How do I detect the network speed of a visitor?

How do I detect the connection speed of a user that is visiting my page. Baiscally I want to know if they are dial-up, or high-speed of some sort. I need this for an analytics packaage I am writing.

Worth 500 points.

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I've found a solution which is simple, but gives usable connection speed info. Put lines following lines into php:

function microtime_diff($a, $b) {
list($a_dec, $a_sec) = explode(" ", $a);
list($b_dec, $b_sec) = explode(" ", $b);
return $b_sec - $a_sec + $b_dec - $a_dec;

function test_speed($test_size) {
$start_time = microtime();
$comment = "<!--O-->";
$len = strlen($comment);
for($i = 0; $i < $test_size; $i += $len) {
echo $comment;
$duration = microtime_diff($start_time, microtime());
if($duration != 0) {
return $test_size / $duration / 1024;
else {
return log(0);

$speed = test_speed(1024);
if($speed > 50) { // a fast connection, send more byte for more accuracy
$speed = test_speed(10240);
if($speed > 500) { // a really fast connection, send even more byte for
more accuracy
$speed = test_speed(102400);
echo sprintf("Download speed is %0.3f kb/s", $speed);
You cant get that info directly.  Best you could do is create a bandwidth test, by maybe having them upload a file, and determining the time it took to upload X bytes.  But there is no #users_connection_speed# type variable.
richardsimnettAuthor Commented:
I have found that the solution is to purchase an aggregate database containing ip ranges, and associated net speeds. Its simply a matter of having this table in a database, and querying the incoming IP against it. It has proven to be about 90% accurate so far.

Spiffy, what database did you end up going with?  The ones I saw seemed pretty darn pricey :(
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