Re: [pntaw] Real-time media over TCP

["Parthasarathi R" <[e-mail]>]

Hi Harald & all,

I agree that ICE-TCP qualifies for "MAY" requirement in case both browsers
are behind firewall. ICE-TCP is good for usecase wherein only one of the
browsers is behind firewall. Existing WebRTC usecase namely FedEx call is
good example for only one browser behind firewall wherein IVR is not going
to be behind UDP blocking firewall. In those usecases, ICE-TCP candidates
has merits over TURN relay candidates. IMO, ICE-TCP MUST be considered.

The current WebRTC FW usecase is (accidentially) inline with one of the
browser behind firewall scenario as mentioned in sec 3.3.2.1 of
draft-ietf-rtcweb-use-cases-and-requirements-12:

"The difference is that one of the users is behind a NAT that blocks UDP
traffic."

Thanks
Partha

> -----Original Message-----
> From: [e-mail] [mailto:[e-mail]] On Behalf
> Of Harald Alvestrand
> Sent: Wednesday, October 16, 2013 5:33 PM
> To: [e-mail]
> Subject: Re: [pntaw] Real-time media over TCP
> 
> On 10/15/2013 06:15 PM, Dan Wing wrote:
> > On Oct 14, 2013, at 11:02 PM, Tirumaleswar Reddy (tireddy)
> <[e-mail]> wrote:
> >
> >>> -----Original Message-----
> >>> From: [e-mail] [mailto:[e-mail]] On
> Behalf Of Dan
> >>> Wing (dwing)
> >>> Sent: Tuesday, October 15, 2013 5:31 AM
> >>> To: [e-mail]
> >>> Cc: [e-mail]; [e-mail]
> >>> Subject: Re: [pntaw] Real-time media over TCP
> >>>
> >>>
> >>> On Oct 14, 2013, at 12:06 PM, [e-mail] 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.
> >
> >
> If something improves the user experience if it is possible to do it,
> but the basic functionality works without it, and it's unclear whether
> the special circumstances under which it's going to improve the user
> experience in fact exist in the field, I think that's perfect for a MAY
> implement.
> 
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