The term bandwidth refers to how much data can be moved at one time from a web server out onto a network and across the Internet. You can think of bandwidth as the diameter of a water pipe. The bigger the diameter of the pipe, the more water you can move, even if the water is moving at the same speed.
POTS (Plain Old Telephone Service) = 64000 BPS (Bytes per second)
ISDN (2 POTS) = 128000 BPS
T1 = (12 ISDNS) = 1,544,000 BPS
Ethernet = (~ 6.5 T1s = 10,000,000 BPS
T3 (28 T1s) = 43,232,000 BPS
FAST ETHERNET (~ 65 T1s) = 100,000,000 BPS
OC3 (3.6 times T3) = 155,000,000 BPS
OC12 (4 times OC3) = 622,000,000 BPS
OC48 ((Internet2) 4 times OC12) = 2,075,136,000 2.4 Gbs/second
OC192 (4 times OC4
= 9.6 Gbs/second
Data transfer (AKA bandwidth usage) refers to how much data/information is sent to or received over a specified period of time. Use the following to determine your monthly data transer:
[Average size of your web page(s) + any graphics included within] * [number of visitors you expect each day * number of pages each visitor will view] * [30 days in a month] = Total Monthly Data Transfer Usage.
If you really want the formula for figuring out the bandwidth of the diferent media, let me know, I'll dig through my books from when I worked for the Telco, but off the top of my head I just cant seem to remember and at the moment cannot find my book LOL