Re: [pntaw] Real-time media over TCP

On Oct 14, 2013, at 11:02 PM, Tirumaleswar Reddy (tireddy) <tireddy@cisco.com> wrote:

>> -----Original Message-----
>> From: pntaw-bounces@ietf.org [mailto:pntaw-bounces@ietf.org] On Behalf Of Dan
>> Wing (dwing)
>> Sent: Tuesday, October 15, 2013 5:31 AM
>> To: Markus.Isomaki@nokia.com
>> Cc: pntaw@ietf.org; partha@parthasarathi.co.in
>> Subject: Re: [pntaw] Real-time media over TCP
>> 
>> 
>> 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.
> 
> But firewall TCP inspection causes the inbound SYN from the same host/port to be dropped (Firewalls typically do not permit TCP simultaneous-open). Even with NAT as per the survey results in ICE TCP (http://tools.ietf.org/html/rfc6544#appendix-A) TCP simultaneous-open worked only in roughly 45% of the cases.

If avoiding TURN improves the user experience, and IT policy says TCP is allowed, I expect firewall vendors would make sure TCP simultaneous open works.

-d

> 
> -Tiru.
> 
>> 
>> -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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