MRTG
From MoodleDocs
MRTG: The Multi Router Traffic Grapher
Some large moodle installation (e.g. San Francisco State University) are using MRTG to monitor their network traffic. It could give you very nice daily, weekly, monthly, or even yearly graph of your network traffic (to your moodle site). Here are some examples:
http://www.switch.ch/network/operation/statistics/level3.html
For more information about MRTG:
