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

From: John Lazzaro <[email-masked]>
Date: Fri, 29 Nov 2002 18:19:06 -0800

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).

  Is there way to express this in a standardized way? Or is the default
  to use the normal m= line but not to send RTCP, with the expectation
  that receivers act gracefully if no packets arrive on the RTCP port?

  [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?

	Thanks in advance, 

-------------------------------------------------------------------------
John Lazzaro -- Research Specialist -- CS Division -- EECS -- UC Berkeley
lazzaro [at] cs [dot] berkeley [dot] edu     www.cs.berkeley.edu/~lazzaro
-------------------------------------------------------------------------

_______________________________________________
Audio/Video Transport Working Group
[email-masked]
https://www1.ietf.org/mailman/listinfo/avt

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From: Jonathan Rosenberg <[email-masked]>
Date: Sat, 30 Nov 2002 23:19:14 -0500

inline.

>   "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

>   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.

-- 
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