network usage software on my gateway

[Mihamina Rakotomandimby (R12y)]

Hi,
We reached a point our internet connexion is overheaded.
We have about 20 workstations.
I would like to build some stats on the network consumption: HTTP, FTP, 
Torrents, Instant messenging, whatever...
The goal is to find out first what kind of traffic is overheading the 
connexion.

Thus, I look for a very good and clever software in order to detect traffic 
kind. I would be only about detecting the working port, because MSN (for 
example) can go through 80 port: I need the soft to detect it's an MSN 
using 80.

What would be your advices?

-- 
                              Chef de projet chez Vectoris
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System: xUbuntu 8.10 with almost all from package install
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