I am evaluating the feasibility of this project. I'd like to be able to establish an encrypted VoIP call between two asterisk PBXs.
I plan to establish a traditional IAX call over an encrypted VPN tunnel between the two asterisk servers. The servers are linked via a traditional analog phone line and are able to dial each other and establish a PPP connection. I got acceptable results when placing the call over the plain PPP link.
However I've been having problems calling over an OpenVPN tunnel. The call goes through but the RTP audio packets are dropped, i keep getting the UDP4 no buffer space available. I've already tweaked multiple parameters and settings on the kernel and openvpn but still does not work.
Does anyone know any other way that this can be accomplished? It should be able to create an encrypted tunnel over two linux servers linked by 2 modems. TCP tunnels are not acceptable as VoIP calls are UDP.