Iperf here is a means of measuring networks - capacity & latency (including dual queue L4S) over sockets both TCP and UDP. The goals include maintaining an active iperf code base across a broad set of platforms and operating systems. This is a multi-threaded design that scales with the number of CPUs or cores within a system. It supports both high impact and low impact techniques to obtain and report network performance.

About iperf 2 and iperf3: Read about the differences between these programs at
https://iperf2.sourceforge.io/IperfCompare.html