The Session Initiation Protocol (SIP) Conference Bridge Transcoding Model
RFC 5370
Document | Type | RFC - Proposed Standard (October 2008; No errata) | |
---|---|---|---|
Author | Gonzalo Camarillo | ||
Last updated | 2015-10-14 | ||
Stream | Internent Engineering Task Force (IETF) | ||
Formats | plain text html pdf htmlized (tools) htmlized bibtex | ||
Reviews | |||
Stream | WG state | (None) | |
Document shepherd | No shepherd assigned | ||
IESG | IESG state | RFC 5370 (Proposed Standard) | |
Action Holders |
(None)
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||
Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | Jon Peterson | ||
Send notices to | (None) |
Network Working Group G. Camarillo Request for Comments: 5370 Ericsson Category: Standards Track October 2008 The Session Initiation Protocol (SIP) Conference Bridge Transcoding Model Status of This Memo This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited. Abstract This document describes how to invoke transcoding services using the conference bridge model. This way of invocation meets the requirements for SIP regarding transcoding services invocation to support deaf, hard of hearing, and speech-impaired individuals. Table of Contents 1. Introduction ....................................................2 2. Terminology .....................................................3 3. Caller's Invocation .............................................3 3.1. Procedures at the User Agent ...............................3 3.2. Procedures at the Transcoder ...............................3 3.3. Example ....................................................4 3.4. Unsuccessful Session Establishment .........................6 4. Callee's Invocation .............................................7 5. Security Considerations .........................................7 6. Contributors ....................................................8 7. References ......................................................8 7.1. Normative References .......................................8 7.2. Informative References .....................................9 Camarillo Standards Track [Page 1] RFC 5370 Conference Transcoding Model October 2008 1. Introduction RFC 5369 [RFC5369] describes how two SIP [RFC3261] UAs (User Agents) can discover incompatibilities that prevent them from establishing a session (e.g., lack of support for a common codec or for a common media type). When such incompatibilities are found, the UAs need to invoke transcoding services to successfully establish the session. The transcoding framework introduces two models to invoke transcoding services: the 3pcc (third-party call control) model [RFC4117] and the conference bridge model. This document specifies the conference bridge model. In the conference bridge model for transcoding invocation, a transcoding server that provides a particular transcoding service (e.g., speech-to-text) behaves as a B2BUA (Back-to-Back User Agent) between both UAs and is identified by a URI. As shown in Figure 1, both UAs, A and B, exchange signalling and media with the transcoder T. The UAs do not exchange any traffic (signalling or media) directly between them. +-------+ | |** | T | ** | |\ ** +-------+ \\ ** ^ * \\ ** | * \\ ** | * SIP ** SIP * \\ ** | * \\ ** | * \\ ** v * \ ** +-------+ +-------+ | | | | | A | | B | | | | | +-------+ +-------+ <-SIP-> Signalling ******* Media Figure 1: Conference bridge model Sections 3 and 4 specify how the caller A or the callee B, respectively, can use the conference bridge model to invoke transcoding services from T. Camarillo Standards Track [Page 2] RFC 5370 Conference Transcoding Model October 2008 2. Terminology In this document, the key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as described in BCP 14, RFC 2119 [RFC2119], and indicate requirement levels for compliant implementations. 3. Caller's Invocation User agent A needs to perform two operations to invoke transcoding services from T for a session between user agent A and user agent B. User agent A needs to establish a session with T and provide T with user agent B's URI so that T can generate an INVITE towards user agent B. 3.1. Procedures at the User AgentShow full document text