Re: [Linphone-users] HT-Proxy and Linphone (HTTP-Tunneling)

[Klaus Darilion]

Am 16.06.2010 15:51, schrieb Mitch Davis:
> On Wed, Jun 16, 2010 at 5:41 PM, Sebastian Wagner<address@hidden>  wrote:
> > I would like to know if there are plans or started implementation for
> > HTTP-Tunneling in Linphone.
> >
> > Anyway: HTTP-Tunneling is a quite common (and comfortable) way of
> > bypassing the firewall
>
> One problem with doing this is that HTTP uses TCP, which is a
> "reliable" protocol.  That is, the protocol doesn't pay special
> attention to getting packets delivered on time, rather, it focuses on
> getting *all* packets delivered, in order.  This isn't a great idea
> when one is carrying live voice, because for time-critical
> applications like voice, it's better to drop a few packets than to
> hold everything up and be 100% reliable.  Most voice and video codecs
> are designed with this in mind, and can somewhat conceal some missed
> packets.
>
> It may be easy to tunnel HTTP, and it may be possible to do live voice
> over HTTP, but in general, HTTP is the wrong tool for the job.

In theory you are correct. But enough bandwidth and some application 
logic can solve the problem - see Skype which can tunnel everything over 
HTTP(S).

SIP over HTTP tunnel should be rather easy to implement. the client only 
has to use SIP over TCP/TLS and connect to the http proxy instead of the 
real target, and then send a CONNECT request before starting with the 
SIP signaling. Of course there might be issues with SRV/NATPR lookups as 
those are of course not implemented by normal HTTP proxies.


regards
Klaus