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On Friday 25 July 2003 12:16 pm, Paul Larue sent the following:

> Hi Elan,
> You could do a simple estimate based on 'file size' / 'connection
> speed'. Thus, for a file of 1024 bytes (1Kb) you'll do something like
> 1024/42 if the connection is of 56Kbps. I used 42 since 56k is the
> downloading speed and uploading speed is approximately 75% of that.

Not to be pedantic, but 56kbps is the max download speed - you'll very rarely 
see an actual 56kbps, it's normally around 40-50kbps.  Upload speed is 
generally still 33.6kbps.  Also, 56kbps is 56 kilo-BITS per second, whereas 
1Kb is 1024 BYTES.  

You can assume 8 bits to a byte, so, ignoring overhead from any parity bits 
and ignoring the overhead of TCP/IP packet headers etc, you could assume 
that, if the user's upload speed is 33.6kbps / 8 = 4.2Kb/s data transfer 
rate.  

In reality, it's hard to get an estimate that's anywhere near accurate since 
it'll depend on what else is using their connection (do they have any other 
downloads/uploads running), the speed of their machine, quality of their 
phone line, etc etc etc.


> However, this would imply that you know the speed of the connection.
> Either the user enters it somewhere or you call some obscure Win32API
> that would return the connection type selected by the user in "Internet
> Options". Check the API Text Viewer or MSDN for more info.

No, no!  Try to avoid proprietary Windoze API stuff like that - it's only ever 
going to work on Windows, using IE, and even then probably won't work if the 
user has their security settings set right.


> A better test (and more reliable) would be to upload a small text file
> of 1kb to the target server as test and then deduce the upload speed.
> You could show that phase to the user as "calculating upload speed" for
> example.

Even then, you need a pretty big file to get a reliable average transfer rate.


Whatever you do needs to be server-side.  The browser should supply a 
Content-Length that you can use to see how big the file is, but I don't 
*think* that a PHP/ASP script runs until the file is fully uploaded and saved 
to a temporary directory.  I could be wrong on that bit.


Anyway, good luck with it!


Cheers


David P
http://www.preshweb.co.uk/


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