Suppression of Session Initiation Protocol (SIP) REFER Method Implicit Subscription
RFC 4488

Approval announcement
Draft of message to be sent after approval:

From: The IESG <iesg-secretary@ietf.org>
To: IETF-Announce <ietf-announce@ietf.org>
Cc: Internet Architecture Board <iab@iab.org>,
    RFC Editor <rfc-editor@rfc-editor.org>, 
    sip mailing list <sip@ietf.org>, 
    sip chair <sip-chairs@tools.ietf.org>
Subject: Protocol Action: 'Suppression of Session Initiation 
         Protocol REFER Method Implicit Subscription' to Proposed 
         Standard 

The IESG has approved the following document:

- 'Suppression of Session Initiation Protocol REFER Method Implicit 
   Subscription '
   <draft-ietf-sip-refer-with-norefersub-05.txt> as a Proposed Standard

This document is the product of the Session Initiation Protocol Working 
Group. 

The IESG contact persons are Allison Mankin and Jon Peterson.

A URL of this Internet-Draft is:
http://www.ietf.org/internet-drafts/draft-ietf-sip-refer-with-norefersub-05.txt

Technical Summary
 
The SIP REFER extension as defined in RFC 3515 automatically
establishes a short-lived event subscription used to notify the 
party sending the REFER request about the execution of that request.
This notification is not needed in all cases.  This specification
provides a way to prevent this subscription/notification sequence,
using a new SIP extension header field which may be included in a
REFER request. A new sip option tag is also defined to provide for
declaration and discovery of support for this extension.
 
Working Group Summary

This specification was produced by the SIP working group in response
to requirements forwarded by the SIPPING working group and based in
part on requirements submitted by external organizations including
the Open Mobile Alliance. The draft iterated several times as an
individual draft before being adopted by the working group and added
to the charter.  Working group discussion centered on one key issue:
What sort of SIP extension mechanism, including URI, header field,
body part, or request type should be used to meet the requirements? A
breakout session during IETF 63 resulted in the compromise documented
in this specification, and subsequent working group review revealed a
very high level of consensus for the direction selected. Several
minor items, primarily typographical, were corrected during an
extended working group last call.

Protocol Quality
 
There no implementations of this extension known to the WG Chairs at the
time of publication request. However, we expect to see the extension
broadly used in mobile phones implementing the Open Mobile Alliance's
specification for Push to Talk Over Cellular.  

Dean Willis is the WG Chair shepherd.  Allison Mankin is the
Responsible Area Director.
 

Notes to RFC Editor
 
[replace the present abstract]

Abstract

OLD:
 This specification defines a way to suppress an implicit subscription
 with the Session Initiation Protocol (SIP) REFER method.  A new SIP
 option tag "norefersub" is defined to indicate support for this
 extension.  A new SIP header field "Refer-Sub" is defined to request
 the usage of this extension.

NEW:
The SIP REFER extension as defined in RFC 3515 automatically
establishes a short-lived event subscription used to notify the 
party sending the REFER request about the execution of that request.
This notification is not needed in all cases.  This specification
provides a way to prevent this subscription/notification sequence,
using a new SIP extension header field which may be included in a
REFER request. A new sip option tag is also defined to provide for
declaration and discovery of support for this extension.

------

Please expand the first use of User Agent (UA) and 
URI (Uniform Resource Identifier)

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Section 7 IANA Considerations

OLD:
The following information to be added to the header 
field sub-registry under 
http://www.iana.org/assignments/sip-parameters:

NEW:
The following information is added to the SIP
Header field sub-registry in the SIP Parameters Registry.

OLD:
This document also registers a new SIP option tag, "norefersub".

NEW:
This document also registers a new SIP option tag, "norefersub"
adding it to the SIP Option Tags sub-registry in the SIP 
Parameters Registry.

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Note to IANA

IANA - please note that the edits above are not new instruction,
but clearer information on where the registry objects go.