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

Document Type Replaced Internet-Draft (sip WG)
Last updated 2009-04-20 (latest revision 2008-07-14)
Replaces draft-niemi-sip-subnot-etags
Replaced by draft-ietf-sipcore-subnot-etags
Stream IETF
Intended RFC status (None)
Expired & archived
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Stream WG state WG Document
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IESG IESG state Replaced by draft-ietf-sipcore-subnot-etags
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This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at


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 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 memo 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.


Aki Niemi (

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