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Re: [pntaw] Real-time media over TCP

Harald Alvestrand <harald@alvestrand.no> Tue, 08 October 2013 04:09 UTC

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Date: Tue, 08 Oct 2013 06:09:35 +0200
From: Harald Alvestrand <harald@alvestrand.no>
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To: Michael Tuexen <Michael.Tuexen@lurchi.franken.de>, Dan Wing <dwing@cisco.com>
References: <CAGTXFp92jSzQz05uHngzscz88n=fT_JPbEvQRxgeUUqPVRQUyQ@mail.gmail.com> <52244DD7.1020900@alvestrand.no> <BLU405-EAS183E36A927CA42270B6936D93300@phx.gbl> <522590EE.7070508@alvestrand.no> <C632A223-A55A-47F4-B083-9BDC447DA959@cisco.com> <52262657.3080208@alvestrand.no> <A2C315DB-1882-4BD1-A8C0-E8AF7DEA48F4@cisco.com> <00ca01cec387$f881cae0$e98560a0$@co.in> <BLU406-EAS274696C3D9DFE505F96B8E393130@phx.gbl> <2924C1EA-613D-4B05-BD24-4CFD1411386E@cisco.com> <28C05866-180F-41B2-8466-502F57FF1DF1@lurchi.franken.de>
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Cc: Bernard Aboba <bernard_aboba@hotmail.com>, "pntaw@ietf.org" <pntaw@ietf.org>, Parthasarathi R <partha@parthasarathi.co.in>
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 <dwing@cisco.com> wrote:
>
>>
>> On Oct 7, 2013, at 11:32 AM, Bernard Aboba
<bernard_aboba@hotmail.com> 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
privileges...
> 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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