Subject: [MMUSIC] comment on draft-ietf-mmusic-sdpng-trans-00.txt

From: Jonathan Rosenberg <[email-masked]>
Date: Fri, 08 Mar 2002 01:15:00 -0500

I had a comment on the SIP migration strategy discussed in this draft.

One of the mechanisms that is proposed is the usage of
multipart/alternative. Unfortunately, sip-bis doesn't really talk about
using multipart/alternative for session descriptions. I suspect most
implementations would reject this, even if they support other multipart
types.

An alternative is the use the UPDATE method. Indeed, dealing with SDPng
transition was one of the first cases where we saw the "heterogeneous
error response forking problem" arise, for which UPDATE was proposed as
a fix. The basic idea is, you send the INVITE with SDPng. The UAS
doesn't support it. Instead of rejecting it, it sends a 155 response
back, indicating that SDPng is not supported. The UAC sends an UPDATE
with SDP instead, and then the session proceeds. The benefit of doing
this, instead of having the UAS send a 415, is that a whole bunch of
forking related services and applications get fouled up with 415, and
they don't get fouled up with a 155.

It might be worth mentioning of this in the sdpng-trans draft.

Thanks,
Jonathan R.
-- 
Jonathan D. Rosenberg, Ph.D.            72 Eagle Rock Avenue
Chief Scientist                         First Floor
dynamicsoft                             East Hanover, NJ 07936
[email-masked]                 FAX: (973) 952-5050
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From: Colin Perkins <[email-masked]>
Date: Thu, 14 Mar 2002 12:10:26 -0500

>implementations would reject this, even if they support other multipart

Doesn't entirely surprise me, and I suspect we'll see similar issues with
the other uses of SDP.

>It might be worth mentioning of this in the sdpng-trans draft.

Agreed.

Colin