Re: [Sip] Record-Route, Path, Service Route, and Multi-Homed Proxies

["Vijay K. Gurbani" <vkg@lucent.com>]

Hello Dean:

Dean Willis wrote:
> On the weird bits about SIP has always been "how to deal with
> multi-homed proxies". This has begun to raise a mess of problems with
> Path, Service-route, and a few other things I consider important (like
> security).
It also raises (solvable) problems with proxy/registrars being
authoritative entities for multiple domains, each represented by a
different interface.  We've run into some of these while running
on multi-homed machines.

In any case, regarding your specific proposal, it sounds eminently
reasonable.  For much the same reasons as you mention (not so much as
breaking e2e security model as for the intensive task of modifying
R-R responses going upstream; more so if the request has legitimately
spiralled and thus the need to find the appropriately inserted R-R), I
have not been a big fan of R-R response modifications (rfc3261 does
have an example, I believe, in Chapter 17).  Maitaining two Routes
in the Route set leads to simpler processing (optimizing proxies can
prevent double processing, as you point out).

> Path Forward:
>
> If nobody convinces me this is just a freaking bad idea, I propose to
> document the record-route behavior in a new draft, and edit the
> Service-Route draft to reference the behavior and describe how to
> generate service-routes from record-routes. I believe all the
> implications for Path (currently in rfc-ed queue) can be handled
> entirely within the Service Route draft.
Must we come up with a new I-D for this?  It is not new SIP behavior
as much as heuristics/clarification/discussion on how a proxy/registrar
behaves under a multi-homed machine.  I mean, if rfc3261 does not
address multi-homing, can we add a section in Chapter 17?  There are a
list of open issues associated with rfc3261 anyway.  My personal
preference is to add it in rfc3261-bis since the 
heuristics/clarifications/discussions do really belong there.

Regards,

- vijay
--
Vijay K. Gurbani  vkg@{lucent.com,research.bell-labs.com,acm.org}
Wireless Networks Group/Internet Software and Services
Lucent Technologies/Bell Labs Innovations, 2000 Lucent Lane, Rm 6G-440
Naperville, Illinois 60566     Voice: +1 630 224 0216

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