Speed tests are a quick way to see just how fast your internet is. ISPs promise “up to” a certain speed in optimal conditions, but a speed test will confirm how fast—or slow—your connection is.
What is a Speed Test?
An internet speed test is the best way to get an idea of how fast your connection is right now. The service you connect to often limits your download and upload speeds based on the plan you chose, local congestion, any throttling rules it has, and so on.
The catch is the promises your Internet Service Provider (ISP) makes nearly always include the phrase, “up to.” This gives an ISP wiggle room—if it promised you “up to 30 Mbps,” and you consistently only get 28 Mbps, then the company can say it’s kept its promise. But if you see 10 Mbps, then you’re not getting what you pay for, and it’s time to call your ISP.
A Speed test measures your ping, and download and upload speeds. Measuring the latter two is essential because most ISPs make separate promises for download and upload speeds. Usually, the download speed features prominently, but if you dig into the details, the ISP typically specifies a slower upload speed for each level. For instance, our local ISP offers a plan with a 500 Mbps download speed, but 125 Mbps upload speed.
How a Speed Test Works
When you start a speed test, multiple things occur. First, the client determines your location and the closest test server to you—this part is important. Some versions, like Ookla’s Speedtest.net, have an option to change the server. With the test server in place, the Speed Test sends a simple signal (a ping) to the server, and it responds. The test measures that roundtrip in milliseconds.
After the ping is complete, the download test begins. The client opens multiple connections to the server and attempts to download a small piece of data. At this point, two things are measured: how long it took to grab the fragment of data, and how much of your network resources it used.
If the client detects you have room to spare, it opens more connections to the server and downloads more data. The general idea is to tax your internet connection and see how much it can do simultaneously.
Imagine your internet service as a highway with a speed limit. Opening additional connections is like adding more lanes to the highway. The speed limit hasn’t changed, but more cars can pass through the same space at a faster rate; thus, the 50th car will arrive sooner using a four-lane highway than it would on a two-lane.
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Source : How Do Internet Speed Tests Work? (and How Accurate Are They?)
