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Summary: Bandwidth is a term you hear frequently but it can be confusing and it's easy to gloss over exactly what it means.
That's fast. Compared to me, anyway, that's fast. Given your ISP (from your email address) and the speeds you're seeing I'd guess you probably have cable internet. I'm going to bring out the oldest metaphor I have to try and put a handle on how fast is fast. No math, but first just a teeny, tiny bit of computerese. That part's inevitable. • First, let's define the term: bandwidth simply is the speed at which data is transferred. Sometimes bandwidth is also used to refer to the maximum capacity, or the fastest, that a connection could move data. Now let's define what you were told: 17237 kbps is 17237 "kilo-bits per second". "Kilo" is 1000, so what you're seeing is 17,237,000 bits per second. Your math is correct: mbps is "mega-bits per second" so that's17.237 million bits per second. For that to have some meaning, we need to understand what bits are, and how they're used to carry information. You probably know that a bit is a single "thing" that can be either 0 or 1. Nothing more, nothing less. Everything in your computer, everything digital, everything you communicate on the network and on the internet is built on the fundamental concept of a bit. Everything. The bit is the very definition of digital. "The bit is the very definition of
digital."
Bits are commonly handled in groups of 8 called bytes. If you look at 8 bits whose possible values are either 0 or 1 each, the collection can have up to 256 possible unique combinations: 00000000 Now, when we represent text - such as the text you're reading here - on a computer, the most common way to do so is to use one byte for each character. So if I type, "The quick brown fox jumped over the lazy dog," that took 44 bytes to store all the characters, including the spaces between the words. Now we break out the metaphor: The Bible. Let's be clear; it doesn't matter if you believe or not. This has nothing to do with the contents of the Bible, only its size. You've probably seen one, perhaps even own one, and have a good sense for how big it feels, how hefty it might be, and how long it might take to read it cover to cover. The Bible is a fairly sizeable common frame of reference. You can download the text of The Bible from project Gutenberg as plain text meaning that it has only the text of The Bible, in its simplest form. A representative copy in this digital form is about 5,000,000 bytes, or more commonly 5 megabytes. And here comes just a little math. Five megabytes at 8 bits per byte is, roughly, 40,000,000 bits. On your 17,237,000 bits-per- second connection, that means you can download the entire Bible in about two and a half seconds. In the other direction you're running 1,615 kbps, so it would take you about 25 seconds to upload it. Now let's compare that to some other common bandwidth figures and see how long it would take to transfer The Bible at those rates:
These are approximations meant to be examples of orders of magnitude. Your mileage will almost certainly vary and will likely be not quite as fast as the numbers above should you actually download a 5 -megabyte file. These numbers assume you have 100% of your connection available to you (which is not always true on shared resources like cable), and that the download is the only thing happening. I'm also completely ignoring any overhead caused by the way the internet and networking work in general. Typically, if you're getting within around 80-90% of these numbers, life is pretty good. Naturally, we don't all go around downloading Bibles all day. But using that as a common physical object that translates into an easy- to -remember number of bits (40 million), perhaps that'll help give a sense of what bandwidth might mean and how fast your connection might compare to others. As one final exercise for those so inclined, I'll point out that a data CD holds around 700,000,000 bytes, or 5.6 billion bits. A DVD? 4.7 gigabytes, or 37.6 billion bits. I'll let you do the math for your own connections, but for my T-1, that means with ideal conditions it would take me a little over an hour to download a CD and around 7 hours to download a complete DVD. Related:
• Recent Comments
