Your ISP advertises a 40Mb connection, but that doesn’t look anything like the download speed you see when you’re grabbing a big file. What’s the deal? Are you not getting all the bandwidth you’re paying for?
Dear How-To Geek,
The package deal I have through my local ISP is for a 40Mb connection (that’s the wording they use). When I download files I get around 4.5-5 (and definitely not 40!) Now… this doesn’t seem to be a big deal, because I can download everything I want pretty quickly, YouTube doesn’t stutter or anything, I never have to wait to load my email or web page, etc. But if I’m paying for a 40Mb connection why am I not getting a 40Mb connection?
This is a fun question because it allows us to discuss and clear up a common misconception, and learn a little bit about computer history along the way.
Let’s start by delving back into the history of computer networks. Data transfer over networks has always been measured in bits. A bit is the smallest and most basic unit of measurement in computing and digital communications. Bits are most commonly represented in the binary system, via 0 and 1. Bit, in fact, is a contraction of the the longer phrase “Binary Digit”.
The speed of a network is denoted using a bit-per-second notation written bits/second and almost always shortened to b/s. Originally, networks were so slow that their speed was measured in just bits. Then, the network speeds increased and we started using the prefix kilo to denote thousands of bits. Nearly everyone throughout the 1990s connected to their ISPs using 56k modems (or, 56 Kb/s). Then, with the advent and adoption of broadband technology like DSL and cable modems, speeds increased again and we started talking about speeds in terms of not just bits or kilobits, but megabits, and consumers started seeing connection speeds framed in terms of MB/s.
Now, here’s where things get confusing for the average non-geeky-Joe. Computer storage is not measured in bits, it’s measured in bytes. A bit, as we’ve established, is the tiniest unit of measurement in the digital kingdom, that primordial 1 or 0. A byte, however, is a unit of digital information that (in nearly every computer system and most certainly in the Windows, Linux, or OS X system you’re using) is eight bits long. Another term, used by computer scientists to avoid confusion over the different size byte structures out there in the world, is octet. In other words, the byte system that your operating system uses is a bunch of bits strung together in groups of eight.
This difference is where, on the surface, it all seems to fall apart. You see, you have a broadband connection that is capable of 40 megabits per second (under ideal conditions, 40,000,000 bits come down the line). However, as we just learned, a byte is 8 bits. Your operating system and all the apps on it (web browsers, download helpers, torrent clients, etc.) all measure data transmission and volume in bytes not bits. If we divide the speed of your connection (measured in bits) by 8, we arrive at something resembling the download speed you’re seeing in your speed tests: 40,000,000 bits becomes 5,000,000 bytes. Divide those values by a million to get us back to a more comfortable mega denotation and they become 40 megabits and 5 megabytes, respectively. Slap on the per-second label to indicate we’re talking about data transmission speeds and suddenly we have the speed your ISP is advertising (40 Mb/s) and the speed you’re seeing when you max your connection (5 MB/s).
Although it’s certainly confusing to consumers, you are in fact getting exactly what you’re paying for (and can even pat yourself on the back because you’re getting downloads speeds consistently at the edge of what your internet package supports).
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