An Extension to Session Initiation Protocol (SIP) Events for Conditional Event Notification
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From: The IESG <email@example.com> To: IETF-Announce <firstname.lastname@example.org> Cc: Internet Architecture Board <email@example.com>, RFC Editor <firstname.lastname@example.org>, sipcore mailing list <email@example.com>, sipcore chair <firstname.lastname@example.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.