1、 ECMA-361 1stEdition / December 2004 Corporate Telecommunication Networks - Signalling Interworking between QSIG and SIP - Call Transfer Standard ECMA-361 1stEdition / December 2004 Corporate Telecommunication Networks - Signalling Interworking between QSIG and SIP - Call Transfer Ecma International
2、 Rue du Rhne 114 CH-1204 Geneva T/F: +41 22 849 6000/01 www.ecma-international.org IW Ecma-361.doc 14.12.2004 11:49 . 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)
3、 (also known as enterprise networks). 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. It has been produced under ETSI work item DTS/ECMA-00297. This Standard specifies cal
4、l transfer interworking between the Session Initiation Protocol (SIP) and QSIG within corporate telecommunication networks (also known as enterprise networks). SIP is an Internet application-layer control (signalling) protocol for creating, modifying, and terminating sessions with one or more partic
5、ipants. These sessions include, in particular, telephone calls. 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, IETF, ETSI and other international and national standardizati
6、on bodies. It represents a pragmatic and widely based consensus. This Ecma Standard has been adopted by the General Assembly of December 2004. Table of contents1 Scope 1 2 References 1 3 Terminology 2 4 Definitions 3 4.1 External definitions 3 4.2 Other definitions 3 4.2.1 User A 3 4.2.2 User B 3 4.
7、2.3 User C 3 4.2.4 Call transfer 3 4.2.5 Single step call transfer 4.2.6 Call transfer by join 4.2.7 Call transfer by rerouteing 4.2.8 Corporate telecommunication Network (CN) 4.2.9 IP network 3 4.2.10 Private Integrated Services Network (PISN) 4 4.2.11 Private Integrated services Network eXchange (
8、PINX) 5 Abbreviations and acronyms 6 Background and architecture 7 Procedures 4 7.1 Call transfers in QSIG 7.2 Call transfer in SIP 5 7.3 Scope of the interworking functions 7.3.1 QSIG side 5 7.3.2 SIP side 5 7.3.3 Discussion over transfer interworking functions 7.4 Mapping of numbers and URIs 8 7.5
9、 UAC Processing 8 7.5.1 Receipt of a FACILITY message with callTransferComplete invoke APDU 8 7.5.2 Receipt of a FACILITY message with callTransferUpdate invoke APDU 9 7.5.3 Receipt of a FACILITY message with ssctInitiate invoke APDU 9 7.5.4 Receipt of a SETUP message with ssctSetup invoke APDU 10 7
10、.5.5 Receipt of a FACILITY message with subaddressTransfer invoke APDU 11 7.6 UAS Processing 11 7.6.1 Receipt of a SIP REFER request 11 - i - 7.6.2 Receipt of a SIP INVITE request 16 7.6.3 Receipt of a SIP request with revised identity 17 8 Example message sequences 18 8.1 Call transfer by join wher
11、e User B and C are SIP participants 18 8.2 Call transfer where User A is a SIP participant 19 8.3 Call transfer where User A is a SIP participant and where two gateways are used 20 8.4 Call transfer where User A and User B are SIP participants 21 8.5 Single step call transfer where User B is a SIP p
12、articipant 22 8.6 Unsuccessful Single step call transfer where User A and User C are SIP participants 23 8.7 Single step call transfer where User A and User B are SIP participants 24 9 Security considerations 24 - ii - 1 Scope This Standard specifies call transfer interworking between the Session In
13、itiation Protocol (SIP) and “QSIG” within corporate telecommunication networks (CN), also known as enterprise networks. “QSIG“ is a signalling protocol that operates between Private Integrated services Network eXchanges (PINX) within a Private Integrated Services Network (PISN). A PISN provides circ
14、uit-switched basic services and supplementary services to its users. QSIG is specified in Ecma Standards, in particular 1 (call control in support of basic services), 2 (generic functional protocol for the support of supplementary services) and a number of Standards specifying individual supplementa
15、ry services. Transfer services are specified in 3, 6 and the QSIG signalling protocol in support of these services is specified in 4, 7. In particular, this signalling protocol signals information about call transfer to the users who are involved. NOTE The name QSIG was derived from the fact that it
16、 is used for signalling at the Q reference point. The Q reference point is a point of demarcation between two PINXs. SIP is an application layer protocol for establishing, terminating and modifying multimedia sessions. It is typically carried over IP. Telephone calls are considered as a type of mult
17、imedia session where just audio is exchanged. SIP is defined in 10. As the support of telephony within corporate networks evolves from circuit-switched technology to Internet technology, the two technologies will co-exist in many networks for a period, perhaps several years. Therefore there is a nee
