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[AVT] Doubts in draft-ietf-avt-rfc2429-bis-09.txt

"Huve, Frederic" <frederic.huve@hp.com> Tue, 28 November 2006 16:00 UTC

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From: "Huve, Frederic" <frederic.huve@hp.com>
To: roni.even@polycom.co.il
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Subject: [AVT] Doubts in draft-ietf-avt-rfc2429-bis-09.txt
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Roni,

We're investigating to move from RFC 2429 support to rfc2419-bis-09
support and it remains one question around Offer/Answer. (I've browsed
the mail archive and partially found part of the response
http://www1.ietf.org/mail-archive/web/avt/current/msg06890.html :)

In the following use case, what is the valid SDP Offer/Answer scenario ?

If an offerer sends a SDP offer (meaning he wants to receive QCIF with
MPI = 2):
 
m=video 8000 RTP/AVP 96
a=rtpmap:96 H263-1998/90000
a=fmtp:96 QCIF=2
a=sendrecv
 
The answerer sends the following SDP answer (means that he can receive
up to CIF with MPI = 1):

m=video 8002 RTP/AVP 96
a=rtpmap:96 H263-1998/90000
a=fmtp:96 CIF=1
a=sendrecv

IMHO this scenario is not valid because of the RFC-2429bis statement: "
A system that declares support of a specific MPI for one of the
resolutions SHALL also implicitly support a lower resolution with the
same MPI."

In order to be compliant the answerer should instead responds with the
following SDP answer: 

m=video 8002 RTP/AVP 96
a=rtpmap:96 H263-1998/90000
a=fmtp:96 CIF=2
a=sendrecv


Warm thanks for your time !
Regards,
Frederic

frederic.huve@hp.com

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