1、 Standard ECMA-326 June 2001 Standardizing Information and Communication Systems Corporate Telecommunication Networks Signalling Interworking between QSIG and H.323 Call Completion Supplementary Services Phone: +41 22 849.60.00 - Fax: +41 22 849.60.01 - URL: http:/www.ecma.ch - Internet: helpdeskecm
2、a.ch . Standard ECMA-326 June 2001 Standardizing Information and Communication Systems Corporate Telecommunication Networks Signalling Interworking between QSIG and H.323 Call Completion Supplementary Services Phone: +41 22 849.60.00 - Fax: +41 22 849.60.01 - URL: http:/www.ecma.ch - Internet: helpd
3、eskecma.ch IW ECMA-326.doc 05-03-02 16,31 . Brief History This Standard is one of a series of ECMA 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 con
4、forms to the framework of International Standards on Open Systems Interconnection as defined by ISO/IEC. It has been produced under ETSI work item DTS/ECMA-00215. This particular Standard defines the signalling protocol interworking for call completion supplementary services between a Private Integr
5、ated 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 Recomme
6、ndation H.323. This 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 JTC1, ITU-T, ETSI and other international and national standardization bodies. It represents a pragmatic and widely based c
7、onsensus. This ECMA Standard is contributed to ISO/IEC JTC1 under the terms of the fast-track procedure, for adoption as an ISO/IEC International Standard. This ECMA Standard has been adopted by the General Assembly of June 2001. . - i - Table of contents 1 Scope 1 2 Conformance 1 3 References 1 4 D
8、efinitions 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 3 5 Acronyms 3 6 Service architecture 3 6.1 Service architecture for invocation and operation 3 6.1.1 ECMA-186 serv
9、ice 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 5 7 Protocol interworking General requirements 5 8 Protocol interworking Messages and APDUs 5 8.1 Signalling phase 1 - invocation of call comple
10、tion 5 8.1.1 Scenario A1 6 8.1.2 Scenario A2 7 8.2 Signalling phase 2 user B available notification 7 8.2.1 Scenario A1 8 8.2.2 Scenario A2 9 8.3 Signalling phase 3 CC call establishment 10 8.3.1 Scenario A1 10 8.3.2 Scenario A2 10 8.4 Signalling phase 4 cancellation of SS-CC 10 8.4.1 Scenario A1 11
11、 8.4.2 Scenario A2 11 - ii - 9 Protocol interworking content of APDUs 12 9.1 APDU content mapping from QSIG to H.323 12 9.1.1 ccbsRequest/ccnrRequest invoke APDU mapping 12 9.1.2 ccbsRequest/ccnrRequest return result APDU mapping 12 9.1.3 ccCancel/ccExecPossible invoke APDU mapping 12 9.2 APDU conte
12、nt mapping from H.323 to QSIG 13 9.2.1 ccbsRequest/ccnrRequest invoke APDU mapping 13 9.2.2 ccbsRequest/ccnrRequest return result APDU mapping 13 9.2.3 ccCancel/ccExecPossible invoke APDU mapping 13 Annex A - Implementation Conformance Statement (ICS) proforma 15 Annex B - Message flow examples 23 1
13、 Scope 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
14、 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 ECMA-143 (call control in support of
15、basic services), ECMA-165 (generic functional 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 supp
16、ort 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 d
17、irectly. 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
18、 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 ECMA-186 (QSIG) and ITU-Recommendation H.450.9 (H.323
19、), 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
20、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 scenari
21、o, 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. Howev
22、er, 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
23、 PISN employing QSIG and a private IP network employing H.323. 2 Conformance In order to conform to this Standard, a gateway shall satisfy the requirements identified in the Implementation Conformance Statement (ICS) proforma in annex A. 3 References The following standards contain provisions which,
24、 through reference in this text, constitute provisions of this Standard. All standards are subject to revision, and parties to agreements based on this Standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. In the case of referen
25、ces to ECMA Standards that are aligned with ISO/IEC International Standards, the number of the appropriate ISO/IEC International Standard is given in brackets after the ECMA reference. ECMA-133 Private Integrated Services Network (PISN) - Reference Configuration for PISN Exchanges (PINX) (Internatio
26、nal Standard ISO/IEC 11579-1) - 2 - ECMA-143 Private Integrated Services Network (PISN) - Circuit Mode Bearer Services - Inter-Exchange Signalling Procedures and Protocol (International Standard ISO/IEC 11572) ECMA-165 Private Integrated Services Network (PISN) - Generic Functional Protocol for the
27、Support of Supplementary Services - Inter-Exchange Signalling Procedures and Protocol (International Standard ISO/IEC 11582) ECMA-186 Private Integrated Services Network (PISN) - Inter-Exchange Signalling Protocol - Call Completion Supplementary Services (International Standard ISO/IEC 13870) ECMA-3
28、07 Corporate Telecommunication Networks - Signalling Interworking between QSIG and H.323 - Generic Functional Protocol for the Support of Supplementary Services (International Standard ISO/IEC 21409) ITU-T Rec. H.225.0 Call signalling protocols and media stream packetization for packet-based multime
29、dia communication systems (1998 or later) ITU-T Rec. H.245 Control protocol for multimedia communication (1998 or later) ITU-T Rec. H.323 Packet-based multimedia communications systems (1998 or later) ITU-T Rec. H.450.1 Generic functional protocol for the support of supplementary services in H.323 (
