Subject: SDP in 1xx responses

From: Eric Tremblay <[email-masked]>
Date: Tue, 27 Apr 1999 15:00:56 -0400

Taken from the notes on Henning's site
(http://www.cs.columbia.edu/~hgs/sip/notes.html)

//-----------
Message Bodies in INVITE and ACK
The caller MAY choose to omit the request body (i.e., not send a session
description) or send a session description that does not list any media
types. This indicates that the caller does not know its desired media
characteristics until the call has been accepted. In this case, the UAS
SHOULD still return a session description in its informational (1xx) or
success (2xx) response, containing those media streams and codecs it
supports. 

If the INVITE request did not contain a complete session description, the
caller MUST include one in the ACK request. A UAC MUSTNOT send an updated
session description in an ACK request if it had already sent a complete
session description in the INVITE request. If the UAC wishes to modify the
session after the call setup has begun, it MUST use another INVITE request
instead. 
//-------------

>From what I read above, a UAS can send back a session description in a 1xx
response, is this correct? If this is the case, section 8.1 in RFC2543
should maybe be updated, as it stated that 1xx responses can include a body
that contains advisory information about the progress of the request.

Thanks,

EricT

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

---

From: "Donovan, Steven R." <[email-masked]>
Date: Wed, 28 Apr 1999 18:29:31 -0000

There are a number of reasons why SDP, or other message bodies, need to be
carried in a 1xx message.  The spec should not limit the message bodies that
can be carried in any of the request or response messages.

Steve

-----Original Message-----
From: Eric Tremblay [mailto:[email-masked]]
Sent: Tuesday, April 27, 1999 2:01 PM
To: [email-masked]
Subject: SDP in 1xx responses

//-----------

Thanks,

EricT