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I subscribed in a 1Mbps broadband internet (data only). The provider said that customers would only get 60% of it which is approximately 600kbps of the 1Mbps, which is enough for me. But I've been observing my download speed and it is limited to only 12%, i can't get past 120kbps. Every time my DL speed exceeds 120kbps it suddenly drops down again. I think mine is filtered. Is there a way around this? My modem router is Prolink ADSL2+.

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    What does speedtest.net report your speed as?
    – MDMarra
    Oct 6, 2009 at 15:00
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    Are you sure that you're not hitting 120 kilobytes per second (kB/sec) (which is close enough to 1 megabit per second [mbps])? 1 kB/sec is the same as 8 kilobits per second (kbps)
    – Blixt
    Oct 6, 2009 at 15:01
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    Sounds like you are getting exactly what you are paying for. ;)
    – Troggy
    Oct 6, 2009 at 15:11
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    So you can't go past 12kb/second transfer rates on downloads?
    – EvilChookie
    Oct 6, 2009 at 15:15
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    This is an excellent resource question for SU because I know a lot of people get confused by this. Even programmers. ;)
    – Troggy
    Oct 6, 2009 at 15:26

6 Answers 6

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1Mbps = 1 Mega bit per second and 1 byte = 8 bits so 1 Mbps = 0.125 Mega byte per second.

Bit is typically represented by a lowercase b. While byte is typically represented by an uppercase B

So 8 Mbps = 1 MBps.

This is a classic marketing ploy since all the speeds look like they're 8x faster.

On the plus side, you're actually getting the full bandwidth you're paying for. I pay for a line that's up to 10 Mbps and only ever get about 8 Mbps.

Edit: If you understand the bit vs byte issue, then make sure the speed readings you're getting are correct. Running a speed test while no other internet activity is happening is the best way to get an accurate reading of your connection speed, applications often have an inaccurate speed reading.

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  • Simply put 1mbps is 1024 kbps, but the thing is i'm only getting 120kbps on download speed..and that's far..
    – Kaile
    Oct 6, 2009 at 15:15
  • @Kalie: Make sure to look at bytes vs bits. 1 mega bits per second = 1024 kilo bits per second. You are getting 120 kilo bytes per second down, which would be equal to about 1 mega bit per second.
    – Troggy
    Oct 6, 2009 at 15:17
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    1024kb/s is 128kB/s - so pretty much what you're getting.
    – Phoshi
    Oct 6, 2009 at 15:17
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    Well thing is, 1MB/s = 1024KB/s, just like 1mbps = 1024kbps, the problem is when you mix the two: 1mbps = 125KB/s, 1MB/s = 8192kbps
    – Blixt
    Oct 6, 2009 at 15:18
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    There was actually a good reason for this. 1 byte = 8 bits hasn't always been the norm. Byte size is determined by the computer architecture and while most computers have standardized to 8 bits this wasn't the case at the dawn of digital telecom. Depending on the system a byte could be anywhere from 4-36 bits. The only reliable way to measure speed between different systems was to measure in bits.
    – Kenneth Cochran
    Oct 6, 2009 at 15:31
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Are you sure that you're not hitting 120 kilobytes per second (kB/sec) (which is close enough to 1 megabit per second [mbps])? 1 kB/sec is the same as 8 kilobits per second (kbps)

See Wikipedia for more explanation on data rate units.

To bring an end to all the speculation going on here... what does http://www.speedtest.net/ tell you?

