How Do I Limit The Bandwidth Each User Can Use From Our Organization S Server

I want to know is there any way to limit the internet bandwidth from server (without applying policy on clients so that they do not be able to install soft wares)?

For example: Each user should be able to use 20 Kbps connection at a time. If the user is not present his quota should be given to another user. The user should not be able to use more that his specified quota. If we have specfied 20 Kbps he/she should not be able to user 21 Kbps even with download managers.

Possible?