Technical Summary
This document updates the framework for preconditions in SIP. It
clarifies RFC 3312; it does not obsolete RFC 3312, but just explains
it better and adds some rules that update it. It provides guidelines for
authors who plan to write new precondition types, beyond the qos
precondition.
In addition, this document describes and solves some issues concerning
the interaction between session mobility and preconditions.
Working Group Summary
The working group supported advancement of this document.
Protocol Quality
The concerns about session mobility were identified in implementation
experiences. The document was reviewed for the IESG by Allison Mankin
and by Spencer Dawkins of the General Area Review Team.
RFC Editor Notes
Abstract:
OLD:
This document updates the framework for preconditions in SIP.
NEW:
This document updates RFC 3312, which defines the framework for
preconditions in SIP.
Add the following paragraph to the end of the Introduction:
Specifically, we now allow answers to downgrade current status values
(this was disallowed by RFC 3312). We consider moving an existing stream
to a new location as equivalent to establishing a new stream. Therefore,
answerers moving streams to new locations set all the current status
values in their answers to "No" and start a new precondition negotiation
from scratch.
Section 4.1
OLD:
Table 3 of RFC 3312 [3] needs to be updated to allow answers to
downgrade current status values.
NEW:
Table 3 of RFC 3312 needs to be updated to allow answerers to
downgrade current status values.
Section 6
IANA Considerations
OLD:
This document has no IANA considerations.
NEW:
The IANA registration requirements for the preconditions framework are
defined in RFC 3312. Any new preconditions are governed by the IANA
Considerations there.
Throughout the document:
After the first reference to [3], omit the [3].