18、d to be able to establish, modify, terminate and transfer sessions involving participants in the SIP network and participants in the QSIG network. Such calls are supported by gateways that perform interworking between SIP and QSIG. This specification specifies SIP-QSIG signalling interworking for tr
19、ansfer services between a PISN employing QSIG and a corporate IP network employing SIP. 2 References 1 International Standard ISO/IEC 11572 “Information technology - Telecommunications and information exchange between systems - Private Integrated Services Network - Circuit mode bearer services - Int
20、er-exchange signalling procedures and protocol“ (also published by Ecma as Standard ECMA-143). 2 International Standard ISO/IEC 11582 “Information technology - Telecommunications and information exchange between systems - Private Integrated Services Network - Generic functional protocol for the supp
21、ort of supplementary services - Inter-exchange signalling procedures and protocol “ (also published by Ecma as Standard ECMA-165). 3 International Standard ISO/IEC 13865 “Information technology - Telecommunications and information exchange between systems - Private Integrated Services Network - Spec
22、ification, functional model and information flows - Call Transfer supplementary service“ (also published by Ecma as Standard ECMA-177). 4 International Standard ISO/IEC 13869 “Information technology - Telecommunications and information exchange between systems - Private Integrated Services Network -
23、 Inter-exchange signalling protocol - Call Transfer supplementary service“ (also published by Ecma as Standard ECMA-178). 5 International Standard ISO/IEC 17343 “Information technology - Telecommunications and information exchange between systems - Corporate telecommunication networks - Signalling i
24、nterworking between QSIG and SIP - Basic services“ (also published by Ecma as Standard ECMA-339). 6 International Standard ISO/IEC 19459 “Information technology - Telecommunications and information exchange between systems - Private Integrated Services Network - Specification, functional model and i
25、nformation flows - Single Step Call Transfer Supplementary Service“ (also published by Ecma as Standard ECMA-299). - 1 - 7 International Standard ISO/IEC 19460 “Information technology - Telecommunications and information exchange between systems - Private Integrated Services Network - Inter-exchange
26、 signalling protocol - Single Step Call Transfer supplementary service“ (also published by Ecma as Standard ECMA-300). 8 Ecma Technical Report TR/86, “Corporate Telecommunication Networks User Identification in a SIP/QSIG Environment“. 9 Bradner, S., “Key words for use in RFCs to Indicate Requiremen
27、t Levels“, BCP 14, RFC 2119. 10 J. Rosenberg, H. Schulzrinne, et al., “SIP: Session initiation protocol“, RFC 3261. 11 J. Peterson, “A Privacy Mechanism for the Session Initiation Protocol (SIP)“, RFC 3323. 12 R. Sparks, “The Session Initiation Protocol (SIP) REFER Method“, RFC 3515. 13 R. Mahy, B.
28、Biggs, R. Dean, “The Session Initiation Protocol (SIP) “Replaces“ Header“, RFC 3891. 14 R. Sparks, “The Session Initiation Protocol (SIP) Referred-By Mechanism“, RFC 3892. 15 R. Sparks, A. Johnston, “Session Initiation Protocol Call Control - Transfer“, draft-ietf-sipping-cc-transfer-02 (work in pro
29、gress). 3 Terminology In this document, the key words “MUST“, “MUST NOT“, “REQUIRED“, “SHALL“, “SHALL NOT“, “SHOULD“, “SHOULD NOT“, “RECOMMENDED“, “MAY“, and “OPTIONAL“ are to be interpreted as described in RFC 2119 9 and indicate requirement levels for compliant SIP implementations. In the interest
30、s of keeping the normative text and the diagrams as simple as possible, the QSIG messages in this document implicitly follow QSIG signalling rules of 1 and 2. For instance, sending a QSIG DISCONNECT message on a call where a QSIG DISCONNECT has already been sent is implicitly forbidden and therefore
31、 not mentioned as such in this document. The figures in this document are provided as examples. They are not normative. In the interests of keeping the diagrams simple, some SIP messages (ACK, PRACK, final responses to BYE and NOTIFY) are not shown. The following notation is used for call transfer i
32、nformation within QSIG messages: xxx.inv - invoke application protocol data unit (APDU) of operation xxx. xxx.res - return result APDU of operation xxx. xxx.err - return error APDU of operation xxx. The following abbreviations are used: ctActive stands for callTransferActive. ctComplete stands for c
33、allTransferComplete. The drawings use the following conventions: D1 and D2 are SIP dialogs. CR1 and CR2 are QSIG call references. By convention, D1 is mapped to CR1 and D2 to CR2. A SIP message is prefixed by (Dx-y), when it belongs to SIP dialog Dx and is part of SIP transaction y. The method or re
34、sponse code of the SIP messages is displayed, as well as the name of SIP header fields that play a role in the interworking functions. Some examples display an “Identity:“ information field. It indicates that the local identity information field should be mapped to a real SIP identity information fi
