We use the G.711 codec, which for VoIP will give the best overall quality.

Since it uses no compression and is essentially the same codec used by the PSTN network and ISDN lines, it sounds just like using a regular or ISDN phone. It also has the lowest latency (lag) because there is no need for compression.

From a bandwidth perspective, it can use up to 84kbps (when you factor in all TCP/IP overhead).