Re: [pntaw] Real-time media over TCP

Dan Wing <dwing@cisco.com> Tue, 15 October 2013 00:01 UTC

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From: Dan Wing <dwing@cisco.com>
In-Reply-To: <E44893DD4E290745BB608EB23FDDB7620A0E7172@008-AM1MPN1-043.mgdnok.nokia.com>
Date: Mon, 14 Oct 2013 17:01:26 -0700
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To: Markus.Isomaki@nokia.com
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Cc: pntaw@ietf.org, partha@parthasarathi.co.in
Subject: Re: [pntaw] Real-time media over TCP
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On Oct 14, 2013, at 12:06 PM, Markus.Isomaki@nokia.com wrote:

> Hi,
> 
> In practice I doubt you find many situations where UDP is completely blocked but incoming TCP connections from anywhere are allowed.

Agreed.  

But if both ends are trying to communicate with each other, their communications will appear as a TCP simultaneous-open.  That could (in fact, "should") work across a firewall because the firewall will see an outbound SYN to a host/port after which it will see an inbound SYN from that same host/port.

-d


> I'm not sure the use cases and requirements document really claims that to be the case, but I agree it is somewhat ambiguous. That means that while direct TCP connection would be better than TCP based relay, its success rate would be very small. I suppose we agree that UDP based relay would still be better than direct TCP for real-time media.
> 
> Markus
> 
>> -----Original Message-----
>> From: pntaw-bounces@ietf.org [mailto:pntaw-bounces@ietf.org] On Behalf
>> Of ext Parthasarathi R
>> Sent: 14 October, 2013 21:55
>> To: pntaw@ietf.org
>> Subject: Re: [pntaw] Real-time media over TCP
>> 
>> Hi all,
>> 
>> My point is that the direct media connection has to be given priority over
>> TURN based mechanism. In case of ICE-TCP, there is a possibility for the
>> direction connection between two browsers involved in the WebRTC session
>> and should be given priority over TURN based mechanism. So, 6) TCP based
>> candidates (ICE-TCP) - MUST
>> 
>> There is an assumption in the discussion that the incoming TCP traffic is not
>> allowed through firewall. In case it is the problem to be solved, RTCWeb
>> usecase and requirement has to be updated. I noticed in
>> draft-ietf-rtcweb-use-cases-and-requirements-12 (published today) that
>> there is no such requirement. I'll write the mail in RTCWeb WG to get the
>> clarity on the requirement in case the firewall forbidding incoming TCP traffic
>> is a matter of missing text in the requirement.
>> 
>> Thanks
>> Partha
>> 
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