[wellylug] [OT] Internet & Citylink

[Jamie Dobbs]

David Antliff wrote:

> On Mon, 28 Feb 2005, Cliff Pratt wrote:
>
>> The rule of thumb used to be to divide by 10. That was to allow for 
>> the overhead of stop and start bits. I guess that only applies to 
>> serial port lines. I also guess that it doesn't apply to ADSL, but 
>> I'm not sure why. Anyone care to comment?
>
>
> Because on broadband services the overhead is transparent to the user? 
> The advertised speed is customer payload rate, not connection speed or 
> symbol rate or anything like that. So a 256kbps link is 256 * 1000 (a 
> kilobit is 1000 bits, not 1024) which is 256000/8 = 32000 Bps or 
> 31.25KB/sec.
>
1000 bits is NOT a kilobit (or at least wasn't when I went to either 
University or Polytech, or in the 25 years I've been using computers).
The numeric base of computers is powers of 2, and you cannot get 1000 
from a whole power of 2, the closest you can get is 1024 which is the 
correct definition of kilo in computer terms.

So to correct your calculation 256kbps = 256*1024 = 262144/8 = 32768 Bps 
= 32KB/sec (which just happens to be the download rate I saw many times 
when on a 256kbps connection)





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