How should I track and save the bandwidth usage of month

Question

Let's say you have a monthly plan with 400GB bandwidth.
How do I track how much bandwidth each visitor in a website takes and save it.

Answer 1

If I understand your desire correctly, I'm concerned you may have to use packet inspection to track clients above the PHP application layer.

You could try to match SNMP / trap data from your networking hardware with webserver session data, but I think it would be easier if you just added a 'fudge factor for transport/protocol wrappers" on top of the more easily-correlated app layer / webserver counters (e.g., from enhanced inet daemon logs).

I'd link to programming-related suggestions but clarification on "what is the trackable data, exactly" would help narrow down a suggestion.