If you have X number of minutes of call and you are going to send it to someone to carry on their network, how do you make sure the person has enough Bandwidth to carry the minutes you are sending him? Is there a formula that allows you to calculate the amount of bandwidth needed for the number of minutes you want to send?
calculate 12-15 kb per call.You could go a little bit lower with quintum tenor on both ends and packet saver, but no more than 30% less.
for a T1 worth of calls, 360 kb.
If it was me, I will not go for less than 512 kb to be sure (on the U.S. bandwith is a lot cheaper and easier to get than most places)