Subject: SIP Redirect Server

From: Eric Tremblay <[email-masked]>
Date: Thu, 18 Jun 1998 19:28:54 -0400

Can a redirect server redirect other requests than INVITE?  Or must a
UAC be prepared to handle a 301/302 response when sending BYEs?  I don't
think it should, but I want to make sure, because this might cause a
small problem.

Thank you,
EricT

Eric Tremblay       | Mediatrix Telecom
Ingénieur Stagiaire | -----------------
email: [email-masked]
Tel: +1(819)829-8749 ext. 238
Web: www.mediatrix.com

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From: Mark Handley <[email-masked]>
Date: Thu, 18 Jun 1998 20:03:10 -0400

>Can a redirect server redirect other requests than INVITE?  

Yes, it can.  Especially with OPTIONS or REGISTER methods.

>Or must a

I don't think it makes sense to redirect a BYE, ACK or CANCEL.  If the
server doesn't have enough information to handle one of these
requests, I would normally expect it to return 481 (Invalid Call-ID).

Perhaps we should state this explicitly as a general rule for 3xx
responses?

Mark

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From: Henning Schulzrinne <[email-masked]>
Date: Thu, 18 Jun 1998 21:14:24 -0400

> Can a redirect server redirect other requests than INVITE? 

Yes, I don't see why not. With the exception of ACK (and CANCEL, see
below), obviously, as this would be directed at ack'ing a previous
exchange, not as a new request.

> think it should, but I want to make sure, because this might cause a

What small problem did you have in mind? I'm inclined (in the interest
of generality) to allow redirection on any non-ACK request, as it makes
mobility a lot easier.

That said, it is not quite clear to me if CANCEL redirection makes a lot
of sense, however. If I send a CANCEL to a redirect server I would
presumably want to tell it to stop rummaging through its databases.

Generally, BYE redirect should not happen, as the INVITE response will
indicate a direct path to the invited entity. But if I send the BYE to
the same redirect server I sent my INVITE to, what else is the poor
redirect server to do?

I'll add some wording to the spec, unless there are better suggestions
of redirect behavior.