What is iPerf and how is it used?

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

Can you explain what iPerf is and how it is used?

IPerf is a popular network tool that was developed for measuring TCP and UDP bandwidth performance. By tuning various parameters and characteristics of the TCP/UDP protocol, the user is able to perform a number of tests that provide an insight on the network's bandwidth availability, delay, jitter and data loss.

It is freely available and you can download iPerf at SourceForge.  

Here are iPerf's main features:

  • Measures TCP bandwidth 
  • Reports on maximum segment size / maximum transmission unit
  • Support for TCP Window size
  • Multi-threaded for multiple simultaneous connections
  • Creates specific UDP bandwidth streams
  • Measures packet loss
  • Measures delay jitter
  • Runs as a service or daemon
  • 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 options 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 the roll of the client.

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

C:\> iperf  -s


Server listening on TCP port 5001

TCP window size: 64.0 KByte (default)


This runs iPerf in server mode and will wait to accept the client's connection before it begins the bandwidth tests. Windows Vista, 7 and 8 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 KByte (default)


[  3] local port 56023 connected with port 5001

[ ID] Interval       Transfer     Bandwidth

[  3]  0.0-10.0 sec  4.84 GBytes  4.15 Gbits/sec

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 has. I'm sure you'll find it a rewarding and enlightening experience.

Good luck!

This was last published in April 2013

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