The Session Initiation Protocol (SIP) REFER request, as defined by
RFC3515, 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 to prevent the implicit
subscription and, if desired, replace it with an explicit one.
Working Group Summary
There was some controversy and difficulty in reaching agreement on this draft.
Before work on this draft and the companion draft (draft-ietf-sipcore-refer-
clarifications) commenced, some (notably 3GPP) made attempts to use existing
mechanisms (RFC4488) to avoid the need for GRUUs. That mechanism as insufficient
on its own, and so was enhanced with particular conventions. There was a desire
to maintain compatibility with that work. This led to careful word smithing.
That has been discussed at length within the WG. The results are now acceptable
to all parties.
The shepherd is not aware of any implementations yet.
It is the shepherd's understanding that 3GPP release 12 has a reference,
indicating that implementations can be expected.
This document has been thoroughly reviewed and discussed. Everyone
that had something to say has aired it.
The document shepherd is Paul Kyzivat.
The area director is Ben Campbell.