Subject: Post-SRV Request-URI (was - [[SIP] A question about Request-URI:])

From: Shail Bhatnagar <[email-masked]>
Date: Thu, 21 Sep 2000 11:16:41 -0400

Forwarding the email using different subject, since this was an
old thread.

Subject: RE: [SIP] A question about Request-URI:
From: "Jo Hornsby" <[email-masked]>
To: "Shail Bhatnagar" <[email-masked]>, "Henning Schulzrinne" <[email-masked]>
Cc: <[email-masked]>
Date: Thu, 21 Sep 2000 09:24:45 +0100

> On a related note, when a proxy does a successful SRV lookup for
> domain.com and gets bigmachine.domain.com,5055 and 
> bigm2.domain.com,6000 and it selects bigmachine.domain.com,5055.
> Should it change the incoming 
> sip:[email-masked] 
> to 
> sip:[email-masked]:5055 ??
> 
> I believe, it should.

Interesting.  I believe it should not. &:)

If you look at the rules of Section 1.4.2, all the magic done
is _based on the Request-URI_; suggesting that the Request-URI
is already well-defined at that point.

Imagine a case where you have a Large Corporation, the ubiquitous
example.com.  Now example.com has two divisions: division1 and
division2.  If there were two distinct Smith's working for
example.com, one in division1 and one in division2, then they
might have the SIP URLs
sip:[email-masked],
sip:[email-masked],
respectively.  Now if there's a large SIP proxy sitting "at the
edge" of example.com, sip.example.com, and this proxy can be
found via SRV, then changing the Request-URI could potentially
result in a fatal loss of information.  Not good.

Of course, as always, proxies are free to do what they want --
it's their birthright; thus there may well be situations where
this is exactly what you want.  In general, however, I would
argue that it is not what you want.

> Also, when forwarding a request using the Route header, should 
> the outgoing Request-URI always be the addr-spec portion of the Route
> header or it can be different due to SRV lookup on the maddr ??

The whole Request-URI in the Route is copied into the Request-URI
proper; maddr, transport (although this should never appear in
a Record-Route/Route), etc., parameters are no-longer illegal here.

HTH,

 - Jo.