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What is iPerf and how is it used?

Expert Chris Partsenidis explains what iPerf is and how iPerf commands can help you measure your network's bandwidth, delay, jitter and potential for data loss.

What is iPerf, and how do iPerf commands work?

IPerf is a popular network tool that was developed for measuring TCP and User Datagram Protocol bandwidth performance. By tuning various parameters and characteristics of the TCP/UDP protocol, the user is able to enter iPerf commands that will provide an insight on the network's bandwidth availability, delay, jitter and data loss. Here are iPerf's main features:

  • Measures TCP bandwidth
  • Reports on maximum segment size and maximum transmission unit;
  • Support for TCP Window size;
  • Multithreaded for multiple simultaneous connections;
  • Creates specific UDP bandwidth streams;
  • Measures packet loss;
  • Measures delay jitter;
  • Runs as a service or daemon; and
  • Runs under Windows, Linux OSX or Solaris.

IPerf is a command-line program that accepts a number of different options, making it very easy to use. Find a full list of iPerf commands by simply entering the following command (Windows version):

C:\> iperf.exe --help

The general idea is to run iPerf on two computers; one acts as the server, while the other takes as the client.

To set up the server side, enter the following iPerf command:

C:\> iperf  -s


Server listening on TCP port 5001

TCP window size: 64.0 KB (default)


This runs iPerf in server mode and will wait to accept the client's connection before it begins the bandwidth tests. Windows users who experience problems might need to run the DOS prompt (cmd.exe) in Administrator mode.

On the client side, initiate the test stream using the following command, assuming the server is configured with IP address

C:\> iperf -c


Client connecting to, TCP port 5001

TCP window size: 64.0 KB (default)


[  3] local port 56023 connected with port 5001

[ ID] Interval       Transfer     Bandwidth

[  3]  0.0-10.0 sec  4.84 GB  4.15 GBps



Once the test is complete, iPerf will display the end results on both server and client sides.

You can explore iPerf further by testing the various options it offers. It is freely available and you can download iPerf at SourceForge.  

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This was last published in December 2016

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