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

From: John Lazzaro <[email-masked]>
Date: Sun, 1 Dec 2002 14:08:27 -0800

> Colin Perkins <[email-masked]> writes:
>
> If it's useful, we might reconsider making a generic TCP framing?

I'll write it into the document in a modular way, so if there is
interest it can be broken out into a separate I-D ... 

The MWPP need for a TCP option is for "archival" applications, where
a musician's MIDI stream is being recorded for later use. Probably in
some sort of recording studio application, running over a switched LAN
that "almost" never drops packets.

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John Lazzaro -- Research Specialist -- CS Division -- EECS -- UC Berkeley
lazzaro [at] cs [dot] berkeley [dot] edu     www.cs.berkeley.edu/~lazzaro
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_______________________________________________
Audio/Video Transport Working Group
[email-masked]
https://www1.ietf.org/mailman/listinfo/avt

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From: Chuck Harrison <[email-masked]>
Date: Sun, 01 Dec 2002 14:35:21 -0800

John, all,

John Lazzaro wrote:
[...]
> that "almost" never drops packets.

I have been thinking about how to combine archiving with a
latency-constrained realtime stream and came up with an
alternative approach. Let the realtime sink device and the
archive device both be subscribed to the sending session
using conventional RTP/UDP. The archive device uses the
RTP retransmission protocol to request fixes for any errors
it sees in the stream.

Make any sense?

Cheers,
  Chuck

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From: Colin Perkins <[email-masked]>
Date: Sun, 01 Dec 2002 19:56:42 -0500

>RTP retransmission protocol to request fixes for any errors

Yes, provided the retransmission requests are timed to avoid congesting 
the link.

Colin

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From: Jonathan Lennox <[email-masked]>
Date: Mon, 2 Dec 2002 10:28:23 -0500

> interest it can be broken out into a separate I-D ... 

The generic framing in the old RTP spec was just "16-bit packet length in
network byte order, followed by packet."

I've written a program that uses this format to tunnel UDP through TCP
sessions, useful for getting plain-mbone-tools RTP sessions past firewalls.
See <http://www.cs.columbia.edu/~lennox/udptunnel/>.

-- 
Jonathan Lennox
[email-masked]

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From: Stephen Casner <[email-masked]>
Date: Tue, 3 Dec 2002 23:14:22 -0800 (PST)

> RTP retransmission protocol to request fixes for any errors

We've talked about this a number of times over the past few years.
The split is not binary, either: real-time receivers can listen to the
retransmissions as well and have a knob to trade off latency vs. loss
rate.

                                                        -- Steve