Re: [pntaw] Real-time media over TCP

Harald Alvestrand <harald@alvestrand.no> Tue, 08 October 2013 04:32 UTC

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Date: Tue, 08 Oct 2013 06:32:04 +0200
From: Harald Alvestrand <harald@alvestrand.no>
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Subject: Re: [pntaw] Real-time media over TCP
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On 10/07/2013 08:06 PM, Parthasarathi R wrote:
> Hi all,
>
> RTP over TCP is unavoidable in case of RTCWeb media traffic has to traverse
> through UDP blocking firewalls. TCP candidates with ICE (RFC 6544) may fail
> due to the current OS implementation wherein TCP simultaneous Open will not
> work. 
>
> I have concern w.r.t TURN server as it introduces one extra network element
> for RTCWeb session establishment. The current argument favoring for TURN
> server is that RTP over TCP is required only till TURN server whereas the
> media traffic between TURN server and the destination is UDP.

Don't forget the (likely) case where the destination is also reached
through a TURN server, so that the path is

user 1->TCP->TURN server 1->UDP->TURN server 2->TCP->user 2

For extra irony, the two clients may be using the same TURN service, so
that the UDP hop is an intra-datacenter or even intra-machine hop :-)