[asterisk-dev] Asterisk dialup connection?

[Hans Witvliet]

On Mon, 2010-08-23 at 07:28 -0500, Tilghman Lesher wrote:
> On Monday 23 August 2010 05:02:12 hadi motamedi wrote:
> > Excuse me, You mean the frequency spectrum of the V.90 modem can pass
> > through an G.723.1/G.729a codec w/o much distortion? If so, can you please
> > let me know why my dial up connection cannot get through when
> > G.723.1/G.729a codec is selected?

very good question....
> 
> Neither of those are loss-free codecs.  They are not mere compression codecs;
> they both REMOVE parts of the signal that are not distinguishable by the human
> ear when it comes to speech.  That is the method by which they obtain such
> good compression ratios.  

Fully agree
> Unfortunately for your purposes, the codecs are
> removing exactly the parts of the signal that allow a modem negotiation to
> succeed.
> 
That's odd. Modem nogotiation is only done during setup-phase, not
anymore afterwards...

> It is, however, rather bizarre that you want to be able to do this.  By the
> time they are connecting over a voip connection, they already have access to
> the IP network.  Why in the world would you want to tunnel a modem over IP?
> 

However, if it is correct what you write, the O.P. could deploy an vpn
(either ipsec or openvpn) after the modem-connection is setup and
stable. And feed his voip connections through the vpn, as the
characteristics of the payload of the vpn is hiddem from the modem...

Might be worthwhile to turn off any compression in ether the vpn or the
modems inorder to decrease additional latency.