Subject: [Sip] streaming media without sending 18x containing sdp

From: "Brett Tate" <[email-masked]>
Date: Tue, 16 Jan 2007 18:32:10 -0500

Greetings,

I'm trying to understand (or arrive at) the consensus concerning early
media offer/answer within sip when no answer SDP or "preview" answer SDP
is included within the 18x response.  And since there was little
activity on the related sipping and sip-implementors threads, I thought
that I'd try the sip working group and the authors of some of the
relevant RFCs.

When not using early-session (rfc3959), is it appropriate to send early
media to offerer without bothering to send an answer SDP or "preview"
answer SDP within the 18x?  (By "preview", I mean not sent reliably.)

There are of course limitations in not sending the SDP.  Some of the
limitations are reflected in rfc3264, rfc3959, rfc3960, and the
following posting.  The following posting also presents potential
reasons why some vendors might have chosen to act this way.

http://www1.ietf.org/mail-archive/web/sipping/current/msg12640.html

I think that part of my confusion stems from early versions of the early
media drafts indicating things like 18x with sendonly SDP being sent
followed by a 200 with sendrecv SDP.  However after their incorporation
into rfc3261, rfc3262, and rfc3264, I'm uncertain if an SDP needs to be
sent within the 18x.  Based upon rfc3666, the answer does not need to be
sent reliably before acting as answerer.  However if not sent reliably,
does rfc3264 section 6.1 still apply?  And if so, does rfc3264 section
6.1 still apply even when 18x sent without bothering to include the SDP
(the SDP might eventually be sent within an INVITE 200 response)?

Thanks in advance for a response,
Brett

P.S. Sorry about posting my question on yet another email list.

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