Minutes, SIP WG, IETF 58
Official Scribe, Ben Campbell

Supplementary Scribe, Vijay Gurbani

Minutes Edited by Dean Willis





Topic: Call to Order and Agenda Bash

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No issues raised.



Topic: Status, Chairs

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Slides presented.



New milestones proposed. No schedule objections raised, but it was
proposed that the app-interaction framework be published as a proposed
standard instead of BCP. Concerns about MIB status raised. Noted that
SIP should certainly plan to operate at least through the current
work-elevation plan from SIPPING, which extends through December 2004. 

Topic: Congestion Safety,  Dean Willis

---------------------------------------

Reading list:

   draft-ietf-sip-congest-safe-02

   

There appears to be little interest in implementing this draft. 
Some suggestions for simplifying it were made. It was also suggested
that we need to change RFC 3263to prefer TCP over UDP, explain
congestion issues and avoidance in a BCP, and complete the connection
reuse work in order to encourage TCP deployment. Many endpoints now
implement only UDP. We also need to differentiate fragmentation and
congestion. It was noted that this problem does not just apply to
MESSAGE, but can be frequently expected with NOTIFY, and with INVITES
using S/MIME protection. DCCP is only a partial solution. Several
people volunteered to work on this proposed BCP.



It was also suggested that the current draft could be simplified to
eliminate new response codes 515 and 516, providing a minimal "NO UDP"
assurance. 





Topic: RFC 3312 Updates, Gonzalo Camarillo

Reading list:

    draft-camarillo-sip-rfc3312-update-00.txt



Slides presented. 



Suggested that we adopt as WG item. No objections were raised. 



Conclusion: adopt draft as wg item, negotiate milestone.








Topic: Publish, Aki Niemi

Reading List:

    draft-ietf-sip-publish-01



Slides presented.



Issue: Should etags be updated on every publish? Consensus: Usage
should be made consistent with HTTP. If it cannot be, we should call
these something else.



Issue: Publication rate. Proposed that rate from event package be used.
Noted that this is probably an irrelevant and meaningless number, as
there may be multiple publishers with no knowledge of each other. Much
debate ensued, with no resolution  Further discussion deferred to
the mailing list.







Topic:  Request History, Mary Barnes

Reading List:

    draft-ietf-sip-history-info-01

    draft-jennings-sip-voicemail-uri-00.txt

    RFC 3087



Slides presented.



Issue: r-uri captured anytime request is forwarded. Proposal: Only add
reason for history entries added due to retargeting.




Issue: Privacy. Proposal: information not included when there are
privacy
considerations. (when uas sets session or header level privacy)
.



Next steps: complete flow detail. Do we want to fold reqs into doc as
front matter? Request more mailing list feedback. Dependency on mid-end
security draft.


Presentation of applicability to voicemail.




Issue: Optionality. Suggested that we apply stronger language to
suggest applications gracefully
degrade in absence of history.




Issue: Implementability: Concerns raised by Robert Sparks, who will
detail on mailing list.



Issue: Security. Note that this in-general seems to depend on the
middle-to-end and end-to-middle security work.



Conclusion: Work should continue, but more thinking about
optionality is needed. RJS and Mary to talk offline.








1400 Non-Invite Transactions,   Robert Sparks

Reading list:

    draft-sparks-sip-noninvite-01.txt



Slides presented.



Noted that this problem is not related to the transport protocol, but
is specific to the SIP-layer transaction reliability mechanism for all
transactions other than INVITE.



Several alternatives were presented: 



A) a series of tweaks

B) Eliminate Timer F, allowing non-invite transactions to pend.

C) USe path-timing estimation techniques to improve UAs knowledge of
timing.

D) Revise 3263 caching language to reduce severity of impact.

E) Ignore the problem



Suggested that SIP be revised to use 3-way handshake like INVITE on all
transactions. This might be made backward-compatible through use of an
option tag.



Polls indicated  no consensus on any action, and that the working
group didn't understand the nature of problem or disagreed as to its
severity. Despite the objections of Morton Thiokol engineers, the
shuttle was launched in cold-weather conditions under which it had
never been tested, and the O-rings in the boosters failed.



Conclusion: None. Further discussion deferred to the mailing list.





Topic: GRUU, Jonathan Rosenberg

Reading list:

    draft-rosenberg-sip-gruu-00.txt

    draft-rosenberg-sipping-gruu-reqs-01.txt



Slides presented.



Issue: GRUU generation for stateless proxy behavior. Consensus that we
need a sample algorithm for understanding.



Issues: Liftime
of a GRUU. Can a gruu change during a registration? Conclusion: No,
gruu is good for lifetime of registrations, refreshes get same gruu.


Do we need a guarantee of difference between registrations? Probably
no,
discuss on list.




Issue: Dialog reuse—no longer a need with gruu. Should gruu spec
deprecate
dialog resuse if both peers support gruu? (Impacts refer, other
subscribe usage).


Conclusion: Do not address in gruu spec, address in other drafts, put
pressure on future work to avoid dialog resuse.




Issue: Does Gruu interferes with e2e signaling. UA can try to generate
a local
gruu, could use ice-like mechaninsm to decide if it is reachable.
Propose to add to draft, but never try to put local address in contact
header without using the mechanism. 
Chair suggestion: Put statement about not using local gruu in gruu
draft, put “iceing” in separate draft. Author agreed.




Issue:  MUST NOT use locally generated gruu is too strong.
Clarified that definition of local gruu is one with a different domain
part than AoR,
MUST does not apply to the examples given.






Topic: Join,  Rohan Mahy

Reading List:

    draft-ietf-sip-join-02.txt



Slides presented.



Noted that no comments in wglc. Room shows interest, but no one has
implemented.


We want more list discussion before sending to IESG.








Topic: REFER Semantics, Rohan Mahy   

Reading List:

    draft-olson-sipping-refer-extensions

    draft-mahy-sip-remote-cc



Slides presented. 



Basic premise is that the semantics of  the various uses of REFER
are under-specified. Much discussion ensued.





Issue: Is this equivalent to specifying fixed services? If we have
to specify all the services/features, then the refer approach has
failed.




Issue: How do you put refer requests in a context? Dialog reuse?
Separate
GRUUs? Explicit refer-to header parameters? 
Noted that it may require per-scheme semantics in addition to context.




Issue: Need more than context—how do you know what an endpoint will do
with a particular URI scheme?




Issue: Not useful for authorization, because referee cannot decide if
issuing the request could be bad. Another motivation that is relevant
is to determine how to render the UI for the action.




Sugested: this does not mean fixing refer, it means adding something
new to
it.




Discussion on proceeding: How do we proceed? Refer for other than
transfer unlikely to work on
today’s UAs. Rohan suggests defining semantics for baskets of
functionality. Use option tags to make sure they are supported. Propose
explicit dialog parameters for refer-to. Provide guidance for remote
call control vs. remote UI invocation.




No conclusion, further discussion deferred to list. Interested parties
are to contact Rohan and work on it.





Final To-Do:

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App Interaction Framework -- change from BCP to PS.

Add milestone for RFC 3312 update as PS.

Discuss publication rate on mailing list.