I always like to know what’s going on with my individual systems (especially air-gapped LANs), so if it hangs I have a good idea why. And I especially like to know when lots of data is going out of my systems. So we are going to make a handy little plasmoid which does this very effectively, and will run on KDE, XFCE, LXDE, etc, and given its cmake origin will probably build and run on OS-X and Windows as well.
Here’s what it looks like. (click to enlarge) It sits in your System Tray, and monitors the outward network interface. Green traffic (bottom) is incoming, and red traffic (top) is outgoing. You can set the scale to just about anything, but I’ll give a reasonable default below.