Use G.729 if the calls terminating on Unity will be traversing the WAN. G.729 uses 8kpbs per call, though the actual bandwidth used can effectively be as much as 20kbps and theoretically as high as 35kbps. I've never seen anything higher than 20kbps per call. I plan on 12kbps per call and then measure call bandwidth and adjust the WAN link accordingly.
Use G.711 if all calls terminating on Unity only traverse the LAN. G.711 uses 64kbps per call, and it can theoretically be higher than that, though I don't bother myself with the bandwidth since the only potential bottlenecks are badly configured switches.
Yes, G.711 sounds better than G.729, but I know the Mean Opinion Score (a measurement of how good people think calls sound) for G.729 isn't shabby at all (around 3.5??). It is on par with a decent cell phone call.
Related to this is codecs for other voice apps. Unity is the only voice app by Cisco that supports G.729, to my knowledge. If you are using any other voice apps whose calls terminate on devices across the WAN, you'll need to get a DSP farm that translates those codecs for you. DSP farms fit into network modules in routers and gateways such as the VG200. And they cost a lot, but less than the price of a bigger pipe.
Brandon
Brandon
