Broadband Speed Tests – The Top 3 Incorrect Assumptions


Many websites now offer a broadband speed test. People are naturally curious to see if they are actually getting what they are paying for. In the UK, many broadband providers offer connections that fall short of the expectations that the providers themselves set. The almost mythical “up to..” statement is often a way for broadband providers to tempt new customers at the same time as evading the sticky question of why, on average, most broadband connections fall well short of the advertised speed.

Results from speed tests show that the average speed across all providers in the UK is currently just less than 4Meg. Naturally, people are concerned that they are getting less than 50 percent of the advertised “up to 8Meg” speed and will use on-line speed tests to check their actual connection speeds at various points throughout the day to verify the actual speed being provided.

Whilst many websites offer broadband speed tests, often the results provided are not accurate. Test the Connection Speed of a Server Websites will use “home grown” tools or applications. Whilst there is nothing inherently wrong with “home grown” services, in many cases several incorrect assumptions are made that mean that the test results are not accurate.

The top three common inaccuracies with many “home grown” broadband speed testers are as follows:-

Incorrect Assumption 1:- Inaccurate file size calculations. Some applications simply measure the time it takes to download a file of know size (for example an image file of 500k). The problem comes when doing timing calculations that require calculating bits per second. The correct size of a 500k file (in bits) is 1024 x 500 = 512,000 bits. Many calculations will incorrectly assume that 500k = 500,000 bits. In our example, this leads to an error of several percent.

Incorrect Assumption 2:- Assuming that downloading starts immediately. In timing a download file, many speed test applications will start the timing from when a user clicks the “go” button. The incorrect assumption here is that the download starts immediately. This is not the case as an initial delay is always present when requesting any file from a web server. This incorrect assumption results in additional inaccuracy of the test result.

Incorrect Assumption 3:- Using JavaScript for timing events JavaScript is a scripting language that is supported by most modern web browsers. It is used extensively for applications such as dynamic menus, photo albums and pop up windows. Many applications will use simple JavaScript to time the events (i.e. start and end of download) of downloading a file. The problem with this approach is that, as the JavaScript runs on a user’s computer / web browser, it can be subject to fairly high drift based on a user’s internal computer clock. Using simple JavaScript for testing broadband speeds can therefore further contribute towards inaccurate results. Many websites now offer Flash based tests which look great. However, users need to be aware that, Flash based speed tests are usually just a pretty gloss over the top of simple file downloads, timings using JavaScript.

Writing and providing an accurate broadband speed test requires in depth technical knowledge on networking protocols and cannot be achieved using simplistic JavaScript timing events and file downloads.

Accurate test results can only be achieved from professional quality speed test applications. Many of the more accurate applications for testing broadband connection speeds are highly specialized commercial products developed and supported by software companies with expertise in network monitoring. At the very least, broadband speed testing applications should run on complied language platforms (such as Java). Java allows access to the required elements (such as timers, files and networks) of computer and network that are simply not available using simple web browser scripting (e.g. JavaScript).

To get an accurate idea of your broadband connection speed, it is advisable to:-


  • Run tests at several different times throughout the day. Three tests (For example:- early morning, mid afternoon and early evening) should be sufficient for a decent picture of what is happening.
  • Use tests from several different test websites. Try to find sites with a service located close to you so as to avoid further inaccuracies from Internet network latency or congestion.
  • Use professional tests. Results from many Flash based or “home grown” services are fairly basic and only offer an approximation of your connection speed.

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