iPerf is an open source, free, network performance measurement tool. It works by simply sending traffic from one host to another and measuring the bandwidth that can be achieved. In addition to the throughput measurement it can give metrics such as packet loss, jitter, and traffic distribution. iPerf works for both TCP and UDP traffic with certain nuances that pertain to the specifics of each protocol.
Versions
There are two versions of iPerf which are being developed in parallel: version 2 and version 3. They are incompatible to each other, and maintained by different teams. However, both have the same set of functionalities, more or less.
iPerf version 2 was released in 2003 and it’s currently in version 2.0.13. iPerf version 3 was released in 2014 and it’s current version is 3.7. iPerf3 is a rewrite of the tool in order to produce a simpler and smaller code base.
The team that has taken the lead in iPerf2 development is mainly focused on WiFi testing, while iPerf3 is focused on research networks. However, most of their functionality overlaps, and they can be both used for general network performance and testing.
Both versions support a wide variety of platforms, including Linux, Windows, and MAC OS. And there is also a GUI version of iPerf2 based in Java, called JPerf.
Usage
In iPerf “lingo”, the host that sends the traffic is called client and the receiver is called server. Here is how the command line output looks for the two versions and for UDP and TCP tests, at their basic forms without any advanced options.
TCP
iPerf2 server
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netbeez.net$ iperf -s ------------------------------------------------------------ Server listening on TCP port 5001 TCP window size: 85.3 KByte (default) ------------------------------------------------------------ [ 4] local 172.31.0.25 port 5001 connected with 172.31.0.17 port 55082 [ ID] Interval Transfer Bandwidth [ 4] 0.0-10.0 sec 1.09 GBytes 939 Mbits/sec |
iPerf2 client
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netbeez.net$ iperf -c 172.31.0.25 ------------------------------------------------------------ Client connecting to 172.31.0.25, TCP port 5001 TCP window size: 85.0 KByte (default) ------------------------------------------------------------ [ 3] local 172.31.0.17 port 55082 connected with 172.31.0.25 port 5001 [ ID] Interval Transfer Bandwidth [ 3] 0.0-10.0 sec 1.09 GBytes 940 Mbits/sec |
iPerf3 server
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netbeez.net$ iperf3 -s ----------------------------------------------------------- Server listening on 5201 ----------------------------------------------------------- Accepted connection from 172.31.0.17, port 56342 [ 5] local 172.31.0.25 port 5201 connected to 172.31.0.17 port 56344 [ ID] Interval Transfer Bandwidth [ 5] 0.00-1.00 sec 108 MBytes 907 Mbits/sec [ 5] 1.00-2.00 sec 112 MBytes 941 Mbits/sec ... [ 5] 9.00-10.00 sec 112 MBytes 941 Mbits/sec [ 5] 10.00-10.04 sec 4.21 MBytes 934 Mbits/sec - - - - - - - - - - - - - - - - - - - - - - - - - [ ID] Interval Transfer Bandwidth Retr [ 5] 0.00-10.04 sec 1.10 GBytes 938 Mbits/sec 0 sender [ 5] 0.00-10.04 sec 1.10 GBytes 938 Mbits/sec receiver |
iPerf3 client
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netbeez.net$ iperf3 -c 172.31.0.25 Connecting to host 172.31.0.25, port 5201 [ 4] local 172.31.0.17 port 56344 connected to 172.31.0.25 port 5201 [ ID] Interval Transfer Bandwidth Retr Cwnd [ 4] 0.00-1.00 sec 112 MBytes 943 Mbits/sec 0 139 KBytes [ 4] 1.00-2.00 sec 112 MBytes 941 Mbits/sec 0 139 KBytes ... [ 4] 8.00-9.00 sec 112 MBytes 941 Mbits/sec 0 223 KBytes [ 4] 9.00-10.00 sec 112 MBytes 941 Mbits/sec 0 223 KBytes - - - - - - - - - - - - - - - - - - - - - - - - - [ ID] Interval Transfer Bandwidth Retr [ 4] 0.00-10.00 sec 1.10 GBytes 941 Mbits/sec 0 sender [ 4] 0.00-10.00 sec 1.10 GBytes 941 Mbits/sec receiver iperf Done. |
