iperf has been around for many years. The most widely used version was iperf version 2, however in the past year or so iperf3 has been available. iperf3 is a complete re-write and not necessarily compatible with iperf2. In theory, for the tests we are performing in the assignment they should be equivalent. However some students have reported strange results, and after I ran some tests with both iperf2 and iperf3, I note some strange results with iperf3. It seems there are some substantial differences between the versions. In summary, I discovered:

• For Ethernet, with both TCP and UDP, iperf2 and iperf3 are about the same. So you can use either.
• For WiFi, with TCP, iperf2 and iperf3 are about the same. So you can use either.
• For WiFi, with UDP, iperf2 looks to be ok, but iperf3 returns strange results (e.g. throughput higher than data rate). I think this is because of packet drops, but it needs further investigation. I recommend you only use iperf2 for WiFi/UDP experiments.

What should you do?

• If you are using iperf2 already, no problem.
• If you haven't performed many experiments yet, I suggest using only iperf2.
• If you have already run many experiments with iperf3, then your results with Ethernet (TCP/UDP) as well as WiFi (TCP) can be used. But you should ignore any results you obtained for WiFi with UDP. You can either run those again with iperf2 or don't use UDP as a parameter.

Below are my results from tests with different versions of iperf and link/protocol options. All tests were on Linux, using iperf 2.0.5 or iperf 3.0.11.

Ethernet - both iperf2 and iperf3 are ok

iperf2, TCP: 934 Mb/s

iperf3, TCP: 933 Mb/s

iperf2, UDP: 535 Mb/s

Although the throughput is quite low, it may be due to other parameter values. At least the result is believable.

iperf3, UDP: 255 Mb/s

Although the throughput is quite low, it may be due to other parameter values. At least the result is believable.

WiFi with TCP - both iperf2 and iperf3 are ok

Note that my WiFi data rate varied from about 12Mb/s to 18Mb/s during these tests. Hence I expect throughput to be less than those values, maybe about half (since there may be other interfering clients nearby).

iperf2, TCP: 5Mb/s

iperf3, TCP: 5Mb/s

WiFi with UDP - iperf2 is ok, iperf3 is wrong

I used a sending rate of 50 Mb/s.

Again, data rates are 12Mb/s to 18Mb/s, expecting similar throughput as TCP.

iperf2, UDP: 5Mb/s

Note the server reports the throughput. The client is reporting a sending rate of 50Mb/s, while the server receives 5.24 Mb/s.

iperf3, UDP: 47 Mb/s

The bandwidth reported at the server is 47Mb/s !!! But the data rate is 18 Mb/s. That is not possible. Note there are very low, per second results (131 kb/s, 0 b/s) and strange results of datagrams lost (-nan). I don't know what is happening in this test, but I do know that the summary bandwidth of 47.7Mb/s is not the throughput. Hence I cannot use these results.