How to improve call quality between 2 Asterisk Servers?


I have 2 asterisk servers. One is here with me in Japan and the other is in Philippines. Basically the 2 servers are connected via IAX and the 2 servers are able to place calls with each other. We have used several softphones but now we are using Cubix Firefly.

The call is stable but the voice quality seems to have a walky-talky effect in the sense that it’s not as clear as what a normal VOIP call should be. I mean I can understand what the other person is trying to say but the sound is not crisp compared to other VOIP services like Broadvoice or Lingo (both I have used using TA’s).

My question is, is there a way to improve the quality of the call? or is this the quality that is expected from a softphone? We use GSM protocol.

I hope you can enlighten me with this question

do you have the IAX jitterbuffer enabled?
have you tried any other codecs?
what kind of bandwitdth do you have available on both ends?

is there any way you could open a VPN connection and tie the servers together over that??? (as a test - VPN tunnels are given priority on some networks, which could lead to less overall latency and better sound quality).

I have two Asterisk servers, one in Barcelona and one in Miami, connected via IAX2. Calls between these two servers are usually better than a ITSP VoIP to PSTN call. The servers are connected via a VPN. We use high quality (Cisco or Nortel) hardphones and the alaw codec since our bandwidth allows. Softphones and gsm could be major reasons for walkie talkie sound.

I have a question. At a networking/Internet level, why would a VPN connection between two server be any more effecient than a public IP to public IP connection? I mean, the traffic travels over the public Internet, so there are not QoS advantages. Or are there?

i’ve read (this has not been confirmed) that certain switches/networks on the internet will prioritize VPN traffic.

also, since you have a dedicated “tunnel”, you have lower packet loss and fewer collisions. if your normal network path is not very clean, then opening a VPN connection may help.

again, this is just what I have read, but it makes sense if the circumstances are right…