Network Working Group Abhishek Gupta Internet-Draft Independent Consultant Intended status: Standards Track June 20, 2015 Expires: Dec 19, 2015 Conveying Event Tag with the Session Initiation Protocol REFER Method draft-abhishek-refer-to-event-parameter-01 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), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. 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." 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Abstract This document extends the REFER method, defined in RFC 3515, to convey feature parameters defined in RFC 3840. 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 [1]. To simplify discussions of the REFER method and its extensions, three new terms are used throughout the document: - REFER-Issuer: the UA issuing the REFER request - REFER-Recipient: the UA receiving the REFER request - REFER-Target: the UA designated in the Refer-To URI Introduction This document extends the SIP REFER method defined in RFC 3515 to be used with feature parameters defined in RFC 3840. Feature tags are used by a UA to convey to another UA information about capabilities and features. This information can be shared by a UA using a number of mechanisms, including OPTIONS responses. Feature tag information can be very useful to another UA. It is especially useful prior to the establishment of a subscription, triggered only through REFER method. This is valid only for the request containing parameter "method=SUBSCRIBE" in Refer-To header. While sending this request if there is no mechanism to indicate as to which event is to be subscribed, the REFER-Recipient may send SUBSCRIBE with an undesired event. For example, if a REFER-Issuer knows (through an OPTIONS query, for example) that the remote REFER-Target supports events like dialog the REFER-Recipient might subscribe with dialog or any other event as specified. This extension to the REFER method provides a mechanism by which the REFER-Issuer can provide this useful information about the REFER-Target capabilities and functionality to the REFER-Recipient by including feature tags in the Refer-To header field in a REFER request. Examples 1. The example below shows how the REFER-Issuer tells the REFER- Recipient that the REFER-Target supports dialog event package. Refer-To: ;events=dialog 2. In case the REFER-Recipient doesn't support the desired event in the Refer-To header, a 489 Bad Event will be responded to REFER request. Security Considerations Feature tags can provide sensitive information about a user or a UA. As such, RFC 3840 cautions against providing sensitive information to another party. Once this information is given out, any use may be made of it, including relaying to a third party as in this specification. A REFER-Issuer MUST NOT create or guess event tags - instead an event tag included in a REFER SHOULD have been discovered in an authenticated and secure method (such as an OPTIONS response) directly from the REFER-Target. It is RECOMMENDED that the REFER-Issuer includes in the Refer-To header field the desired feature tag that were listed in the most recent Allow-Events header of the REFER-Target. Normative References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [2] 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. [3] Sparks, R., "The Session Initiation Protocol (SIP) Refer Method", RFC 3515, April 2003. [4] Rosenberg, J., Schulzrinne, H., and P. Kyzivat, "Indicating User Agent Capabilities in the Session Initiation Protocol (SIP)", RFC 3840, August 2004. Authors' Addresses Abhishek Gupta Independent Consultant Navi Mumbai - 400701 India Mobile: +91-9930230341 Email: abhishek.sept@gmail.com