Converting from bandwidth to traffic gives different results depending on operators position?

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+1 Q:

Converting from bandwidth to traffic gives different results depending on operators position?

Hi.

This must be a stupid question, but nevertheless I find it curious:

Say I have a steady download of 128Kbps.

How much disk space is going to be consumed after a hour in Megabytes?

128 x 60 x 60 / 8 / 1024 = 56.25 MB

But

128 x 60 x 60 / 1000 /8 = 57.6 MB

So what is the correct way to calculate this?

Thanks!

+4 A:

In one calculation you're dividing by 1000, but in another you're dividing by 1024. There shouldn't be any surprise you get different numbers.

Officially, the International Electrotechnical Commission standards body has tried to push "kibibyte" as an alternative to "kilobyte" when you're talking about the 1024-based version. But if you use it, people will laugh at you.

Paul Tomblin 2009-05-06 16:53:43

I actually quite understand this! :)Point is, that in first case I convert to bytes from bits, then to kilobytes, and in other case, I convert to kilobits, and then to kilobytes.So, which approach is the stadnard accepted one?

SyRenity 2009-05-13 21:23:51

No, in the first case you divide by (8*1024) and in the second you divide by (8*1000). They're different numbers. Generally in computer science, people use 1024, except drive manufacturers who use 1000.

Paul Tomblin 2009-05-14 01:06:06

Actually, I just wanted to know what is the correct order :) - but now it makes sense to always start from bits to bytes conversion (see my answer).

SyRenity 2009-05-19 07:42:56

Division is commutative - it doesn't matter what order you do the operations in, you'll always get the same answer.

Paul Tomblin 2009-05-19 11:33:23

+2 A:

Please remember that there is overhead in any transmission. There can be "dropped" packets etc. Also there is generally some upstream traffic as your PC acknoledges receipt of packets. Finally since packets can be received out of order, the packets themselves contain "extra" data to all the receiver to reconstruct the data in the proper order.

JonnyBoats 2009-05-06 17:07:15

Thanks, I actually spoke about the ideal environment.

SyRenity 2009-05-13 21:24:37

Ok, I found out an official explanation from Symantec on the matter: http://seer.entsupport.symantec.com/docs/274171.htm

It seems the idea is to convert from bits to bytes as early as possible in calculation, and then the usual 1024 division comes in place.

I just hope it's a standard procedure, and not Symantec imposed one :).

SyRenity 2009-05-19 07:40:57

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Converting from bandwidth to traffic gives different results depending on operators position?

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