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  • I fully understand the ranges of kilobytes coz i'm a programmer...and trust me 120kbps is far from 1mbps..especially when talking about download speed... i'm wondering if someone knows if my modem is filtered or whatsoever..coz 120kbps is really slow for me.
    – Kaile
    Oct 6, 2009 at 15:09
  • Well I was just thinking since just about any download application/web browser will show your speed as kilobytes per second. So if an application shows you that it's downloading at 120 kb/sec it might very well mean 120 kilobytes per second. In any case, I doubt your modem is the limiting factor since ADSL2+ is capable of supporting download speeds of at least 24 megabits per second.
    – Blixt
    Oct 6, 2009 at 15:12
  • Kaile, on a 1 Mbit/sec internet connection, the maximum download speed is 125 kbytes/second (in theory), so 120 kbps under real-world conditions is by no means far off but a very good result indeed. the connection speed is always measured in BITS/second while a web browser usually reports the download speed in BYTES/second (8 bits in 1 byte)
    – Molly7244
    Oct 6, 2009 at 15:18
  • Hmmm..maybe I should really ask the provider now... I was just observing if my download speed is really limited (and it is, in fixed value). I'm also using torrent applications in which my download speed should reach its full potential..but it's still limited to 120kbps and down.
    – Kaile
    Oct 6, 2009 at 15:19
  • torrent applications usually report kilobytes per second not kilobits. I think blixt hit your problem on the head
    – JamesRyan
    Oct 6, 2009 at 15:21
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Actually, there are three things going on. One is the bits versus bytes issue that others have mentioned. Another is that line speeds are reported in decimal units, not binary units. And a third is that the line has to carry not just data but also address and control information.

A 1Mbps line carries 1,000,000 bits per second, or 125,000 bytes per second. Address and control information takes about 4% of the bandwidth, leaving about 120,000 bytes per second for data. A kilobyte of data is 1,024 bytes, so that means you would expect 117KB/s.

So you're dead on.

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Some ISPs do take measures to cap bandwidth. Some have even covertly resorted to traffic shaping (limited speed based on the type of data). Whether they have the right to is debatable (see net neutrality).

Comcast was recently caught doing this with bitorrent data.

You can try to test this by downloading from various sources one at a time using different protocols and see if there are discrepancies. Keep in mind your speed is limited by the capacity of your download source as well. An overloaded website is going to be a slow download no matter what you try to do on your end.

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To try to simplify the other answers, providers report in Bits because they give higher numbers. Most applications report in bytes.

1mbps connection = 128KB/s. When downloading in Firefox, Steam, uTorrent, etc. the highest speed you will ever see is 128KB/s.

To reinforce what is happening, the difference between bytes and bits is 1/8, or 12.5%. This is surely what you're seeing.

As far as seeing the actual cap, your bandwidth is limited to the advertised 1mbps by the company, and you can often see the bandwidth jump initially beyond the limit before the ISP caps the speed. As an example, I have a 10mbps connection, but our ISP offers a 20mbps package. While my speed is usually maxed out at 1.25MB/s, I can initially see the speed jump up to 2MB/s before slowing down to the speed I'm paying for.

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    No, providers state the bandwidth in bits even when they're selling it to technical people who need wholesale bandwidth in the thousands of megabits per second. The reason for this is that it's the standard. Ethernet speeds come in 1 gigabit, 100 megabit, and 10 megabits per second, just as an example. You can't get Ethernet hardware that will give you 14.5 Megabits per second. Or 39 Megabits per second. Wireless speeds are a bit of an anomaly in this regard, but they come in standard speeds as well.
    – Ernie Dunbar
    Oct 6, 2009 at 17:35
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    Line speeds are reported in decimal units, not binary. A 1Mbps line is 1,000,000 bits per second.
    – David Schwartz
    Oct 4, 2011 at 17:30
  • 1mbps doesn't actually make sense, because it would be 1 millibit per second. See, spelling is effing important! M is mega, m is milli. Simple, really.
    – Jürgen A. Erhard
    Jul 4, 2014 at 8:41
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I think your question is about file transfer rate, not differences in in connection rates. It is not about bits or bytes or 1024.

Your file transfer rate will not be synchronous with your connection rate, it will be about 1/8th of the connection rate. that is a MAX rate, so add to that the normal lag of the internet and you get total slowdown. This is an internet fact.

A fact, that those of use using FTP have to deal with. I have attampted to research the issue, but there is not alot of information out there, since not alot of people do FTP, some who do don't realize they are (Google Docs), most FTP activity is small files, and for large files you can just stream the content.

Generally, this is not a problem for DL, since we all have 10M or better home connections, so you can DL at about 1M.

Where this really sucks is on Upload. Home internet connections have an upload rate of less then 1M, usually 768K or 512K. 1/8th of that sucks, about 100k is what i get on a good day, average is around 35k.

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