I have two linux machines m1 and m2 (both totally in my control if that matters), and would like to estimate the amount of ethernet traffic between those two machines. I don't need anything detailed, but just want to get the order of magnitude (e.g. 100 kb/sec vs 1 Mb/sec), ideally with a fine-grained frequency so that I can get some statistics (max/min/avg) over a time horizon.
Typically, something like iostat but for ethernet would be perfect.
This page will give you an overview of iperf and ntop - iperf will allow you to find the max possible bandwidth between the machines, ntop will allow you to measure the actual bandwidth being used. http://www.enterprisenetworkingplanet.com/netos/article.php/3658331/Measure-Network-Performance-iperf-and-ntop.htm