SIPCORE Working Group C. Holmberg Internet-Draft I. Sedlacek Intended status: Standards Track Ericsson Expires: March 28, 2011 September 24, 2010 Indication of features supported by proxy draft-holmberg-sipcore-proxy-feature-00.txt Abstract The Session Initiation Protocol (SIP) "Caller Preferences" extension defined in RFC 3840 provides a mechanism that allows a SIP message to convey information relating to the originator's capabilities. This document makes it possible for SIP proxies to convey similar information, by extending the rr-param rule defined in RFC 3261, so that the header field parameter can be used to convey feature tags that indicate features supported by the proxy. Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on March 28, 2011. Copyright Notice Copyright (c) 2010 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of Holmberg & Sedlacek Expires March 28, 2011 [Page 1] Internet-Draft proxy feature September 2010 the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Use-case: IMS Service Continuity . . . . . . . . . . . . . 3 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . 3 4. User Agent behavior . . . . . . . . . . . . . . . . . . . . . . 4 5. Proxy behavior . . . . . . . . . . . . . . . . . . . . . . . . 4 6. Feature tag semantics . . . . . . . . . . . . . . . . . . . . . 4 7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 7.1. Example name . . . . . . . . . . . . . . . . . . . . . . . 5 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5 9. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5 11. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 5 12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 12.1. Normative References . . . . . . . . . . . . . . . . . . . 6 12.2. Informative References . . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6 Holmberg & Sedlacek Expires March 28, 2011 [Page 2] Internet-Draft proxy feature September 2010 1. Introduction The SIP "Caller Preferences" extension defined in RFC 3840 [RFC3840] provides a mechanism that allows a SIP message to convey information, using feature tags, relating to the originator's capabilities. Feature information can be useful for other SIP entities, that might trigger actions and enable functions based on features supported by other SIP entities. This document extends the rr-param rule defined in RFC 3261 [RFC3261], so that it can be used to convey feature tags indicating support of features in SIP proxies. The rr-param rule is used in the SIP Path, Route, Record-Route and Service-Route header fields. 1.1. Use-case: IMS Service Continuity The 3rd Generation Partnership Project (3GPP) defines a IP Multimedia Subsystem (IMS) Service Continuity mechanism [3GPP.23.237] for handover of Packet Switched (PS) sessions to Circuit Switched (CS). The handover can be performed by a Service Centralization and Continuity Application Server (SCC AS), or by a SCC AS together with an Access Transfer Control Function (ATCF), that acts as a SIP proxy. Delegating part of the session handover functionality to an ATCF provides advantages related to voice interruption during session handover etc, since it is located in the same network as the user. In order for a SCC AS to delegate part of the session handover functionality to an ATCF, when it receives a SIP REGISTER request, it needs to be informed whether there is a proxy that provides ATCF functionality in the registration path. 2. Conventions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14, RFC 2119 [RFC2119]. 3. Definitions The rr-param rule defined in RFC 3261 [RFC3261]: rr-param = generic-param is extended to: Holmberg & Sedlacek Expires March 28, 2011 [Page 3] Internet-Draft proxy feature September 2010 rr-param = generic-param / feature-param where feature-param is defined in Section 9 of RFC 3840 [RFC3840]. 4. User Agent behavior This specification does not specify any new User Agent behavior. 5. Proxy behavior When a proxy inserts a Path header field (during registration), a Service-Route header field (during registration) or a Record-Route header field (during a dialog establishment), it MAY insert a feature tag in the header field. If a feature tag is inserted in a Path or Service-Route header field during registration, the resource identified by the URI in the header field MUST provide support for the associated feature for all dialogs associated with the registration, until the registration is terminated or re-freshed. If a feature tag is inserted in a Record-Route header field during a dialog establishment, the resource identified by the URI in the header field MUST provide support for the associated feature until the dialog is terminated. 6. Feature tag semantics The feature tag in a header field constructed using rr-param rule indicates support of the feature in the resource identified by the URI in the header field. In order to insert a feature tag in a SIP header field constructed by using rr-param rule, the feature specification MUST specify the semantics of the feature tag when inserted in that specific header field. Unless the feature specification defines such semantics, a the feature tag MUST NOT be included in that specific header field. NOTE: If a route set is built using Path, Record-Route or Service- Route header fields, any inserted feature tag will be copied into the associated Route header fields, together with other header field parameters. This specification does not define any specific meaning of the feature tags present in Route header fields in such cases. Holmberg & Sedlacek Expires March 28, 2011 [Page 4] Internet-Draft proxy feature September 2010 7. Examples 7.1. Example name TBD Alice P1 REGISTRAR | | | |--- REGISTER-------------->| | | | | | |--- REGISTER-------------->| | | Path: P1;+g.3gpp.srvcc | | | | | | | | |<-- 200 OK ----------------| | | Path: P1;+g.3gpp.srvcc | | | Service-Route: REG | |<-- 200 OK ----------------| | | Path: P1;+g.3gpp.srvcc | | | Service-Route: REG | | | | | Figure 1: Example call flow 8. IANA Considerations TBD 9. Security Considerations Feature tags can provide sensitive information about a SIP entity. RFC 3840 cautions against providing sensitive information to another party. Once this information is given out, any use may be made of it. 10. Acknowledgements Thanks to Paul Kyzivat for his comments and guidance on the mailing list. 11. Change Log [RFC EDITOR NOTE: Please remove this section when publishing] Holmberg & Sedlacek Expires March 28, 2011 [Page 5] Internet-Draft proxy feature September 2010 Changes from draft-holmberg-sipcore-proxy-feature-00 o To be added when the -01 version is submitted 12. References 12.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP: Session Initiation Protocol", RFC 3261, June 2002. [RFC3840] Rosenberg, J., Schulzrinne, H., and P. Kyzivat, "Indicating User Agent Capabilities in the Session Initiation Protocol (SIP)", RFC 3840, August 2004. 12.2. Informative References [3GPP.23.237] 3GPP, "IP Multimedia Subsystem (IMS) Service Continuity; Stage 2", 3GPP TS 23.237 10.2.0, June 2010. Authors' Addresses Christer Holmberg Ericsson Hirsalantie 11 Jorvas 02420 Finland Email: christer.holmberg@ericsson.com Ivo Sedlacek Ericsson Scheelevaegen 19C Lund 22363 Sweden Email: ivo.sedlacek@ericsson.com Holmberg & Sedlacek Expires March 28, 2011 [Page 6]