An Extension to Session Initiation Protocol (SIP) Events for Conditional Event Notification
RFC 5839

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>, 
    sipcore mailing list <sipcore@ietf.org>, 
    sipcore chair <sipcore-chairs@tools.ietf.org>
Subject: Protocol Action: 'An Extension to Session Initiation Protocol
(SIP) Events for Conditional Event Notification' to Proposed Standard

The IESG has approved the following document:

- 'An Extension to Session Initiation Protocol (SIP) Events 
   for Conditional Event Notification '
   <draft-ietf-sipcore-subnot-etags-04.txt> as a Proposed Standard


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

The IESG contact persons are Robert Sparks and Cullen Jennings.

A URL of this Internet-Draft is:
http://www.ietf.org/internet-drafts/draft-ietf-sipcore-subnot-etags-04.txt

Technical Summary

  The Session Initiation Protocol (SIP) events framework enables
  receiving asynchronous notification of various events from other SIP
  user agents. This framework defines the procedures for creating,
  refreshing and terminating subscriptions, as well as fetching and
  periodic polling of resource state. These SIP Events Framework
  procedures have a serious deficiency in that they provide no tools to
  avoid replaying event notifications that have already been received by
  a user agent. This specification defines an extension to SIP events
  that allows the subscriber to condition the subscription request to
  whether the state has changed since the previous notification was
  received. When such a condition is true, either the body of a
  resulting event notification or the entire notification message is
  suppressed. This "conditioning" of the subscription requests uses the
  well-known concept of entity tags (eTags).

Working Group Summary

  This document received extended working group review during a SIP WGLC
  period that exceeded one year in duration. One critical clarification
  came up in this review period: this specification does not provide
  "versioning history" for events; rather it lets a subscriber know
  whether the current event state is consistent with the event state as
  currently known by that subscriber. The distinction is subtle. For
  example, if the subscriber knows of event state "A", but the actual
  state has changed to "B" and then back to "A" before a NOTIFY would
  be sent (if the subscriber were offline for example), the subscriber
  will not be informed about the B state through this specification.

  Following WGLC, the proto review process detected and corrected a
  minor error in the ABNF, and further review by Adam Roach detected and
  corrected problem related to suppressed NOTIFYs on initial dialogs.

Document Quality

  The Open Mobile Alliance SIMPLE Presence specification references this
  document, and has done so for several years.

Personnel

  Dean Willis is this document's shepherd.
  Robert Sparks is the responsible AD.