Quality issues

I’m running the most recent Asterisk 1.2 and am trying to improve call quality. I’ve changed to a SIP provider which has a much better traceroute than my old one but it seems to have not helped much. I have a full T1 and no more than 4 calls at once. I have QoS in place. The server runs Slackware 12.0. The CPU is an AMD Sempron™ Processor 2800+ and has 1GB RAM. Codec is g729 and incoming calls are recorded using MixMonitor. Employees are using a combination of Xlite, Linksys/SPA942 and Grandstream ATA. All seem to have the intermittent “choppiness” call quality problem.

I suspect that running other services (squid in particular) on the Asterisk box may be contributing to the quality issues. If that’s a possibility then I could easily move Asterisk to a dedicated box. Before I bother trying however, I thought I’d ask what people here think of my theory. Any thoughts would be appreciated.

Are the calls from internal phone to internal phone also choppy?
What happens if you stop recording?
Does quality improve if you turn off squid (and any other unneeded services).
Is there any non-web based GUI installed or running on the server (x11, kde, gnome etc)? If so turn it off (actually just get rid of it it is well known issue with Asterisk).

Hopefully with the questions above you can start to narrow down if the server or internal network is the issue. If the internal calls are okay the issue most likely with your T1 or SIP provider.

Do you have QoS internally or is it “end to end” with your T1 data provider?
Whats the latency on the T1 line?

I would personnally get rid of squid and any other services as mentioned previously. If you are using the Asterisk server as a proxy for web browsing this will cause issues with voice quality if web browsing uses a lot of bandwidth.