Network Performance – iPerf and jperf

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I recently setup my new laptop and wanted to test the network connection. I have had some issues with the speed and performance on wireless with the new T410. My home network has both a G wireless and N wireless network available. I have been seeing poor performance on the new thinkpad, while the old T61 would get almost twice the performance. I wanted to test this, and found a great tool iperf to allow me to validate my concern (I have since learned that the wireless cart in the t410 is a bit suspect)

iperf is a little gem to have for testing. It is a network packet generation tool that will allow you to measure bandwidth. It has a server and a client portion.

You can read about iperf here:
I used a quick tutorial from to get the install going. I had 2 cases I wanted to test. My new laptop to another box on the wireless network and my laptop to a pc on the wired network. (both G and N).

First Step was to download the application. I got it from here. (

To run you only need to open a command prompt (start | run | cmd) and change directory to where you saved the file.

I needed to run iperf on both a windows and a linux box. The install for windows is simply download and run the iperf.exe. On linux I needed to grab the latest release. I am running ubuntu so it can simply be done by running

sudo apt-get install iperf

To configure the the server side of iperf you only need to run the command iperf -s (both on linux and windows). To allow this to work on linux I needed to open port 5100. To do this on ubuntu I ran the following command to open ufw.

sudo ufw allow 5100

To test I ran

 iperf -s

on both the ubuntu and my windows pc on the network.
On the client machine, the T410 laptop in my case I ran

iperf -c

(this calls iperf with the client switch and the name of the server to communicate with-
Here are the results of the Ubuntu box on the wireless network

The results were: (6.67 Mbits/sec)
Interval Transfer Bandwidth
0.0-10.0 sec 7.96 MBytes 6.67 Mbits/sec

I then ran the same test to the PC on the LAN directly to the wireless AP. This resulted in 14.8 Mbits/sec

From my test results I can see that using the G network is only getting me about 2Mbits per second. However connecting to a wired pc through the G network results in about 14Mbits per seconds.

To be a bit more robust in testing I had the Linux box run the test to the windows PC as well.

this shows that 2 wireless clients do not get that great of throughput between them.

To round out this post there is also a graphical element to iperf (jperf) it is written java and can be downloaded at Google Code

Once you download and extract the files you can run jperf.bat to launch the application.
Here is a screen capture of jperf running on the Laptop connecting to the Windows PC on the LAN

Overall iperf has been a great tool to help diagnose issues with network latency and bandwidth.

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