Two items come to mind - First, speed tests are often poor examples of sustained download speeds. Comcast, for example, provides a much higher rate of throughput initially, then slows the download to the "rated" speed. This makes websites typically load quickly, but large files (like operating system patches) can take much longer. My cable modem is rated as 6 mbps, but will burst up to 18 mbps for typical speed tests. When I download large files, it slows back down to 6 mbps. - Second, many websites throttle how much throughput can be sucked up by a single connection. So, even though you may have the capability to download oodles of content very quickly, the website may restrict how quickly they will send it to you. Speed is nice, but sometimes not all it seems to be. Posted by: David Ball at June 10, 2008 12:52 PMI'm sure you've told us before but here goes.... Great articles and thank you. Posted by: Derek Miles at June 10, 2008 10:20 PMOften the high "burst" readings are inaccuracies in the way the timing is measured, because it is an average it relies on the last, lets, say, 15 seconds of transmission to show your speed. If you have only been downloading for lets say, 5 seconds, a speed calculated on the last 15 seconds is going to be erroneous - and depending on the exact calculation it may come out too high or too low. As to the bandwidth - its the number of communication channels available at any time. So a bandwidth of 10Mbps means that there is a "wide" enough pipe/cable to transmit signals that contain 10Mbits of data in a second. Also different technologies work differently - and different technologies are available in different countries. Whilst those speeds are typical for connections in the USA, in the UK the standard DSL connection is now 8Mbps (recently upgraded from 2Mbps). Some providers are rolling out ADSL2+ here which offers upto 24Mbps, though I'm not sure anyone actually gets that. Cable is available in the UK at speeds between 2Mbps and 10Mbps. Posted by: Eli Coten at June 11, 2008 05:37 AMThis is laughable. So many errors. -----BEGIN PGP SIGNED MESSAGE----- T-1 is 1.5 megaBITS, not bytes. Cable users can easily get All the costs depend on your ISP and location. So, I'm still not sure what all the errors you refer to are. Leo
iD8DBQFIUFgACMEe9B/8oqERAgzFAJ4nszDgXiIQkPTCb1jMTXQV8pBaVQCfZwcU -----BEGIN PGP SIGNED MESSAGE----- Derek: there are various speed testing sites around. My Leo
iD8DBQFIUFg3CMEe9B/8oqERAs3DAJ9qcRZNqIJOoKLwHNKVcZjTZKJrlwCfYOIW Nice article to explain this evolution in the meaning of bandwidth, although as others have noted, its use is a little confusing. Like many other technical terms, its meaning has moved beyond its original and precise interpretation. In this case the original meaning was the width of the freqency band which a channel or service can utilise. The natural consequence of the higher frequencies used in our data communications is that a channel can have a wider bandwidth but it is essentially the higher frequency that allows for data to be transmitted faster. Hence the consequence of the faster data rates has become synonymous with the term higher bandwidth. Ah well, it would be a most difficult language to use when explaining new technology if it were not allowed to evolve, however far it strays in meaning. And another pedanticism I highlight is that when talking about data rates, the convention is to use 'bits' not 'bytes' as the units. Hence the attempt by IT engineers to standardise on the lower case b to mean bits and the upper case B to mean bytes. I guess this is too subtle to survive in general use. And while we are talking about conventions, the prefixes Kilo and Mega when used in computer jargon, are not the same as the standard international prefixes of the same names. The international units (SI units) mean 1,000 (10^3) and 1,000,000 (10^6) but computerspeak has them meaning 1,024 and 1,048,576. Hence KBytes (or Kbits) has 1,024 bytes (or bits), and similarly for MBytes (or Mbits). These values are the result of the binary unit (bit) having two values, 0 or 1. Hence a byte (consisting of 8 bits) can have 2^8 = 256 distinct values; ie, the number of states (2) raised to the power of the number of bits (8). This 1,024 =2^10 and 1,048,576 =2^20 I am sure you are aware of these facts Leo and that you chose not to confuse people with the details. I guess I am a purist, and think it important that if people are wanting to learn about using computers, then they are intelligent and motivated enough to be told some of the basic facts. Please keep your enthusiasm for your site, it is excellent source of information. I used to use a Teletype(C) Machine a lot. Way back then Bandwidth was referred as BAUD or BAUD RATE. Switching terms now would be confusing for those who use the term Bandwidth. This article stayed in my mind and I just had to post a comment. Thanks Leo for being there for us. When I was teaching basic IT to telemarketers the best analogy I could come up with was the water system. The bigger the pipe you have coming into your house the quicker you'd fill your kettle etc. The original question was how does it compare so big numbers = more water = good :) Good article Posted by: Riff at June 12, 2008 04:25 PMI don't know if one of the comments covered this, but most downloading programs show KB/s (kilo-bytes per second) and most speed tests will show kbps (kilo-bits per second)... A byte is 8 bits, so to show your download speed, simply divide your speedtest's kbps by 8 to get KB/s... 17237 kbps = 2 MB/s Down so kbps to mbps, divide by a meg (1000-units) Post a comment on "What is bandwidth?":
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