An Extension to Session Initiation Protocol (SIP) Events for Conditional Event Notification
RFC 5839
Internet Engineering Task Force (IETF) A. Niemi
Request for Comments: 5839 Nokia
Category: Standards Track D. Willis, Ed.
ISSN: 2070-1721 Softarmor Systems
May 2010
An Extension to Session Initiation Protocol (SIP) Events
for Conditional Event Notification
Abstract
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 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.
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/rfc5839.
Niemi & Willis Standards Track [Page 1]
RFC 5839 Entity-Tags for SIP Events May 2010
Copyright Notice
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Niemi & Willis Standards Track [Page 2]
RFC 5839 Entity-Tags for SIP Events May 2010
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Document Conventions . . . . . . . . . . . . . . . . . . . 5
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5
2. Motivations and Background . . . . . . . . . . . . . . . . . . 5
2.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2. Problem Description . . . . . . . . . . . . . . . . . . . 5
2.3. Requirements . . . . . . . . . . . . . . . . . . . . . . . 6
3. Overview of Operation . . . . . . . . . . . . . . . . . . . . 7
4. Resource Model for Entity-Tags . . . . . . . . . . . . . . . . 10
5. Subscriber Behavior . . . . . . . . . . . . . . . . . . . . . 12
5.1. Detecting Support for Conditional Notification . . . . . . 13
5.2. Generating SUBSCRIBE Requests . . . . . . . . . . . . . . 13
5.3. Receiving NOTIFY Requests . . . . . . . . . . . . . . . . 14
5.4. Polling or Fetching Resource State . . . . . . . . . . . . 15
5.5. Resuming a Subscription . . . . . . . . . . . . . . . . . 17
5.6. Refreshing a Subscription . . . . . . . . . . . . . . . . 18
5.7. Terminating a Subscription . . . . . . . . . . . . . . . . 18
5.8. Handling Transient Errors . . . . . . . . . . . . . . . . 19
6. Notifier Behavior . . . . . . . . . . . . . . . . . . . . . . 20
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