Explicit Subscriptions for the REFER Method
RFC 7614
Internet Engineering Task Force (IETF) R. Sparks
Request for Comments: 7614 Oracle
Category: Standards Track August 2015
ISSN: 2070-1721
Explicit Subscriptions for the REFER Method
Abstract
The Session Initiation Protocol (SIP) REFER request, as defined by
RFC 3515, triggers an implicit SIP-Specific Event Notification
framework subscription. Conflating the start of the subscription
with handling the REFER request makes negotiating SUBSCRIBE
extensions impossible and complicates avoiding SIP dialog sharing.
This document defines extensions to REFER that remove the implicit
subscription and, if desired, replace it with an explicit one.
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/rfc7614.
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Sparks Standards Track [Page 1]
RFC 7614 REFER Explicit Subscriptions August 2015
Table of Contents
1. Introduction ....................................................3
2. Conventions .....................................................3
3. Overview ........................................................4
3.1. Explicit Subscriptions .....................................4
3.2. No Subscriptions ...........................................5
4. The Explicit Subscription Extension .............................5
4.1. Sending a REFER ............................................5
4.2. Processing a REFER Response ................................5
4.3. Processing a Received REFER ................................6
4.4. Subscribing to the 'refer' Event ...........................7
4.5. Processing a Received SUBSCRIBE ............................7
4.6. Sending a NOTIFY ...........................................7
4.7. Managing 'refer' Event State ...............................8
4.8. The Refer-Events-At Header Field ...........................8
5. The No Subscription Extension ...................................9
5.1. Sending a REFER ............................................9
5.2. Processing a REFER Response ................................9
5.3. Processing a Received REFER ................................9
6. The 'explicitsub' and 'nosub' Option Tags ......................10
7. Updates to RFC 3515 ............................................10
8. Security Considerations ........................................10
9. IANA Considerations ............................................12
9.1. Register the 'explicitsub' Option Tag .....................12
9.2. Register the 'nosub' Option Tag ...........................12
9.3. Register the Refer-Events-At Header Field .................12
10. References ....................................................13
10.1. Normative References .....................................13
10.2. Informative References ...................................13
Author's Address ..................................................14
Sparks Standards Track [Page 2]
RFC 7614 REFER Explicit Subscriptions August 2015
1. Introduction
REFER, as defined by [RFC3515], triggers an implicit SIP-Specific
Event Framework subscription. Sending a REFER within a dialog
established by an INVITE results in dialog reuse and the associated
problems described in [RFC5057]. The SIP-Specific Event Notification
framework definition [RFC6665] disallows such dialog reuse. Call
transfer, as defined in [RFC5589], thus requires sending a REFER
request on a new dialog, associating it with an existing dialog using
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