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i'm from Malaysia. I am subscribed to 2mbps pack from my country's ISP. But all i get is only 200kbps when download files from the internet, when i test my speed on speedtest.com , it shows me 1.7mbps.

I am pretty confused , ISP should give users what they stated , yeah a 2mbps. But i only recieved 200kbps and the speedtest shows 1.7mbps which makes me confused even further.

So i started googling and found out that it is related to something called VPN compression?

can anyone explain to me how these things works? why am i getting much much lower speed than i have subscribe to. (I am using a D-Link DSL-2750 U modem)


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Add links to your speedtest and run the glasnost test on your connection –  Akash May 10 '12 at 7:40
broadband.mpi-sws.org/transparency/glasnost.php : select the HTTP transfer option and run the test. Also, speedtest shows 1.7 mbps or kbps? (4th line of your question says kbps). Additionally, is your download speed 200k b ps, or 200k B ps? –  Akash May 10 '12 at 7:43
There's a little confusion here. Your title says your speed tested at 1.7mbps, while your question body says 1.7kbps. Which is it? Also, keep in mind speed is limited by the slower of the two sides of the connection. You could be on 100mbps fibre and still suffer painfully slow downloads if the server bandwidth is limited. –  Bob May 10 '12 at 7:43
b = bits , B = bytes –  Akash May 10 '12 at 7:56
@Akash You should probably post that as an answer. And Edward, you should accept the answer if/when he posts it if it helped you resolve your problem. –  Bob May 10 '12 at 8:51

7 Answers 7

Mb/s means megabits per second. To convert to megabytes (MB), you simply divide by 8, since there are 8 bits in a byte:

2Mb/s = 2Mb/s * 1Mb/8MB = 0.25MB/s = 250 kB/s

So you can theoretically cap out at just under 250 kilobytes per second.

Note that I have used megabyte here, which assumes 1000 kilobytes per megabyte. The convention for unit steps of 1024 is used for mebibyte (MiB), which consists of 1024 kibibytes (kiB). What your browser/download tool uses depends on how the developers implemented the math, but in the case they do use mebibytes/kibibytes, your theoretical maximum speed would simply be:

2Mb/s = 2Mb/s * 1Mb/8MiB = 0.25MiB/s -> 0.25MiB/s * 1024 kiB/MiB = 256 kiB/s

Note that kilobyte is a common misnomer for kibibyte, but the difference is neglegible for most purposes (as you can see above, both results are fairly close to eachother). If you require an exact calculation, and you're unclear what units the result is in, you need to ask the developers how the math was implemented in the program or operating system.

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Your speedtest shows 1.7Mbps, your connection is 2mbps, your download speed is approx 200kBps.

Nothing is wrong



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Actually the internet service providers mentioning our internet speed in bits per second.

And your speedtest website also showed it to you in bits per second ,whatch it clearly.

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But in our computer level,our download managers or some applications shows the download speed in Bytes per second like this,

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8 bits = 1 Byte

So if your ISP mentions 512 Kbps , 1 Mbps , 2 Mbps , 4 Mbps ., to calculate your download speed in Bytes simply divide it by 8 , that will be your download speed in KiloBytes or MegaBytes . example

512 Kbps = 64 KB/s

1 Mbps = 1024 Kbps = 128 KB/s

2 Mbps = 2048 Kbps = 256 KB/s

4 Mbps = 4096 Kbps = 512 KB/s

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SI prefixes (e.g. kilo, mega) are not capitalized, only the abbreviated forms (e.g. k, M) are. –  Breakthrough May 10 '12 at 17:39

Line speeds are measured in decimal units and in bits per second. Data transfer rates are measured in binary units and bytes per second. Also, the line doesn't just carry data, it has to carry address and control information as well. The overhead of the line encoding is already figured in, but the overhead of control and address information is not.

So if you have a "2Mbps DSL" service, that means your line carries 2,000,000 bits per second. You divide by 8 to get bytes per second, or 250,000. You can then divide by 1,024 to get kilobytes per second, or 244KB/s. TCP over DSL has a maximum efficiency of about 95%, so multiply by 0.95 to get 232KB/s. So a 2Mbps DSL line would be expected to provide a maximum download speed of 232KB/s.

So you're in the ballpark.

By the way, speed testing sites generally just measure the usable data rate over TCP and then multiply by eight. So a 2Mbps DSL line, even if it was actually providing precisely that line rate, would actually give a lower measurement (around 1.85Mbps).

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Never heard about 95% efficiency thing. –  Boris_yo Jun 3 '12 at 5:07
@Boris_yo: It's the difference between how much data the line can carry and how much useful data TCP can carry over the line. Each packet contains address and control information as well as data. The address and control information uses up some of the line's capacity. –  David Schwartz Jun 3 '12 at 5:35

For various reasons, actual "speedtest" results are generally about 20% lower than provisioned speeds. This is just the way it goes. So with a 2mbps service, I would expect speedtest to show 1.8mbps. If I had 1.7mbps I would not complain.

The 200kbps is possibly due to restrictions on the server you are downloading from (most servers have outbound bandwidth restrictions to avoid being clobbered by DOS attacks) and possibly a problem with your TCP windowing. Since you are getting 1.7mbps from speediest, it is not likely to be a problem with your ISP.

More likely is that you have confused bps with Bps, as 200kBps = 1.6mbps

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Megabits and MegaBytes are very different too –  Simon Sheehan May 10 '12 at 11:01

Another possibility: your provider promised you DSL up to 2000 M where the dsl and 2000 M are in 36 font and the up to is in 2.5 font. You must share the bandwidth with people on the same physical wire. This is similar to UMTS where you share the bandwidth with others on the same cell.

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AFAIK DSL is not shared –  Akash May 10 '12 at 17:36
DSL itself is not shared, but your and your neighbor's line are connected to a DSLAM, and all of these DSL must share the DSLAM bandwidth. See en.wikipedia.org/wiki/Digital_Subscriber_Line#Typical_setup and en.wikipedia.org/wiki/… –  ott-- May 11 '12 at 9:24

People tend to forget to read the fine print. Most ISP don't say 2mbps, 20mbps, 200mbps. Or they do say it, but then in the fine print there's this:

They say UP-TO 2mbps. Unless they made any guarantee it could very well be only 0.5mbps and you're SOL then.

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