With developments in the area of networks and communication, especially with the introduction of optical fibres, broadband speeds have reached great heights. Accompanying these speeds are also the demands for higher broadband speeds by internet users. These demands have resulted in an extremely competitive market for the Internet Service Providers (ISPs), while also giving birth to many websites that analyse broadband speeds. Among these websites, Ookla's speedtest.net has gained immense popularity for giving a sound analysis of Internet speeds for users worldwide.
While these websites themselves call the tests as just 'estimates' and are not completely accurate, the results they give in most cases are fairly close to the actual speeds. The inaccuracy can be accounted for the way these websites measure speeds and also the configuration of the computer that the network is being tested upon. To better understand what the speed tests signify, we need to understand how these websites measure speeds.
Most of these websites show three different types of results,
2. Download speed
3. Upload speed
Latency is defined as the time elapsed between a message being sent and received by the user. To measure this, the website sends a message from the user's computer to a server (owned by the website). The server, upon receiving this message, sends a reply back to the user. The time elapsed between sending and receiving the message is measured and displayed in milliseconds (ms).
Download speed is the average size of data that can be received by the user over a unit of time. The client requests the server to send chunks of data. During the initial period of the test, the client determines how many connections to the server will result in maximum usage of the bandwidth. After a certain amount of time, the client stops sending requests and the average download speed is measured. It is usually measured in Megabits per second (Mbps).
Upload speed is measured in a similar way as the download speed, except the client sends chunks of data to the server.
The most trivial reason for the inaccuracy is that we never really use the Internet the way these speed tests use it. When we are browsing, we download small HTML pages. When we use video conferencing, we are downloading as well as uploading data simultaneously. Skype, BitTorrent and other P2P applications depend upon other users for data transfer and therefore your speed will not just depend upon the speed your ISP provides, but also the internet speeds of other online users. The traffic activity in all these cases will differ from the sort of activities the broadband speed tests consider while measuring your internet speed. The only case that comes close to what these websites consider as network activity is when you are downloading a single file from a single server.
Another factor that affects these numbers is that your computer might be running background or concurrent activities that use some network bandwidth for downloading updates. This can drastically reduce the download and upload speeds shown by the speed test as the number of connections that can be made to the server for measuring speed is reduced. The results will not include the speeds that could have been achieved, had the background activities not been using the network.
The results shown by these websites will also depend upon the location of the server used to test your broadband speed. If the server is located overseas, the speeds will be very low as data transfers will involve at least one trans-oceanic link which will prove a bottle-neck for the data transfer. In comparison, a server located closer to the user will give higher latency and higher download speeds on the same network.
With the popularity of these websites rising, the test servers used by them are facing higher traffic. When faced with high traffic, most servers will have to delay the response to the users by forming queues, hence reducing the speeds shown to you. Such reductions in speeds are not due to the network you are on, it's because of the delays caused by the test server.
There are many other factors which affect the download speeds minorly such as the presence of proxy servers in corporate networks, heavy traffic faced by your network provider etc.