Requesting Answering Modes for the Session Initiation Protocol (SIP)
RFC 5373
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RFC - Proposed Standard
(November 2008; No errata)
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2015-10-14
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draft-willis-sip-answeralert
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IETF
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plain text
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IESG state |
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RFC 5373 (Proposed Standard)
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Consensus Boilerplate |
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Responsible AD |
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Cullen Jennings
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Network Working Group D. Willis, Ed.
Request for Comments: 5373 Softarmor Systems
Category: Standards Track A. Allen
Research in Motion (RIM)
November 2008
Requesting Answering Modes for the Session Initiation Protocol (SIP)
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" (STD1) for the standardization state and
status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (c) 2008 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.
Abstract
This document extends SIP with two header fields and associated
option tags that can be used in INVITE requests to convey the
requester's preference for user-interface handling related to
answering of that request. The first header, "Answer-Mode",
expresses a preference as to whether the target node's user interface
waits for user input before accepting the request or, instead,
accepts the request without waiting on user input. The second
header, "Priv-Answer-Mode", is similar to the first, except that it
requests administrative-level access and has consequent additional
authentication and authorization requirements. These behaviors have
applicability to applications such as push-to-talk and to diagnostics
like loop-back. Usage of each header field in a response to indicate
how the request was handled is also defined.
Willis & Allen Standards Track [Page 1]
RFC 5373 SIP Answering Modes November 2008
Table of Contents
1. Background . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 5
2. Syntax of Header Fields and Option Tags . . . . . . . . . . . 5
3. Usage of the Answer-Mode and Priv-Answer-Mode Header Fields . 6
4. Usage of the Answer-Mode and Priv-Answer-Mode Header
Fields in Requests . . . . . . . . . . . . . . . . . . . . . . 6
4.1. The Difference Between Answer-Mode and Priv-Answer-Mode . 7
4.2. The "require" Modifier . . . . . . . . . . . . . . . . . . 9
4.3. Procedures at User Agent Clients (UAC) . . . . . . . . . . 9
4.3.1. All Requests . . . . . . . . . . . . . . . . . . . . . 9
4.3.2. REGISTER Transactions . . . . . . . . . . . . . . . . 9
4.3.3. INVITE Transactions . . . . . . . . . . . . . . . . . 10
4.4. Procedures at Intermediate Proxies . . . . . . . . . . . . 12
4.4.1. General Proxy Behavior . . . . . . . . . . . . . . . . 12
4.4.2. Issues with Automatic Answering and Forking . . . . . 12
4.5. Procedures at User Agent Servers (UAS) . . . . . . . . . . 13
4.5.1. INVITE Transactions . . . . . . . . . . . . . . . . . 13
5. Usage of the Answer-Mode and Priv-Answer-Mode Header
Fields in Responses . . . . . . . . . . . . . . . . . . . . . 14
5.1. Procedures at the UAS . . . . . . . . . . . . . . . . . . 14
5.2. Procedures at the UAC . . . . . . . . . . . . . . . . . . 15
6. Examples of Usage . . . . . . . . . . . . . . . . . . . . . . 15
6.1. REGISTER Request . . . . . . . . . . . . . . . . . . . . . 15
6.2. INVITE Request . . . . . . . . . . . . . . . . . . . . . . 16
6.3. 200 (OK) Response . . . . . . . . . . . . . . . . . . . . 16
7. Security Considerations . . . . . . . . . . . . . . . . . . . 16
7.1. Attack Sensitivity Depends on Media Characteristics . . . 17
7.2. Application Design Affects Attack Opportunity . . . . . . 19
7.3. Applying the Analysis . . . . . . . . . . . . . . . . . . 19
7.4. Minimal Policy Requirement . . . . . . . . . . . . . . . . 21
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22
8.1. Registration of Header Fields . . . . . . . . . . . . . . 22
8.2. Registration of Header Field Parameters . . . . . . . . . 22
8.3. Registration of SIP Option Tags . . . . . . . . . . . . . 22
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 23
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