Technical Terms: Bandwidth

The term Bandwidth is used to describe data transferred over time. However, it is often misused to define a limit on total data transfer. Bandwidth is measured in bits per second, usually using kilo or mega-bits to make the numbers more reasonable. Marketing departments often distort bandwidth to only show maximum or one-sided numbers.
Video Transcript / Captions
Closed captioning for this video is available on YouTube: Technical Terms: Bandwidth.

So let's take a look at the term Bandwidth. Undoubtedly this is a term that you've heard before but maybe you haven't thought about exactly what it means. A lot of people do misuse it.

What bandwidth really is, is the amount of data over time. In that way it's kinda similar to when you say speed which is the reason why we sometimes use the word speed instead of bandwidth. Speed is distance over time and bandwidth is data over time. So let's take a look at some speeds that we've dealt with in the past.

Dialup modems, if you remember those, usually ran around 56 kilobits per second. So that's kilo, as in thousands of bits and bits are either ones or zeros per second. That's the speed that we had of transferring data using modems. If you used ethernet cables to connect computers, as we did before WiFi, then you were usually doing speeds about 10 megabits per second. So megabits being a thousand kilobits and you were doing ten of those on old style ethernet. Ethernet then went to 100 megabits per second and it's now at a 1000 megabits per second typically.

But usually we use WiFi nowadays to network our computers. That runs at about 600 megabits per second. That's using 802.11n. Older versions of WiFi will be slower and newer versions will be even faster than that. Now if you're using mobile phones and mobile connection then you might be using LTE network which is typically the faster networks now. They run at 12 megabits per second. But 5G, which is in the future, will be running many times faster than that. Some estimate it at around 490 megabits per second. Almost as fast as WiFi in our homes from computer to computer.

So that gives you some idea what we're talking about. Now let's take a look at these units just so you understand them. You know kilobits, sometimes using kbps especially when talking about mobile, that's a thousand bits. A bit is a one or a zero. Megabits, mbps, is a thousand times that. Now a lot of times when you have 1000 megabits per second providers like to call that gigabit although my provider calls 100 megabits per second gigabit ethernet or gigabit bandwidth.

Just to give you an idea of what that really means is every byte has 8 bits. We usually do a byte as a single character, like a letter in a word processing document. An image file typically averages around 2 megabytes. So 2 million bytes. So you can kind of figure how long it would take to download. It takes a fraction of a second over a gigabit connection, for instance, to download an image. You know, maybe a second or so over mobile to, you know, a full high level resolution image. A lot of times when we see images nowadays online they're not full high level resolution, you know the ones that you actually take with your camera. They're kind of optimized and much smaller for the web or for viewing in different apps.

Now there's a lot of difference between engineering and marketing when it comes to this. We, so far, have been talking about engineering terms but marketing will sometimes fudge these numbers. For instance they'll use for kilobit 1000 instead of 1024. They'll round up a lot. Very often they'll do things like say you have a 100 megabit connection but that's only downloading things. Uploading things sometimes you're a lot smaller. They kind of get away with this with marketing. An engineer wouldn't say that. An engineer would specify up and down speeds but marketing will just kind of give you the larger one.

Of course marketing also uses speeds up too. So you may have promised to you 100 megabits per second but, in fact, that's just the maximum you can get and very often you're at a fraction of that depending upon use in your neighborhood and conditions and things like that.

Also net neutrality comes into this a little bit because sometimes you deal with issues like you may find that videos stream really great from services like Netflix and Hulu and such that pay a little extra to have their streams go really fast but then from other sites or when transferring files yourself you may find it's a lot slower. Sometimes networks will actually put things in faster lanes and slower lanes.

Now people often confuse bandwidth with other things. One thing, for instance, is throughput. Throughput is kind of like average speed. So your average speed might be your throughput but your actual speed, your bandwidth, is what you have right now. So your bandwidth right now may be slower than normal but your throughput is just basically your average.

The biggest confusion is when people say bandwidth what they mean is data transfer. So, for instance, you'll say I'm out of bandwidth with my mobile plan or I've reached my bandwidth limit or something like that. That's actually incorrect. That's actually talking about the amount of data transfer. It's like saying distance. You might have enough fuel in your car to go 300 miles but you wouldn't say that's the limit on your speed. You would say that's the limit on your distance just as these limits are limits on your data transfer. Not limits on your bandwidth.

So don't use the term bandwidth when actually talking about data limits.