Clarifications for the Use of REFER with RFC 6665
RFC 7647


Document	Type	RFC - Proposed Standard (September 2015; No errata) Updates RFC 3515 Was draft-ietf-sipcore-refer-clarifications (sipcore WG)
	Last updated	2015-10-14
	Replaces	draft-sparks-sipcore-refer-clarifications
	Stream	IETF
	Formats	plain text pdf html bibtex
Stream	WG state	Submitted to IESG for Publication
	Document shepherd	Paul Kyzivat
	Shepherd write-up	Show (last changed 2015-04-29)
IESG	IESG state	RFC 7647 (Proposed Standard)
	Consensus Boilerplate	Yes
	Telechat date
	Responsible AD	Ben Campbell
	Send notices to	(None)
IANA	IANA review state	IANA OK - No Actions Needed
	IANA action state	No IC

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Internet Engineering Task Force (IETF)                         R. Sparks
Request for Comments: 7647                                        Oracle
Updates: 3515                                                 A.B. Roach
Category: Standards Track                                        Mozilla
ISSN: 2070-1721                                           September 2015

           Clarifications for the Use of REFER with RFC 6665

Abstract

   The SIP REFER method relies on the SIP-Specific Event Notification
   framework.  That framework was revised by RFC 6665.  This document
   highlights the implications of the requirement changes in RFC 6665,
   and updates the definition of the REFER method described in RFC 3515
   to clarify and disambiguate the impact of those changes.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7647.

Copyright Notice

   Copyright (c) 2015 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.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Sparks & Roach               Standards Track                    [Page 1]
RFC 7647                  Refer Clarifications            September 2015

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions Used in This Document . . . . . . . . . . . . . .   2
   3.  Use of GRUU Is Mandatory  . . . . . . . . . . . . . . . . . .   3
   4.  Dialog Reuse Is Prohibited  . . . . . . . . . . . . . . . . .   3
   5.  The 202 Response Code Is Deprecated . . . . . . . . . . . . .   4
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   The SIP REFER method relies on the SIP-Specific Event Notification
   framework.  That framework was revised by [RFC6665].  This document
   highlights the implications of the requirement changes in RFC 6665,
   and updates [RFC3515] to clarify and disambiguate the impact of those
   changes.

   Accepting a REFER request (without invoking extensions) results in an
   implicit SIP-Events subscription.  If that REFER was part of an
   existing dialog, the implicit subscription creates a new, problematic
   dialog usage within that dialog [RFC5057].  The "norefersub"
   extension defined in [RFC4488] asks to suppress this implicit
   subscription, but cannot prevent its creation.

   There are implementations in some known specialized environments
   (such as 3GPP) that use out-of-signaling agreements to ensure that
   in-dialog REFER requests using the RFC 4488 extension do not create a
   new subscription inside that dialog.  In the 3GPP environment, the
   behavior is based on capabilities advertised using media feature
   tags.  That mechanism does not, however, prevent additional dialog
   usages when interoperating with implementations that do not support
   the mechanism.  The extensions in [RFC7614] provide a standardized
   mechanism that allows avoiding any additional dialog usage.

2.  Conventions Used in This Document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

Sparks & Roach               Standards Track                    [Page 2]

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Clarifications for the Use of REFER with RFC 6665RFC 7647

Clarifications for the Use of REFER with RFC 6665
RFC 7647