Re: [pntaw] Real-time media over TCP

Harald Alvestrand <> Tue, 08 October 2013 04:09 UTC

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Date: Tue, 08 Oct 2013 06:09:35 +0200
From: Harald Alvestrand <>
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To: Michael Tuexen <>, Dan Wing <>
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Cc: Bernard Aboba <>, "" <>, Parthasarathi R <>
Subject: Re: [pntaw] Real-time media over TCP
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On 10/07/2013 10:14 PM, Michael Tuexen wrote:
> On Oct 7, 2013, at 10:08 PM, Dan Wing <> wrote:
>> On Oct 7, 2013, at 11:32 AM, Bernard Aboba
<> wrote:
>>> As you point out, in most cases ICE-TCP will not avoid use of TURN,
so we are only talking about a modest efficiency gain for ICE-TCP and
RTP over TCP, but a substantial increase in complexity.
>>> Running SCTP over TCP is undesirable because the congestion control
in SCTP and TCP will interact poorly with each other. 
>> And, even if a full SCTP stack is run over a full TCP stack, that
will work but I agree won't work well.  But working is better than not
working in situations where UDP is blocked.
>> To work well, we might look at SCTP Minion
(draft-iyengar-minion-concept, which disables TCP's congestion control
in lieu of SCTP's congestion control) is one answer to those conflicting
congestion controls.
> This would either require changing the TCP stack in the kernel or using a
> userland TCP stack without CC, which would require using a raw socket for
> sending, for receiving some other strategy, both would require root
> Or am I missing something?

If I remember the minion overview correctly, it will in fact work on an
unmodified TCP stack, but if there are ioctls available to get frames
out of order, it can work a good deal better.

But you should get Iengar himself to talk about it if it's of interest.

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