Amer Neely
Web Mechanic

What is Bandwidth?

This may be one of the most popular terms used to describe Internet services, and yet I bet most people couldn't give you a good explanation of what it is.

So, if you already know what bandwidth is, just skip over this post and go do something useful. If not, or you just maybe want to make sure you really have an understanding of it, read on.

For most of us, the most important factor in measuring Internet activity is speed. How fast can I download music files; how fast can my favourite web site load. Another term for bandwidth is 'throughput'.

Let's back up a bit first, and consider what the Internet is. As the term implies, it is a network. But a very special network - it is a network of networks. In other words, lots of computers hooked up to other computers.

Now you may think that when you are viewing a web page, or downloading a music file, that it all comes to you in one connected stream of data.

Uh uh. What really happens is more magical than that. The data that you requested is broken up into little packets called, well, data packets. These data packets contain the shipping address, the receiving address, a number designating its sequence in the whole shipment, plus the payload, or the actual data. A lot of stuff packed in there (there's actually more stuff than that but we can skip that). Now the truly magical part is they can each take a different route to get from the shipper to the receiver! Yup, you heard right. Each one of them may take a different route to get to your computer.

OK, keep that picture in mind for the next step. Lots of little separate packets whizzing around all connecting up finally and putting themselves in the same order they left in.

Now, consider what speed is. Speed is how fast something gets from point A to point B. However, there is a very subtle bit of semantics at work when we discuss speed in the context of downloading files or web pages. One good way to think of the Internet is as a network of highways or pipes. Some are great 20-lane autobahns, while others are secondary 2-lane roads. Most might be considered 8-lane highways. As might be expected, the huge wide-track ones connect major points, much as our national highway system. As you move 'downstream' from one of these major points, the highway gets a bit narrower, since it's not moving as much traffic. During the last stretch to the final destination, it may be one of the 2-lane tracks. Now apply that analogy to the Internet and you have a very good picture of how things are connected.

Let's say you have a shipment (music file) that you need to deliver to point B (your home computer). It takes 8 trucks (packets) to handle the complete shipment.

If you have a 4-lane highway and an 8-lane highway, and you set a fleet of 8 trucks off at the same time on both of them, all travelling at the same speed, and going to the same destination, what happens? Well, on the 4-lane highway, the first 4 trucks arrive at the same time as all 8 trucks on the 8-lane highway. The ones on the 8-lane highway have just delivered your whole shipment. Which highway delivered your shipment fastest? The 8-lane highway of course. But all the trucks were travelling at the same speed. This points out the difference between bandwidth and speed. More bandwidth gives the impression if higher speed. Or a fatter pipe delivers more water than a skinny one, when speed is equivalent for both.

There are other technical things that can be discussed here like latency, but I'll leave that for another post. Maybe. Hopefully this gives you a better idea what bandwidth is, so you can actually understand and take part in a conversation about it.

Until next time, happy trails, and keep on truckin'.