An simplified example. Lets say I have a direct T1 between A and B. A starts to transfer 4 GBytes from B to A and uses 100% of the bandwidth. Then B starts another transfer of 4GBytes from A to B. Both now use 50% of the bandwidth and each transfer takes twice as long.
I can still telnet between the two locations, even play quake - the load is hardly noticable for short transfers.
Since a T-1 is symmetric, wouldn't the transfer take approximately the same time whether A to B or B to A are both or individually transfering files (as long as they are going opposite directions??) So does the cost per byte get cut in half even though the price charged may stay the same ? If ROI is calculated on a 1-way model [ignoring ACKs] they with full duplex utilization ROI = PRICE - COST; ROI'=ROI+PRICE for full duplex operation.
That was my point. Why charge a higher _recurring_ fee for a faster connection?
Because (usually) there is a higher recurring potential traffic load from your site. What if you run one of the big Olympic or Superbowl web sites? And you get charged $1000 per month whether you have a 155Mbit connection or a 56Kbaud connection. Two months out of the year you could fill it, and the other 10 do nothing but send some email. The network you connect to has to be engineered for those peaks or they are not doing their job [IMO]. Granted, we usually talk about mid day peaks, etc, but what about convention halls that might keep a T3 or two around for big trade shows and only *really* use them on the weekends or weeknights or something. Their total (average, or even byte) traffic might not be that significant, but their bursts could be wildly high. -Deepak.