Testing upload/download bandwidth speeds for verification

[Rick Stevens]

Suvayu Ali wrote:
> Hi Daniel,
> 
> Daniel B. Thurman wrote:
>> Of the several sites I have tried, they all more or less
>> seemed to be in close agreement with one another in
>> terms of the bandwidth speeds, i.e. my connection
>> speed is quoted at 768KB/s up and 3MB/s down,
>> and the farther away from central, the more reduced
>> is the speeds are.
>>
>> The average speed tools says that I have measured
>> speeds of 720-30 KB/s up and 2.0-5MB/s down.
>>
>> Why is it however, that when downloading software
>> from the various Linux/M$ and other downloads sites
>> I am seeing on average, speeds of 200-320(max) KB/s
>> and never see anything much faster than that?
>>
>> Is this normal?
>>
> 
> Pardon me if this seems rather dumb or has been addressed by another 
> post in the thread (I haven't gone through the whole thread), but are 
> the speeds for your ISP KBps/MBps or Kbps/Mbps? Note the 
> capitalized/small `B's.
> 
> If the speeds are in Kbps/Mbps, then what you get is normal. KBps/MBps 
> would be Kilobytes/Megabytes whereas Kb/Mb would be Kilobits/Megabits. 
> It is common practice to quote bandwidth speeds in bits rather than 
> bytes. To convert between the two just divide by 8,
> i.e. 2Mbps / 8 = 256KBps

To clarify, a capital "B" is used to indicate bytes per seconds (Bps), a
lower case "b" to indicate bits per second (bps).  bps was also known
"back in the day" as the "baud rate" (although that's not completely
accurate).

(wistful)  I remember my 300 baud (300bps) acoustic coupler modem.....
:-p

On a more serious note, some sites limit download bandwidth on each
connection made so the sites can handle more connections.  Example, if a
site has a 2Mbps connection and one person starts a download, that
person could suck the entire 2Mbps pipe, thereby blocking others from
downloading.  If the site puts in a 256Kbps limit on each connection,
they can handle eight simultaneous connections.  kernel.org does this,
for instance (I think they limit to 128Kbps).

Some sites also vary the limit.  They start out with a large limit, but
narrow it down the longer the download takes.  The idea is that if you
need a download of something small, you get it fast.  If you're
downloading a bunch of stuff, they keep squeezing down until you hit the
minimum they allow and the remainder of the download continues at that
limited rate.

These are some of the reasons things like BitTorrent were created.
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- Rick Stevens, Systems Engineer                      ricks at nerd.com -
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