[CentOS] Lan Monitoring Software on Centos

hey friends,

 I am looking for a free Lan Monitoring Software/tool on Centos. My
Network is hetrogenous consisting of   Windows XP/2000/2003/98, Pix
Firewall, APC UPS, Printers , Laptops.


I want to monitor Desktops & Laptops and want a daily, weekly,monthly
reports for each and every client with the details like Bandwidth
spend on www, mail, chatting. Company wants to track how much
bandwidth each client is consuming and on what.

Is there any such tool available? I am using Centos 4.0


Thanks & Regards

Ankush Grover