Re: [AVT] RTP w/ TCP, RTP w/o RTCP ...

inline.

John Lazzaro wrote:
> Hi everyone,
> 
> 	Work is proceeding on the MWPP "implementation guidelines" I-D
> revision. The main body of the text is now finished (implementation
> guidance for a two-party interactive session over unreliable unicast
> UDP, with RTCP), and I'm starting to work on the Appendices which
> cover other types of sessions. A few issues have come up:
> 
> 
>   [1] One Appendix focuses on how to send RTP w/o RTCP. Looking over the
>   mmusic I-Ds and RFCs, I couldn't find a way to express "I am sending
>   RTP w/o RTCP" in an SDP m= line. I was expecting the "RTCP attribute
>   in SDP" I-D (draft-ietf-mmusic-sdp4nat-03.txt) to have syntax for
>   "none", but it doesn't seem to (maybe I missed it).

Try:
http://www.ietf.org/internet-drafts/draft-ietf-avt-rtcp-bw-05.txt

>   [2] Another Appendix focuses on how to send RTP over TCP. For the
>   special case of using RTSP and interleaved mode, sending RTP over TCP
>   is fully specified. I could just write this Appendix around RTSP.
> 
>   However, some MWPP users will be doing interactive work using TCP, 
>   and so RTSP isn't the right session management tool for them, SIP is.
>   The draft-ietf-mmusic-sdp-comedia-04.txt document describes how to
>   create the SDP lines for specifying TCP, so I was going to base the
>   interactive story around that syntax.
> 
>   The open issue is the encapsulation of RTP and RTCP in the byte
>   stream. Section 7 of draft-ietf-avt-profile-new-12 doesn't specify a
>   standardized method for encapsulation, but rather says it is
>   "application dependent", and cites RTSP as an example.
> 
>   This would seem to indicate that there is a SIP-oriented I-D
>   somewhere, that standardizes a byte stream encapsulation for use with
>   draft-ietf-mmusic-sdp-comedia-04.txt. Does such a document exist?

No. Comedia was meant for non-RTP applications primarily (at least where 
TCP is concerned). It used to be that you could use a certain character 
in the TCP stream (* maybe?) to frame RTP packets, but this was removed 
because no one implemented it.

-Jonathan R.

-- 
Jonathan D. Rosenberg, Ph.D.                72 Eagle Rock Ave.
Chief Scientist                             First Floor
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