King of the Potato People

Code, photos and ramblings of Rick Hodger

Measuring bandwidth

without comments

An issue that comes up for me at work time and time again is customers misunderstanding how bandwidth is measured.

Data is traditionally measured in Bytes. A CD contains 650MBytes of data. Bandwidth is measured in bits however, and this is what most customers misunderstand. A CD measured in terms of bandwidth, is 5,200Mbits (there are 8 bits per byte). Note that in writing, you use a capital ‘B’ to denote Bytes, and a lower-case ‘b’ to denote bits.

The issue is that bandwidth is traditionally measured in bits, not bytes. A 1Mbit circuit lets you download at 100KBytes/second. A lot of people make the mistake of thinking that a 1Mbit circuit is the same as downloading at 1MBytes/second.

This becomes a problem when a customer - as has happened today - complains of a slow speed problem. The systems (which I built and maintain) show this customer as downloading up to 32Gbits per day. They dispute this via the phone, proclaiming that they only downloaded “4 gig” (in a 5 hour window, I’ll add). If you do the math: 4*8 = 32. 32Gbits. On a standard ADSL line, that’s a crazy amount of usage - averaging around 1.8Mbit/s for that 5 hour window. During peak hours, an ADSL Max line (due to contention) may only be able to achieve 2Mb/s. It’s a classic case of someone mistaking Bytes for bits… of course, explaining that to them is another matter.

Written by rick

April 24th, 2008 at 6:04 pm

Posted in Geek

Tagged with , , , , , ,

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