[Linux-cluster] Throttling HTTP traffic when using director ?

[FM]

Hello,
Our setup :
 1 director in front of 4 web servers. (redhat cluster suite). All
servers are behind Pix Firewall

We need a way to stop abusing users (based on a download limit per day
for ex.).
The prob is that we need to do it on the director level (so we cannot
use apache2 modules) and it has to be dynamic based on the bandwidth
usage of the client.

Should I use iptable's traffic shaping capabilities for that ?

Do you have any advice for this particular situation.

Thanks !!

F