The Session Initiation Protocol (SIP) "Replaces" Header
RFC 3891
Document | Type | RFC - Proposed Standard (September 2004; Errata) | |
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Authors | Rohan Mahy , Billy Biggs , Rick Dean | ||
Last updated | 2015-10-14 | ||
Stream | Internent Engineering Task Force (IETF) | ||
Formats | plain text html pdf htmlized (tools) htmlized bibtex | ||
Stream | WG state | (None) | |
Document shepherd | No shepherd assigned | ||
IESG | IESG state | RFC 3891 (Proposed Standard) | |
Action Holders |
(None)
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Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | Allison Mankin | ||
Send notices to | (None) |
Network Working Group R. Mahy Request for Comments: 3891 Cisco Systems, Inc. Category: Standards Track B. Biggs R. Dean September 2004 The Session Initiation Protocol (SIP) "Replaces" Header 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. Copyright Notice Copyright (C) The Internet Society (2004). Abstract This document defines a new header for use with Session Initiation Protocol (SIP) multi-party applications and call control. The Replaces header is used to logically replace an existing SIP dialog with a new SIP dialog. This primitive can be used to enable a variety of features, for example: "Attended Transfer" and "Call Pickup". Note that the definition of these example features is non- normative. Mahy, et al. Standards Track [Page 1] RFC 3891 The SIP "Replaces" Header September 2004 Table of Contents 1. Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. User Agent Server Behavior: Receiving a Replaces Header . . . 4 4. User Agent Client Behavior: Sending a Replaces Header . . . . 6 5. Proxy Behavior. . . . . . . . . . . . . . . . . . . . . . . . 7 6. Syntax. . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 6.1. The Replaces Header . . . . . . . . . . . . . . . . . . 7 6.2. New Option Tag for Require and Supported Headers. . . . 8 7. Usage Examples. . . . . . . . . . . . . . . . . . . . . . . . 9 7.1. Replacing an Early Dialog at the Originator . . . . . . 9 8. Security Considerations . . . . . . . . . . . . . . . . . . . 11 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 9.1. Registration of "Replaces" SIP Header . . . . . . . . . 13 9.2. Registration of "replaces" SIP Option-tag . . . . . . . 13 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 13 11. References. . . . . . . . . . . . . . . . . . . . . . . . . . 13 11.1. Normative References. . . . . . . . . . . . . . . . . . 13 11.2. Informative References. . . . . . . . . . . . . . . . . 14 12. Authors' Addresses. . . . . . . . . . . . . . . . . . . . . . 15 13. Full Copyright Statement. . . . . . . . . . . . . . . . . . . 16 1. Overview This document describes a SIP [1] extension header field as part of the SIP multiparty applications architecture framework [10]. The Replaces header is used to logically replace an existing SIP dialog with a new SIP dialog. This is especially useful in peer-to-peer call control environments. One use of the "Replaces" header is to replace one participant with another in a multimedia conversation. While this functionality is already available using 3rd party call control [11] style call control, the 3pcc model requires a central point of control which may not be desirable in many environments. As such, a method of performing these same call control primitives in a distributed, peer-to-peer fashion is very desirable. Use of a new INVITE with a new header for dialog matching was chosen over making implicit associations in an incoming INVITE based on call-id or other fields for the following reasons: o An INVITE already has the correct semantics for a new call o Using an explicit Replaces header in a new request makes the intent of the request obvious. Mahy, et al. Standards Track [Page 2] RFC 3891 The SIP "Replaces" Header September 2004 o A unique call-id may be given to the replacement call. This avoids dialog matching problems in any of the related User Agents. o There are no adverse effects if the header is unsupported. The Replaces header enables services such as attended call transfer, retrieve from park, and transition from locally mixed conferences to two party calls in a distributed peer-to-peer way. This list of services is not exhaustive. Although the Replaces header is frequently used in combination with the REFER [8] method as used in a Transfer [12], they may be used independently. For example, Alice is talking to Bob from phone1. She transfers Bob to a Parking Place while she goes to the lab. When she gets thereShow full document text