Re: [BEHAVE] [rtcweb] FW: New Version Notification for draft-chenxin-behave-turn-websocket-00.txt

["Hutton, Andrew" <[e-mail]>]

I agree with Bernard's comments regarding the impact of DPI but of course such DPI devices do what they do and we can't and even don't want to stop them from doing it. However for the case when policy is such that the firewall will only allow traffic to traverse that comes from the HTTP Proxy or a network specific TURN server and there is no deliberate policy to block WebRTC media we need a solution and this is what draft-hutton-rtcweb-nat-firewall-considerations-00 addresses.

So far I don't see the benefit that TURN over websockets would have in this scenario and it needs additional implementation in the browser and the TURN server.

Regards
Andy


> -----Original Message-----
> From: Bernard Aboba [mailto:[e-mail]]
> Sent: 15 May 2013 18:20
> To: Hutton, Andrew; Chenxin (Xin); [e-mail]; [e-mail]
> Subject: RE: [rtcweb] FW: New Version Notification for draft-chenxin-
> behave-turn-websocket-00.txt
> 
> Andrew Hutton said:
> > When we wrote the draft http://tools.ietf.org/html/draft-hutton-
> rtcweb-nat-firewall-considerations-00 we did not include this option
> because we did not see the benefit of additional transport options for
> TURN given that the existing options (E.g. TURN/TCP and TURN/TLS) seem
> to be meet our needs.
> >
> > So what would be the benefits that justify this addition transport
> option for TURN?
> 
> [BA] In my experience,  institutions with very restrictive security
> policies (e.g. those that don't allow UDP in or out) also tend to
> deploy other measures such as deep packet inspection.   So just because
> some traffic is allowed in or out on port 80 does not mean that
> TURN/TCP will be allowed on that port - a DPI box may examine the
> traffic and complain if it doesn't see HTTP being used.  On the other
> hand, unless the DPI box is upgraded, it will also complain about
> websockets.  So I think draft-chenxin only helps in a situation where
> TURN over Websockets would be allowed when TURN/TCP would not be.  That
> scenario is rare, at least at the moment.
>
> The argument for TURN over Websocket/TLS is even more difficult to
> make. While DPI boxes may examine traffic destined to port 443
> carefully to make sure that TLS is really being used,  assuming that
> the DPI box does not see anything it considers fishy, the TLS exchange
> will complete and the DPI box will lose visibility.  After TLS is
> running, the DPI box does not have much information available to
> distinguish TURN/TLS from HTTP over TLS, with or without websockets --
> and those things it does have (such as packet size) are as likely to
> result in an objection to websocket transport as TURN/TLS.  So I'm not
> sure that draft-chenxin will help in that situation either.