35、eld as described in 7.4. - 2 - 4 Definitions For the purposes of this specification, the following definitions apply. 4.1 External definitions The definitions in 1 and 10 apply as appropriate. 4.2 Other definitions 4.2.1 User A The served user, i.e. the user requesting Call transfer or Single step c
36、all transfer. 4.2.2 User B A user who is in communication with User A and who will be transferred to User C. NOTE This definitions differs from 3, in order to use similar conventions for QSIG Call transfer and QSIG Single step call transfer. 4.2.3 User C The user to whom the call is transferred. 4.2
37、.4 Call transfer The act of enabling a user (User A) to transform two of that users calls (at least one of which must be answered) into a new call between the two other users (User B and User C) in the two calls. NOTE Call transfer is very similar to the “attended transfer“ described in 15. A Call t
38、ransfer before answer is a Call transfer that occurs before User C answers the call initiated by User A. 4.2.5 Single step call transfer The act of enabling a served user (User A) to transfer an active call (with User B) to a user (User C) that has no call established either to User A or to User B.
39、On successful completion of Single step call transfer, User B and User C can communicate with each other and User A are no longer involved in a call with User B or User C. NOTE Single step call transfer is very similar to the “basic transfer“ described in 15. 4.2.6 Call transfer by join The effectin
40、g of transfer when User A is a PISN user by joining together the connections of the calls to User B and User C at User As PINX. 4.2.7 Call transfer by rerouteing The effecting of transfer by establishing a new connection to replace all or part of the connections of the calls to User B and User C. 4.
41、2.8 Corporate telecommunication Network (CN) Sets of privately-owned or carrier-provided equipment that are located at geographically dispersed locations and are interconnected to provide telecommunication services to a defined group of users. NOTE 1 A CN can comprise a PISN, a private IP network (i
42、ntranet) or a combination of the two. NOTE 2 Also known as enterprise network. 4.2.9 IP network A network, unless otherwise stated a corporate network, offering connectionless packet-mode services based on the Internet Protocol (IP) as the network layer protocol. - 3 - 4.2.10 Private Integrated Serv
43、ices Network (PISN) A CN or part of a CN that employs circuit-switched technology and QSIG signalling. 4.2.11 Private Integrated services Network eXchange (PINX) A PISN nodal entity comprising switching and call handling functions and supporting QSIG signalling in accordance with 1. 5 Abbreviations
44、and acronyms APDU Application Protocol Data Unit IP Internet Protocol PINX Private Integrated services Network eXchange PISN Private Integrated Services Network SIP Session Initiation Protocol UA User Agent UAC User Agent Client UAS User Agent Server URI Universal Resource Identifier 6 Background an
45、d architecture The background and architecture of 5 applies. In addition, the interworking function in the protocol model handles interworking for call transfer services. This involves interworking between the QSIG call transfer protocol specified in 4, 7 and SIP 10, including the use of the REFER 1
46、2 SIP method and Replaces 13 and Referred-By 14 SIP header fields. 7 Procedures 7.1 Call transfers in QSIG For the purposes of QSIG, transfers are classified into one of the following types: call transfer by join: defined in 4.2.6; call transfer by rerouteing: defined in 4.2.7; and single step call
47、transfer: defined in 4.2.5. QSIG Call transfer by rerouteing is out of scope of this document because of its lesser deployment. QSIG signalling for transfers is based on 2 and comprises the following remote operations: ssctInitiate - this confirmed operation is sent by User As PINX to User Bs PINX.
48、It initiates a single step call transfer. It includes a “rerouteingNumber“ of User C. It also includes an optional “transferredAddress“ of User B, an optional “transferringAddress“ of User A, and a optional boolean “awaitConnect“ that indicates if the operation return result is expected when the cal
49、l is connected or when it is alerting User C. callTransferActive - this unconfirmed operation is sent to User B. It indicates that answer has taken place following a Call transfer before answer. It includes a “connectedAddress“ that identifies the other User that answered the transferred call. callTransferComplete - this unconfirmed operation is sent to User B and User C. It indicates that a transfer has been effected. It includes an indication of w
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