UDP
iPerf2 server
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netbeez.net$ iperf -s -u ------------------------------------------------------------ Server listening on UDP port 5001 Receiving 1470 byte datagrams UDP buffer size: 208 KByte (default) ------------------------------------------------------------ [ 3] local 172.31.0.25 port 5001 connected with 172.31.0.17 port 54581 [ ID] Interval Transfer Bandwidth Jitter Lost/Total Datagrams [ 3] 0.0-10.0 sec 1.25 MBytes 1.05 Mbits/sec 0.022 ms 0/ 893 (0%) |
iPerf2 client
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netbeez.net$ iperf -c 172.31.0.25 -u ------------------------------------------------------------ Client connecting to 172.31.0.25, UDP port 5001 Sending 1470 byte datagrams UDP buffer size: 208 KByte (default) ------------------------------------------------------------ [ 3] local 172.31.0.17 port 54581 connected with 172.31.0.25 port 5001 [ ID] Interval Transfer Bandwidth [ 3] 0.0-10.0 sec 1.25 MBytes 1.05 Mbits/sec [ 3] Sent 893 datagrams [ 3] Server Report: [ 3] 0.0-10.0 sec 1.25 MBytes 1.05 Mbits/sec 0.022 ms 0/ 893 (0%) |
iPerf3 server
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netbeez.net$ iperf3 -s ----------------------------------------------------------- Server listening on 5201 ----------------------------------------------------------- Accepted connection from 172.31.0.17, port 56346 [ 5] local 172.31.0.25 port 5201 connected to 172.31.0.17 port 51171 [ ID] Interval Transfer Bandwidth Jitter Lost/Total Datagrams [ 5] 0.00-1.00 sec 120 KBytes 983 Kbits/sec 1882.559 ms 0/15 (0%) [ 5] 1.00-2.00 sec 128 KBytes 1.05 Mbits/sec 670.381 ms 0/16 (0%) ... [ 5] 9.00-10.00 sec 128 KBytes 1.05 Mbits/sec 0.258 ms 0/16 (0%) [ 5] 10.00-10.04 sec 0.00 Bytes 0.00 bits/sec 0.258 ms 0/0 (-nan%) - - - - - - - - - - - - - - - - - - - - - - - - - [ ID] Interval Transfer Bandwidth Jitter Lost/Total Datagrams [ 5] 0.00-10.04 sec 1.25 MBytes 1.04 Mbits/sec 0.258 ms 0/159 (0%) |
iPerf3 client
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netbeez.net$ nbiperf3 -c 172.31.0.25 -u Connecting to host 172.31.0.25, port 5201 [ 4] local 172.31.0.17 port 51171 connected to 172.31.0.25 port 5201 [ ID] Interval Transfer Bandwidth Total Datagrams [ 4] 0.00-1.00 sec 128 KBytes 1.05 Mbits/sec 16 [ 4] 1.00-2.00 sec 128 KBytes 1.05 Mbits/sec 16 ... [ 4] 8.00-9.00 sec 128 KBytes 1.05 Mbits/sec 16 [ 4] 9.00-10.00 sec 128 KBytes 1.05 Mbits/sec 16 - - - - - - - - - - - - - - - - - - - - - - - - - [ ID] Interval Transfer Bandwidth Jitter Lost/Total Datagrams [ 4] 0.00-10.00 sec 1.25 MBytes 1.05 Mbits/sec 0.258 ms 0/159 (0%) [ 4] Sent 159 datagrams iperf Done. |
As you can see, the output format is very similar and both versions gave the same measurements in this example. More specifically, in TCP mode iPerf tries to achieve the maximum possible bandwidth. In the previous example, it almost saturated the gigabit link that connects the two hosts. In UDP mode, you can specify the target throughput, and if you don’t give any bandwidth input value iPerf targets 1Mbps.
This is just an introduction on the basics of iPerf. If you have questions don’t hesitate to ask them in the comments. To explore further by yourself, here is a list of resources that you may find useful:
iPerf2 home page
iPerf3 home page
iPerf Performance Testing on Single Board Computers
Speedtest Comparison: Ookla, NDT, NetFlix, HTML, iPerf
Iperf WiFi: Raspberry Pi 3, ASUS, Hawking, LinkSys & TP-LINK