Session Initiation Protocol (SIP) Call Control - Conferencing for User Agents
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From: The IESG <email@example.com> To: IETF-Announce <firstname.lastname@example.org> Cc: Internet Architecture Board <email@example.com>, RFC Editor <firstname.lastname@example.org>, sipping mailing list <email@example.com>, sipping chair <firstname.lastname@example.org> Subject: Protocol Action: 'Session Initiation Protocol Call Control - Conferencing for User Agents' to BCP The IESG has approved the following document: - 'Session Initiation Protocol Call Control - Conferencing for User Agents ' <draft-ietf-sipping-cc-conferencing-08.txt> as a BCP This document is the product of the Session Initiation Proposal Investigation Working Group. The IESG contact persons are Allison Mankin and Jon Peterson. A URL of this Internet-Draft is: http://www.ietf.org/internet-drafts/draft-ietf-sipping-cc-conferencing-08.txt
Technical Summary This specification defines conferencing call control features for the Session Initiation Protocol (SIP). This document builds on the Conferencing Requirements and Framework documents to define how a tightly coupled SIP conference works. The approach is explored from different user agent (UA) types perspective: conference-unaware, conference-aware and focus UAs. The use of URIs in conferencing, OPTIONS for capabilities discovery, and call control using REFER are covered in detail with example call flow diagrams. The usage of the isfocus feature tag is defined. This specification uses the concepts and definitions from the WG's "High Level Requirements for Tightly Coupled SIP Conferencing," and "A Framework for Conferencing with the Session Initiation Protocol," approved earlier. In the tightly coupled architecture, a UA, known as participant, establishes a SIP dialog with another UA, known as focus. The focus is the central point of control, authentication and authorization. This specification defines the operations of a focus and participant UAs. Not that only the signaling (SIP) needs to be centralized in this model - the media can be centrally mixed, distributed, or even multicast (by the nature of the media descriptions that the model establishes). For a full discussion of this architecture, see the SIP conferencing Framework mentioned already. already. This document presents the basic call control (dial-in and dial-out) conferencing building blocks from the UA perspective. Possible applications include ad-hoc conferences and scheduled conferences. Working Group Summary The working group strongly supported advancing this document. 3GPP and OMA have notified the IETF that this specification is a critical dependency. Protocol Quality Allison Mankin reviewed the specification for the IESG. It was revised to add specific security considerations. Due to a General Area Directorate Review, it was revised to add some additional context and introduction. Gonzalo Camarillo is the working group shepherd. Notes to the RFC Editor Section 3.1 Remove the sentence: "A focus SHOULD utilize a GRUU as discussed in Section 4.2." Section 4.2 OLD: The Conference URI MUST have the GRUU (Globally Routable User Agent URI) properties as detailed in . NEW: By their nature, the conferences supported by this specification are centralized. Therefore, typically a conferencing system needs to allocate a SIP Conference URI such that SIP requests to this URI are not forked and are routed to a dedicated conference focus. For example, for a globally accessible SIP conference could be well constructed with a Conference URI using a Globally Routable User Agent URI (GRUU) (defined in ), because of its ability to support the non-forking and global routability requirements.