We have been using Asterisk at the office for about 4 months. We are using a 15 Channel PRI (ISDN30). We are using Cisco 7940 & 7960 handsets with firmware 7.4. The solution works great, and is rock solid.
We have IPSEC VPN to the directors houses, using routed technology. The home offices are using 256k/1024K ADSL.
We have tried Linksys (no qos), Draytek (with packet prioritisation), Cisco and several other DSL routers.
If we use the Cisco 79xx from home over the VPN we get very bad voice quality problems. It happens if we are dialing out using the ISDN trunks, or calling another SIP phone in the office. Sometimes the call is very clear, but you never know when the Dalek’s are gona get ya!
The echo and distortion is very difficult to describe, so I recorded it on my mobile for anyone who is interested
We have purchased and installed the G729 codec from Digium and the remote handsets have been configured to use this codec.
The problems occur just the same with G729 or G711.
I have read much and tried lots before posting here
Any pointers welcome…