Testing network speed with raspberry pi

Posted: by Joe Johnston

This is a quick hack to test the Internet connection speed of your raspberry pi running rasbian linux.

As you may know, I have a small farm of RPIs doing SETI@Home work. I have one head node that all that traffic flows through. This simplifies configuration and makes the farm portal. Here’s an architecture diagram via emacs artist-mode.

                                  +-------+
                             -----+ node1 |
                             |    +-------+
                             |
  +--------+   +---------+   |    +-------+
  | Public |---| Pi Head |---|----+ node2 |
  +--------+   +---------+   |    +-------+
                             |
                             |    +-------+
                             -----+ node3 |
                                  +-------+

I was worried that perhaps the traffic from my six worker nodes was overwhelming the WiFi adapter of my head node. There are two approaches I used to do this.

The first is to look at the performace of short-term bursts. This will give me a flavor for the peak capacity provided by the head node’s built-in WiFi adapter. To do this I need nload (a terminal program that provides histograms of network traffic per adapter) and wget.

I open one terminal and run nload -i wlan0 (I do not use predictable interface names because I am ancient). Then I open a second terminal and run wget to fetch a large file. Fitting, the rasbian image is quite adequate for this.

wget -O /dev/null https://downloads.raspberrypi.org/raspbian_latest

Don’t worry about disk space. This command throws all the fetch data into the bit bucket.

My head node is about 4-6 meters from the WiFi access point in my home. I get about 40 - 45 MBit/s on average from this load. Yes, there are a lot of reasons why the load may be delivered as consistently as in a lab setting, but this will give you a flavor for the capacity of your RPI’s WiFi service.