Video conferencing

? your question is wrong formulated.

the bandwith requiered for videoconferencing depends on the quality and of the sound and video of settings of your program. using netmeeting as a example; go to tools, options video.
A bigger window needs more bandwidth, a smaller video frame requires less bandwith as well as faster video (less pixel, less quality, less bandwidth) vs good quality (more pixels) requieres more bandwidth.

Of course the bandwidth that your are getting is provided by your ISP (if we are talking video conferring over the internet) . Now it depends of course how many users are going to do to the videoconfering you will need 128K or higher bandwith from your ISP.
In a internal network that should not give any problems since it's on your network which is running at 10 or 100MB.

Hoping to have answered some of the questions.

Leopold