[CentOS] Bandwidth limiting and shaping

Hi,

I have a client that is looking for an solution to do bandwidth 
monitoring and traffic shapping.  I would like to use Centos if 
possible, but I need somthing that has a GUI so they can easily make 
changes and updates.  It would have to be ip based or mac address.

What would you suggest.  I have looked a Ipcop and smoothwall as 
solutions so far.

Thanks