iperf2 was orphaned in the late 2000s at version 2.0.5, despite some known bugs and issues. After spending some time trying to fix iperf2’s problems, ESnet decided by 2010 that a new, simpler tool was needed, and began development of iperf3. The goal was make the tool as simple as possible, so others could contribute to the code base. For this reason, it was decided to make the tool single threaded, and not worry about backwards compatibility with iperf2. Many of the feature requests for iperf3 came from the perfSONAR project (http://www.perfsonar.net).
Then in 2014, Bob (Robert) McMahon from Broadcom restarted development of iperf2 (See https://sourceforge.net/projects/iperf2/). He fixed many of the problems with iperf2, and added a number of new features similar to iperf3. iperf2.0.8, released in 2015, made iperf2 a useful tool.
As of this writing (2017), both iperf2 and iperf3 are being actively (although independently) developed. We recommend being familiar with both tools, and use whichever tool’s features best match your needs.
A feature comparison of iperf2, iperf3, and nuttcp is available at: https://fasterdata.es.net/performance-testing/network-troubleshooting-tools/throughput-tool-comparision/
iperf3 is not officially supported on Windows, but iperf2 is. We recommend you use iperf2.
Some people are using Cygwin to run iperf3 in Windows, but not all options will work. Some community-provided binaries of iperf3 for Windows exist.
-w2Mto increase the socket buffer sizes. That seems to make a big difference on some hosts.
On Linux, run this command to see the available congestion control algorithms (note that some algorithms are packaged as kernel modules, which must be loaded before they can be used):
--logfileoption. How do I see file output in real time?
See the following pages on fasterdata.es.net:
Searching on the Internet is a good first step. http://stackoverflow.com/ has a number of iperf3-related questions and answers, but a simple query into your favorite search engine can also yield some results.
There is a mailing list nominally used for iperf3 development, firstname.lastname@example.org.
We discourage the use of the iperf3 issue tracker on GitHub for support questions. Actual bug reports, enhancement requests, or pull requests are encouraged, however.