapping 11
9.1.2 ccbsRequest/ccnrRequest return result APDU mapping 11
9.1.3 ccCancel/ccExecPossible invoke APDU mapping 11
9.2 APDU content mapping from H.323 to QSIG 12
9.2.1 ccbsRequest/ccnrRequest invoke APDU mapping 12
9.2.2 ccbsRequest/ccnrRequest return result APDU mapping 12
9.2.3 ccCancel/ccExecPossible invoke APDU mapping 12
Annexes
A - Implementation Conformance Statement (ICS) proforma 13
B - Message flow examples 20
iv © ISO/IEC 2002 – All rights reserved
Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical Commission) form the
specialized system for worldwide standardization. National bodies that are members of ISO or IEC participate in the
development of International Standards through technical committees established by the respective organization to deal with
particular fields of technical activity. ISO and IEC technical committees collaborate in fields of mutual interest. Other
international organizations, governmental and non-governmental, in liaison with ISO and IEC, also take part in the work. In the
field of information technology, ISO and IEC have established a joint technical committee, ISO/IEC JTC 1.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3.
The main task of the joint technical committee is to prepare International Standards. Draft International Standards adopted by
the joint technical committee are circulated to national bodies for voting. Publication as an International Standard requires
approval by at least 75 % of the national bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this International Standard may be the subject of patent rights.
ISO and IEC shall not be held responsible for identifying any or all such patent rights.
ISO/IEC 21991 was prepared by ECMA (as ECMA-326) and was adopted, under a special “fast-track procedure”, by Joint
Technical Committee ISO/IEC JTC 1, Information technology, in parallel with its approval by national bodies of ISO and IEC.
Annex A forms a normative part of this International Standard. Annex B is for information only.
© ISO/IEC 2002 – All rights reserved v
Introduction
This International Standard is one of a series of Standards defining the interworking of services and signalling protocols
deployed in Corporate telecommunication Networks (CNs). The series uses telecommunication concepts as developed by
ITU-T and conforms to the framework of International Standards on Open Systems Interconnection as defined by ISO/IEC.
This International Standard defines the signalling protocol interworking for call completion supplementary services between a
Private Integrated Services Network (PISN) and a packet-based private telecommunication network based on the Internet
Protocol (IP). It is further assumed that the protocol for the PISN part is that defined for the Q reference point (QSIG) and that
the protocols for the IP-based network are based on ITU-T Recommendation H.323.
This International Standard is based upon the practical experience of ECMA member companies and the results of their active
and continuous participation in the work of ISO/IEC JTC 1, ITU-T, ETSI and other international and national standardization
bodies. It represents a pragmatic and widely based consensus.
vi © ISO/IEC 2002 – All rights reserved
INTERNATIONAL STANDARD ISO/IEC 21991:2002(E)
Information technology — Telecommunications and information exchange between
systems — Corporate Telecommunication Networks — Signalling interworking
between QSIG and H.323 — Call completion supplementary services
1 Scope
This International 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 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 13870
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.
NOTE - 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 ISO/IEC 13870 (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
International 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
International Standard. However, the functionality specified in this International 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 International 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.
2 Conformance
In order to conform to this International Standard, a gateway shall satisfy the requirements identified in the Implementation
Conformance Statement (ICS) proforma in annex A.
3 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of this
International Standard. For dated references, subsequent amendments to, or revisions of, any of these publications do not
apply. However, parties to agreements based on this International Standard are encouraged to investigate the possibility of
applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the
normative document referred to applies. Members of ISO and IEC maintain registers of currently valid International Standards.
ISO/IEC 11572:2000, Information technology — Telecommunications and information exchange between systems — Private
Integrated Services Network — Circuit mode bearer services — Inter-exchange signalling procedures and protocol
ISO/IEC 11579-1:1994, Information technology — Telecommunications and information exchange between systems — Private
integrated services network — Part 1: Reference configuration for PISN Exchanges (PINX)
© ISO/IEC 2002 – All rights reserved 1
ISO/IEC 11582:1995, Information technology — Telecommunications and information exchange between systems — Private
Integrated Services Network — Generic functional protocol for the support of supplementary services — Inter-exchange
signalling procedures and protocol
ISO/IEC 13870:2001, Information technology — Telecommunications and information exchange between systems — Private
Integrated Services Network — Inter-exchange signalling protocol — Call completion supplementary services
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
ITU-T Rec. H.225.0, Call signalling protocols and media stream packetization for packet-based multimedia communication
systems
ITU-T Rec. H.245, Control protocol for multimedia communication
ITU-T Rec. H.323, Packet-based multimedia communications systems
ITU-T Rec. H.450.1:1998, Generic functional protocol for the support of supplementary services in H.323
ITU-T Rec. H.450.9:2000, Call Completion Supplementary Services for H.323
4 Definitions
For the purposes of this International Standard, the following definitions apply.
4.1 External definitions
This International Standard uses the following terms defined in other documents:
– Call (ISO/IEC 21409)
– Corporate telecommunication Network (CN) (ISO/IEC 21409)
– Endpoint (ITU-T Rec. H.323)
– Gatekeeper (ITU-T Rec. H.323)
– Private Integrated Services Network (PISN) (ISO/IEC 21409)
– Private Integrated services Network eXchange (PINX) (ISO/IEC 11579-1)
Additionally the definitions in ISO/IEC 13870 and ITU-T Recommendation H.450.9 apply as appropriate.
4.2 Other definitions
4.2.1 Entity A
Signalling entity at the PINX or H.323 endpoint serving the calling user (user A).
4.2.2 Entity B
Signalling entity at the PINX or H.323 endpoint serving the called user (user B).
4.2.3 Gateway
A gateway as defined in H.323 specifically for the purpose of interworking with a network employing QSIG.
4.2.4 IP network
A network, unless otherwise stated a CN, offering connectionless packet-mode services based on the Internet Protocol (IP) as
the network layer protocol.
4.2.5 Leg A
Call segment that lies between entity A and entity B.
4.2.6 Scenario A1
Interworking arrangement in which entity A (PINX A) is in the PISN and entity B is in the IP network.
4.2.7 Scenario A2
Interworking arrangement in which entity A (endpoint A) is in the IP network and entity B is in the PISN.
2 © ISO/IEC 2002 – All rights reserved
5 Acronyms
APDU Application Protocol Data Unit
CN Corporate telecommunication Network
ICS Implementation Conformance Statement
IP Internet Protocol
PINX Private Integrated services Net
...
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