I need to generate reports showing bandwidth usage broken down by port and protocol, based on all data sent/received over the last x days, in a fairly simple and secure way.
Storing full traffic dumps for later analysis is not an option here for privacy and resource reasons.
Being able to record these statistics in a simple way is important, because eventually I need to be able to combine these stats across all of the servers.
The target machines are running Debian, and minimal solutions would be better as many have below average specs. I have looked at nettop and it seemed like overkill, and I wasn't able to find the breakdown by port and protocol I needed.
Any advice would be greatly appreciated!