Limiting bandwidth dynamically in Squid

In fact my problem is with users who download large files from internet in my network.

I have a Squid cache/proxy server in my network that is placed between my network and the Internet.

I thought terminating connections that is alive for a long time maybe helps to prevent users downloading large files. So ask it in SO in this post but didn't get clear answer. it seems it's impossible with Squid. :-/

Now, one solution that also suggested in that post is limiting bandwidth for each user: We just give a suitable bandwidth to each user and user can do anything (even downloading) without bothering others.

But as far as i know Squid can only assign some static bandwidths to users. So any user has a particular static bandwidth that cannot be changed. I seems this is not fair nor optimum, Because in idle situations (when little users are requesting) we should give them more bandwidth than their share in busy situations.

So in a fair system the bandwidth should be divided between available users considering a priority (some users should have more share than others). The share of any user depends on all available users. more users less share. Something like this:

UserBandwidth = (OverallAllBandWidth / NumberOfCurrentUsers)

If in one moment we only have one user, we should assign all bandwidth to him.

So:

• Is this solution possible with Squid?

• Is it possible with any other software? How about Linux itself? I heard about some abilities in linux kernel for traffic shaping.

If it's impractical, what other solution would you suggest in order to:

• prevent users from downloading (specially HTTP downloads)

or

• enforce a bandwidth limit that is fair and certainly dynamic

Thanks!