30、1998) ITU-T Rec. H.450.9 Call completion supplementary services for H.323 (2000) 4 Definitions For the purposes of this Standard, the following definitions apply. 4.1 External definitions This Standard uses the following terms defined in other documents: Call (ECMA-307) Corporate telecommunication N
31、etwork (CN) (ECMA-307) Endpoint (ITU-T Rec. H.323) Gatekeeper (ITU-T Rec. H.323) Private Integrated Services Network (PISN) (ECMA-307) Private Integrated services Network eXchange (PINX) (ECMA-133) Additionally the definitions in ECMA-186 and ITU-T Recommendation H.450.9 apply as appropriate. 4.2 Ot
32、her 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
33、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 ar
34、rangement in which entity A (PINX A) is in the PISN and entity B is in the IP network. - 3 - 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. 5 Acronyms APDU Application Protocol Data Unit CN Corporate telecommunication Netwo
35、rk ICS Implementation Conformance Statement IP Internet Protocol PINX Private Integrated services Network eXchange PISN Private Integrated Services Network SS-CC Supplementary Service Call Completion (either SS-CCBS or SS-CCNR) SS-CCBS Supplementary Service Completion of Calls to Busy Subscribers SS
36、-CCNR Supplementary Service Completion of Calls on No Reply 6 Service architecture 6.1 Service architecture for invocation and operation 6.1.1 ECMA-186 service architecture The QSIG protocol for call completion invocation and operation is based around two signalling entities or PINX types: entity A
37、the PINX serving the calling user (user A); entity B the PINX serving the called user (user B). Where a user is in another network, the role of entity A or entity B is performed by the other network, the gateway or the two in combination. However, from the QSIG point of view the role is performed by
38、 the gateway, which acts as a gateway PINX. This can be represented diagrammatically as shown in figure 1. Entity AEntity BLeg AFigure 1 Call completion architecture From this it can be seen that there is only one segment or “leg” as far as the QSIG protocol is concerned (regardless of any transit e
39、ntities through which the signalling may pass). However, an instance of SS-CC consists of several consecutive phases, each phase being a separate instance of call related or call independent signalling. In other words, leg A in figure 1 represents several calls or call independent signalling connect
40、ions between entities A and B, which all belong to a single instance of SS-CC but may take different routes through the network. The typical course of action for an instance of SS-CC is: Prerequisite: unsuccessful call attempt because of busy or absent user B; invocation of SS-CC, using a call indep
41、endent signalling connection (signalling phase 1); monitoring of user B; there is no (network) signalling involved during this phase; - 4 - user B available notification, using call independent signalling, and suspension/resumption of SS-CC if user A is busy at this stage (signalling phase 2); recal
42、l, resulting in an automatically initiated basic call from user A to user B (signalling phase 3); cancellation of SS-CC, by the network (e.g. after timeout), or by user A or user B at any time (signalling phase 4). NOTE Interworking is only concerned with the phases that involve (network) signalling
43、. 6.1.2 H.450.9 service architecture The architecture shown above for QSIG applies also to H.450.9, except that PINXs are replaced by H.323 entities as follows: entity A the calling endpoint; entity B the called endpoint. Either entity can alternatively be located at a gatekeeper or proxy (as define
44、d in H.450.9) acting on behalf of the respective endpoint, the signalling between endpoint and gatekeeper/proxy being outside the scope of H.450.9. In this case the gatekeeper/proxy performs the role of entity A or B, respectively. However, from the H.450.9 point of view the role is performed by the
45、 endpoint. Where a user is in another network, the role of entity A or entity B is performed by the other network, the gateway or the two in combination. However, from the H.450.9 point of view the role is performed by the gateway. 6.1.3 Scenarios for interworking The architectures for ECMA-186 and
46、H.450.9 are very similar. This means that the same architecture is applicable to the inter-networking situation between an IP network and a PISN, where one user involved is served by the IP network and the other is served by the PISN. For the point of interworking, two scenarios arise, depending on
47、which side of the interworking point the PISN lies: Scenario A1: Entity A (PINX A) in PISN, entity B (endpoint B) in IP network; Scenario A2: Entity A (endpoint A) in IP network, entity B (PINX B) in PISN. The point of interworking will be implemented in a gateway, which acts as both an H.323 endpoi
48、nt from the point of view of the IP network and a gateway PINX from the point of view of the PISN. 6.1.4 Selection of the same gateway for all phases Since the different phases of an SS-CC instance in general use separate signalling paths, messages belonging to different phases may pass through diff
49、erent gateways. In this situation it does not make sense for a gateway to maintain SS-CC related states on either side, unless it can be assured that all signalling for a particular SS-CC instance passes through the same gateway. This is the case if there is only one gateway available for connecting the particular pair of users A and B at any time, but usually not if the load is shared dynamically between several gateways. One possible way to always choose the same gateway is by means of addressing. If the gateways themsel
