Internal Program Version: iperf 3.18 (The man files)

Iperf is a tool for active measurements of the maximum achievable bandwidth on
IP networks. It supports tuning of various parameters related to timing,
protocols, and buffers. For each test it reports the bandwidth, loss, and other
parameters. This version, sometimes referred to as iperf3, is a redesign of an
original version developed at NLANR/DAST. iperf3 is a new implementation from
scratch, with the goal of a smaller, simpler code base, and a library version of
the functionality that can be used in other programs. iperf3 also a number of
features found in other tools such as nuttcp and netperf, but were missing from
the original iperf. These include, for example, a zero-copy mode and optional
JSON output.

Note that iperf3 is NOT backwards compatible with the original iperf.

https://software.es.net/iperf