If you have an internet connection with a limited monthly bandwidth, then no matter what operating system that you use, having a decent network bandwidth monitor can come handy.
But if you use MS Windows and looking for a simple and a free tool, then “BM2” (=Bandwidth Monitor 2) is also a pretty useful tool. However, it’s not an open source tool plus has a paid version with few additional features.
But for monitoring and saving a history of your network bandwidth usage, the free version is more than enough.
Few main features …
*. Supports monitoring more than one network device/interface. But if you only have a one, then you can click on the “Auto-Detect” button and “BM2” will select the active one automatically. Also displays (logs) network usage per device as well.
*. Saves a history of your network usage (Days, Months, Years).
*. Loads automatically on the system startup (disabled by default).
*. Has a small floating window with live network traffic in graphs.
*. Change the update intervals.
*. Adjust the transparency levels.
*. View data usages in Bytes, Kilobytes, Megabytes and Terabytes.
*. A system tray icon.
It has few other options, but I think these are its major features.
If interested, you can get it from this BM2 home page. Make sure to manually enable the “load on system startup” option from its settings window (disabled by default).