Troubleshooting client speed and traffic shaping using Jperf

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Jperf is a free Java-based GUI tool that performs all the functions as Iperf for those who prefer graphical output and point and click functionality. Jperf is a very useful and trustworthy tool to measure throughput and jitter between two devices in your LAN or WAN. Most online speed tests like speedtest.net or speakeasy.net are not highly accurate because they introduce considerable delays and uncertainty to the measurement. Factors like test server location, concurrent Internet activity, and/or proxy server participation can affect the online test results due to the additional network activity added to the measurement. Using Jperf allows to have an unbiased measurement of your LAN and WLAN throughput with no delays added by uncontrollable variables. This article describes how to install and use Jperf to test data throughput accurately.

Prerequisites: To run this test you will need two networked computers which have access to each other through your local LAN/WLAN. Java must be installed and supported in both computers.

Test scenario

This article describes how to test wireless and wired throughput between two hosts interconnected by a Meraki AP and switch. One of them is connected via wireless access, the other one is connected via wired access. Please refer to the diagram below.

Diagram of jperf test for a wireless client measuring throughput to the wired network

Procedure

1) Download the Jperf (for Windows).

2) Extract the Jperf file in your desktop.

3) Open the Jperf folder and execute the jperf batch file (You need Java installed in your workstation).

Screenshot of Windows Explorer directory locating the jperf batch file

4) The following GUI is going to open. Repeat this procedure in the two workstations.

Screenshot of the jperf application with default configuration

5) On host B (server), please select "Server" under "Choose iPerf Mode". the "Listen port" by default is 5001. You can change it as desired. Click on "Run Iperf".

Screenshot of the jperf application with custom port selected

Note: When prompted, please allow inbound access to the Iperf server ports in Windows firewall.

Screenshot of Windows Firewall Prompt to allow inbound traffic

6) On host A (client), please select "Client" under "Choose iPerf Mode". Specify the server's IP address and port (default port is 5001). Click on "Run Iperf".

Screenshot of the jperf application with 'client' IP configured

7) You will get a Bandwidth and Jitter graph. A command output is also available with the test results.

Screenshot of the jperf application with bandwidth/jitter results