Subject: Re: [SIP] Contact in OPTIONS

From: [email-masked] (Vijay K Gurbani)
Date: Mon, 29 May 2000 23:32:32 -0500

Henning Schulzrinne wrote:
> to have proxies insert Record-Route in every request. That way, the
> rebooted component will still get the right information. This would seem
> to be backward compatible. In this model, once a proxy adds itself to
> the route, it cannot delete itself, i.e., *not* including does not imply
> dropping out. Also, changing RR entries (for example, changing the maddr
> part) could not be guaranteed to be respected by the other side.
> 
> Would this work?

Jonathan Rosenberg wrote:
> This definitely works. Basically, what it means is that so long as a UA
> has state for the call, it keeps the original route and does not try to
> update. If, however, it crashes and restarts, it uses whatever it gets
> in the request. This would allow it to do a partial reconstruction of
> the route - "better than nothing" kind of thing, with increasing
> performance as this feature is spread.
> 
> In addition to this, we can define an explicit "remove me" record-route
> entry. Something like:
> 
> Remove-Route: <sip:user@host;maddr=1.2.3.4>;remove=true
> 
> Proxies would add this when they want out. A UA not understanding this
> will ignore out continue to use the old route, but a new UA would know
> that this means to remove it from the Route in the next request. I think
> this is also backwards compatible. 
> 
> Both of these mechanisms combined (remove-route and adding record-route
> for mid-call messages) has the desired result of being backwards
> compatible, providing for restarts after crashes, and allowing proxies
> to remove themselves during a call.

Jonathan:

Are you proposing a new header called "Remove-Route" or a new parameter
("remove=true") to the Record-Route header?  If Remove-Route will be
present in the general headers, why the "remove=true" parameter?

But yes, this should work, although deployed proxies may still think
that if they have included "Record-Route" in a previous request, that's
all they have to do.

Thanks,

- vijay
--
Vijay K. Gurbani  vkg@{lucent.com,research.bell-labs.com,acm.org}
IN Architecture and Internet Software Group 
Lucent Technologies/Bell Labs Innovations 263 Shuman Blvd., Rm 1A-418
Naperville, Illinois 60566     Voice: +1 630 224 0216   Fax: +1 630 713 0184

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From: Jonathan Rosenberg <[email-masked]>
Date: Tue, 30 May 2000 01:03:49 -0400

> present in the general headers, why the "remove=true" parameter?

Email edit error. I initially wrote it as part of Record-Route, and then
changed my mind, but forgot to remote ;remove=true. So, its a new header
(I'm not proposing it yet, though.... I'm still looking for some cases
where its needed).

> that if they have included "Record-Route" in a previous request, that's

Right, and it is. They will receive all requests for the call. Only if
the client crashes and reboots, then it won't get any subsequent
signaling if recovery takes place. Only new proxies would. Also, only
new proxies can remove themselves. But thats all fine - new features in
the new proxies, but still backwards compatible.

-Jonathan R.
-- 
Jonathan D. Rosenberg                       72 Eagle Rock Ave.
Chief Scientist                             First Floor
dynamicsoft                                 East Hanover, NJ 07936
[email-masked]                     FAX:   (732) 741-4778
http://www.cs.columbia.edu/~jdrosen         PHONE: (732) 741-7244
http://www.dynamicsoft.com

---

From: Jonathan Rosenberg <[email-masked]>
Date: Tue, 30 May 2000 01:03:49 -0400

-Jonathan R.