Tip #12: How fast is your Internet, really?

Have you ever heard broadband reseller agents (the people who stand at booths promoting Streamyx / P1 / Celcom Broadband etc) say that you can subscribe for "one megabyte per second" download speed? And when you bring the modem home and managed to get on the Internet to download something, you notice the fastest you can download is at around 100-120 KB (kilobytes) per second. Why, why, why?

If you look at the piece of brochure or promo material (the one on the right is taken from P1's website), you should see that the speed is quoted as 1 Mbps or 1 Mbit/s (note that the 'b' is not capitalised). The reseller agent was wrong for sure, to have said "one megabyte per second" - it is actually one megabit per second.

One byte (capital B) is equivalent to eight bits (small b). Therefore a bit is 1/8 of a byte. Broadband speeds are advertised in kilo- or megabits per second. And since your computer calculates download speed in kilobytes per second:

1 megabit per second × 1,024 = 1,024 kilobits
1,024 kilobits × 1,024 = 1,024,576 bits


1,024,576 bits ÷ 8 = 131,072 bytes


131,072 bytes ÷ 1,024 = 128 kilobytes per second

Broadband speeds are usually advertised in pairs of download and upload speeds, also downlink and uplink. Downlink is used for downloading, uplink is used for uploading. Typically, the uplink is half or less than the downlink. A good example to highlight this, is that uploading a photo usually takes longer than downloading a photo to view.

To sum things up:

1. Broadband Internet speeds are always advertised in bits per second, e.g. kilobits per second (kbps), megabits per second (Mbps, the M must be capitalised to differentiate from milli).
2. To convert bits per second to bytes per second, divide by 8.
3. Capitalisation of the B in data units matter! A capital B represents bytes (commonly used in computer storage), a small b represents bits (commonly used in networking). Always take note of this when discussing in forums, chatrooms etc, it can get ambiguous in some cases.

In practice, it is nearly impossible to achieve the advertised speed, as most providers deliver their service on a best effort basis. The speed advertised is also exclusive of overheads caused by factors such as interference as well as the way the Internet is designed. There is one exception, such as in my case, whereby I have subscribed to TM's 1.0 Mbps Streamyx package, however results from Speedtest.net always say that I have 1.5Mbps, or sometimes even more! (I believe this also applies to most other subscribers, especially those who reside in newer areas)