I put in a fancy new router and switch and was trying to diagnose local network issues. Discovered iperf for testing between my Synology and wifi Mac, but also discovered that networkQuality can run a server on one Mac and query from another Mac. Led to some interesting results.
@ttscoff I need iperf every few months when the ISP erroneously and automatically resets service limits after maintenance. Luckily, Tier 3 support knows me by now.