A. Khattri wrote:
> On our side, we would like to look at bandwidth usage of each site over a
> period of time to determine which ones are heavy with traffic and to look
> at the long-term trends. Eventually, it would be nice to manage bandwidth
> and track total usage for billing purposes.

When it comes to network accounting the following may be of interest -
there was a presentation at the linuxtag open source conference:

http://www.linuxtag.org/typo3site/freecongress-details.html?&talkid=131

Network accounting was demonstrated based on the ip_conntrack module in
the kernel. Some new enhancements of ip_conntrack solve some problems
you have with accounting in userspace with single ip_tables rules for
each IP-Address or similar userspace solutions. You don't have the
overhead of transfering huge amounts of data to userspace or getting
endless rulesets as you have with previous approaches.

Sorry, I did not use it myself and I don't know a link to further
information, but searching for ip_conntrack may give some hints.

-- 
Andreas