Network Working Group R. Sparks Internet-Draft Oracle Updates: 3515 (if approved) A. Roach Intended status: Standards Track Mozilla Expires: December 18, 2014 June 16, 2014 Clarifications for the use of REFER with RFC6665 draft-sparks-sipcore-refer-clarifications-00 Abstract An accepted SIP REFER method creates an implicit subscription using the SIP-Specific Event Notification Framework. That framework was revised by RFC6665. This document highlights the implications of the requirement changes in RFC6665, and updates the definition of the REFER method, RFC3515, to clarify and disambiguate the impact of those changes. Status of This Memo This Internet-Draft is submitted 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 December 18, 2014. Copyright Notice Copyright (c) 2014 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 Sparks & Roach Expires December 18, 2014 [Page 1]
Internet-Draft Refer Clarifications June 2014 the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Conventions and Definitions . . . . . . . . . . . . . . . . . 2 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 3. Use of GRUU is mandatory . . . . . . . . . . . . . . . . . . 2 4. Dialog reuse is prohibited . . . . . . . . . . . . . . . . . 3 5. Security Considerations . . . . . . . . . . . . . . . . . . . 3 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 3 7.1. Normative References . . . . . . . . . . . . . . . . . . 3 7.2. Informative References . . . . . . . . . . . . . . . . . 4 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 4 1. Conventions and Definitions 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 [RFC2119]. 2. Introduction An accepted SIP REFER method creates an implicit subscription using the SIP-Specific Event Notification Framework. That framework was revised by [RFC6665]. This document highlights the implications of the requirement changes in RFC6665, and updates [RFC3515] to clarify and disambiguate the impact of those changes. 3. Use of GRUU is mandatory Section 4.5.1 of [RFC6665] makes GRUU [RFC5627] mandatory to implement and use as the local target in the subscription created by the REFER request. A user agent constructing a REFER request MUST populate its Contact header field with a GRUU. As RFC6665 details, this is necessary to ensure that NOTIFY requests sent in the implicitly created subscription arrive at this user agent without creating a second usage inside an existing dialog. Using the "norefersub" option tag [RFC4488] does not change this requirement, even if used in a "Require" header field. Even if the recipient supports the "norefersub" mechanism, and accepts the request with the option tag in the "Require" header field, it is allowed to return a "Refer-Sub" header field with a value of "true" in the response, and create an implicit subscription. Sparks & Roach Expires December 18, 2014 [Page 2]
Internet-Draft Refer Clarifications June 2014 4. Dialog reuse is prohibited As a direct consequence of requiring the use of GRUU, and the requirements in section 4.5.2 of RFC6665, sending a REFER within any existing dialog is prohibited. A user agent constructing a REFER request MUST built it as an out-of- dialog message as defined in [RFC3261]. Thus, the REFER request will have no tag parameter in its To: header field. A user agent wishing to identify an existing dialog (such as for call transfer as defined in [RFC5589] MUST use the "Target-Dialog" extension defined in [RFC4538] to do so. 5. Security Considerations This document introduces no new security considerations directly. The updated considerations in [RFC6665] apply to the implicit subscription created by an accepted REFER request. 6. IANA Considerations This document has no actions for IANA. 7. References 7.1. 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. [RFC3515] Sparks, R., "The Session Initiation Protocol (SIP) Refer Method", RFC 3515, April 2003. [RFC4538] Rosenberg, J., "Request Authorization through Dialog Identification in the Session Initiation Protocol (SIP)", RFC 4538, June 2006. [RFC5627] Rosenberg, J., "Obtaining and Using Globally Routable User Agent URIs (GRUUs) in the Session Initiation Protocol (SIP)", RFC 5627, October 2009. Sparks & Roach Expires December 18, 2014 [Page 3]
Internet-Draft Refer Clarifications June 2014 [RFC6665] Roach, A., "SIP-Specific Event Notification", RFC 6665, July 2012. 7.2. Informative References [RFC4488] Levin, O., "Suppression of Session Initiation Protocol (SIP) REFER Method Implicit Subscription", RFC 4488, May 2006. [RFC5589] Sparks, R., Johnston, A., and D. Petrie, "Session Initiation Protocol (SIP) Call Control - Transfer", BCP 149, RFC 5589, June 2009. Authors' Addresses Robert Sparks Oracle 7460 Warren Parkway Suite 300 Frisco, Texas 75034 US Email: RjS@nostrum.com Adam Roach Mozilla Dallas, TX US Phone: +1 650 903 0800 x863 Email: adam@nostrum.com Sparks & Roach Expires December 18, 2014 [Page 4]