datatracker.ietf.org
Sign in
Version 5.6.3, 2014-09-19
Report a bug

Update to the Session Initiation Protocol (SIP) Preconditions Framework
RFC 4032

Document type: RFC - Proposed Standard (March 2005; No errata)
Updates RFC 3312
Document stream: IETF
Last updated: 2013-03-02
Other versions: plain text, pdf, html

IETF State: (None)
Consensus: Unknown
Document shepherd: No shepherd assigned

IESG State: RFC 4032 (Proposed Standard)
Responsible AD: Allison Mankin
Send notices to: dean.willis@softarmor.com, gonzalo.camarillo@ericsson.com, rohan@ekabal.com

Network Working Group                                       G. Camarillo
Request for Comments: 4032                                      Ericsson
Updates: 3312                                                 P. Kyzivat
Category: Standards Track                                  Cisco Systems
                                                              March 2005

            Update to the Session Initiation Protocol (SIP)
                        Preconditions Framework

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 (2005).

Abstract

   This document updates RFC 3312, which defines the framework for
   preconditions in SIP.  We provide guidelines for authors of new
   precondition types and describe how to use SIP preconditions in
   situations that involve session mobility.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  2
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  2
   3.  Defining New Precondition Types  . . . . . . . . . . . . . . .  3
       3.1.  Precondition Type Tag  . . . . . . . . . . . . . . . . .  3
       3.2.  Status Type  . . . . . . . . . . . . . . . . . . . . . .  3
       3.3.  Precondition Strength  . . . . . . . . . . . . . . . . .  3
       3.4.  Suspending and Resuming Session Establishment  . . . . .  3
   4.  Issues Related to Session Mobility . . . . . . . . . . . . . .  4
       4.1.  Update to RFC 3312 . . . . . . . . . . . . . . . . . . .  5
       4.2.  Desired Status . . . . . . . . . . . . . . . . . . . . .  7
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . .  7
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  7
   7.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .  8
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  8
       8.1.  Normative References . . . . . . . . . . . . . . . . . .  8

Camarillo & Kyzivat         Standards Track                     [Page 1]
RFC 4032              SIP Preconditions Framework             March 2005

       8.2.  Informational References . . . . . . . . . . . . . . . .  8
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . .  9
   Full Copyright Statement . . . . . . . . . . . . . . . . . . . . . 10

1.  Introduction

   RFC 3312 [3] defines the framework for SIP [2] preconditions, which
   is a generic framework that allows SIP UAs (User Agents) to suspend
   the establishment of a session until a set of preconditions are met.
   Although only Quality of Service (QoS) preconditions have been
   defined so far, this framework supports different types of
   preconditions.  (QoS preconditions are defined by RFC 3312 as well).

   This document updates RFC 3312,  provides guidelines for authors of
   new precondition types and explains which topics they need to discuss
   when defining them.  In addition, it updates some of the procedures
   in RFC 3312 for using SIP preconditions in situations that involve
   session mobility as described below.

   RFC 3312 focuses on media sessions that do not move around.  That is,
   media is sent between the same end-points throughout the duration of
   the session.  Nevertheless, media sessions established by SIP are not
   always static.

   SIP offers mechanisms to provide session mobility, namely re-INVITEs
   and UPDATEs [5].  While existing implementations of RFC 3312 can
   probably handle session mobility, there is a need to explicitly point
   out the issues involved and make a slight update on some of the
   procedures defined there in.  With the updated procedures defined in
   this document, messages carrying precondition information become more
   explicit about the current status of the preconditions.

   Specifically, we now allow answers to downgrade current status values
   (this was disallowed by RFC 3312).  We consider moving an existing
   stream to a new location as equivalent to establishing a new stream.
   Therefore, answers moving streams to new locations set all the
   current status values in their answers to "No" and start a new
   precondition negotiation from scratch.

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

[include full document text]