IP Traffic accounting on a LAN

[Lucas Barbuto <lucas@qk.com.au>]

Hi List,

I'm hoping somebody here can help me.  I've been asked to set up some
IP based accounting so that internet usage can be tracked on a per-user
basis at the office.  I have three problems here:

1)      We have a firewall performing NAT on all incoming and outgoing
        connections

2)      We have an SMTP/IMAP mail server inside the LAN

3)      We run a web proxy on the firewall

So, does anyone know of any (possibly three seperate tools) that will
allow me to log the amount of internet traffic per user?  So far I've
looked at the following tools:

1)      IPTraf for monitoring non web and mail traffic, which seems to
        work OK if I filter out all LAN<->LAN traffic and don't show
        connections by the gateway itself

2)      Eximstats for mail, this rates users by the amount of mail they
        send and receive, but it doesn't discriminate between mail sent
        and received locally and externally

3)      Calamaris and Webalizer for analysing Squid logs, unfortunately
        these don't seem to do analysis on a per requesting IP basis

So basically I'd like to know of tools for Exim and Squid that are
capable of tracking the amount of data that has to be sent and received
from the internet on a per user or per local IP address basis.  I've had
a look around on Freshmeat and elsewhere but nothing's really jumped out
at me.  Does anyone know of a way of doing this?  I'm sure I'm not the
first person to have had this problem.  Any help would be much
appreciated.

Regards,

Lucas