Imagine this scenario. Outside your house, the most awesome super highway has been built. It has a speed limit of 120 Mile Per Hour. You calculate at those speeds you can get to and from work 20 minutes earlier. Life is good. Monday morning comes, you hop in your Nissan GT-R, put on some new leather driving gloves, and crank up some good driving music. Your pull onto the dedicated on-ramp from your house and are quickly cruising at 120 Miles an hour. You make it into work before most anyone else. Life is good.
Near the end of the week, you notice more and more of your neighbours and co-workers using this new highway. Things are still fast, but you can’t get up to speed to work like you could earlier in the week. As you ponder why you notice you are coming up on the off-ramp to your work. Traffic is backed up. Everyone is trying to get to the same place. As you are waiting in the line to get off the super highway, you notice folks passing you by going on down the road at high rates of speed. You surmise your off-ramp must be congested because it is getting used more now.
Speedtest servers work the same way. A speedtest server is a destination on the information super-highway. Man, there is an oldie term. To understand how speedtest servers work we need a quick understanding of how the Internet works. The internet is basically a bunch of virtual cities connected together. Your local ISP delivers a signal to you via Wireless, Fiber, or some sort of media. When it leaves your house it travels to the ISP’s equipment and is aggregated with your neighbours and sent over faster lines to larger cities. It’s just like a road system. You may get access via a gravel road, which turns into a 2 lane blacktop, which then may turn into a 4 lane highway, and finally a super-highway. The roads you take depend on where you are going. Your ISP may not have much control over how the traffic flows once it leaves their network.
Bottlenecks can happen anywhere. Anything from fiber optic cuts, oversold capacity, routing issues, and plain old unexpected usage. Why are these important? All of these can affect your speedtest results and can be totally out of control of your ISP and you. They can also be totally your ISP’s fault. They can also be your fault, just like your car can be. An underpowered router can be struggling to keep up with your connection. Much like a moped on the above super-highway can’t keep up with a 650 horsepower car to fully utilize the road, your router might not be able to keep up either. Other things can cause issues such as computer viruses, and low performing components.
Just about any network can become a speedtest.net node or a node with some of the other speedtest sites. These networks have to meet minimum requirements, but there is no indicator of how utilized these speedtest servers are. A network could put up one and it’s 100 percent utilized when you go running a speedtest. This doesn’t mean your ISP is slow, just the off-ramp to that speedtest server is slow.
The final thing we want to talk about is the utilization of your internet pipe from your ISP. This is something most don’t take into consideration. Let’s go back to our on-ramp analogy. Your ISP is selling you a connection to the information super-highway. Say they are selling you a 10 megabyte download connection. If you have a device in your house streaming an HD Netflix stream, which is typically 5 megs or so, that means you only have 5 megs available for a speedtest while that HD stream is happening. Speedtest only test your current available capacity. Many folks think a speedtest somehow stops all the traffic on your network, runs the test, and starts the traffic. It doesn’t work that way. A speedtest tests the available capacity at that point in time. The same is true for any point between you and the speedtest server. Remember our earlier analogy about slowing down when you got to work because there were so many people trying to get there. They exceeded the capacity of that destination. However, that does not mean your connection is necessarily slow because people were zooming past you on their way to less congested destinations.
This is why speedtest results should be taken with a grain of salt. They are a useful tool, but not an absolute. A speedtest server is just a destination. That destination can have bottlenecks, but others don’t. Even after this long article, there are many other factors which can affect Internet speed. Things we didn’t touch on like Peering, the technology used, speed limits, and other things can also affect your internet speed to destinations.