hup, following description was also submitted to apple before...
How many bandwidth is actual required for 8kbps G.729 channel? How many channel I can run on the E1 link? Here are the answers, VoIP Bandwidth Calc is a calculator designed to help voice network engineer to calculate how many bandwidth is required for VoIP Channel. You can select different codecs, different voice payload size, Layer2 network type, number of concurrent channel and compressed RTP enable or not and VoIP Bandwidth Calc will tell you how many bandwidth will be actual required for voice channel.