...
Below
...
is
...
a
...
perl
...
sub
...
you
...
could
...
embed
...
in
...
a
...
perl
...
script.
...
It
...
assumes
...
you
...
have
...
a
...
min
...
RTT
...
and
...
the
...
lat
...
longs
...
of
...
source
...
and
...
destination.
...
You
...
could
...
also
...
extract
...
the
...
code
...
to
...
calculate
...
the
...
distance.
...
Alternatively
...
if
...
you
...
have
...
the
...
lat
...
longs
...
in
...
spreadsheet
...
columns
...
then
...
you
...
could
...
write
...
a
...
function
...
(see
...
the
...
attached
...
spread
...
sheet).
| Code Block |
|---|
################################################################################
# Calculate alpha given the lat longs of the source (monitor) and target (remote)
# hosts, together with the minimum measured RTT in msec between them.
# alpha=distance_between_monitor_and_remote(in kms)/(100*min_RTT(in msec)).
# South latitudes are negative, east longitudes are positive. They are in
# decimal degrees. 57.2958=180/pi coverts degrees to rdaians.
# True radius varies from 6357km (polar) to 6378km (equatorial).
# See http://www.planet-source-code.com/vb/scripts/ShowCode.asp?txtCodeId=670&lngWId=6
# If it is not possible to calculate alpha due to an invalid RTT (e.g. no digits,
# just a period (.), then getalpha returns a period.
# Example:
# getalpha($src-latlong, $tgt_latlong, $min_rtt)
# getalpha('31.77 35.23', '9.98 -84.07', 121.223) sub getalpha {
my @monitor_latlon = split(' ', $_[0]);
my @remote_latlon = split(' ', $_[1]);
for (my$i=0;$i<2;$i++) {
unless(($remote_latlon[$i]=~/^-{0,1}\d*\.{0,1}\d+$/)
&& ($monitor_latlon[$i]=~/^-{0,1}\d*\.{0,1}\d+/)) {
return ".";
}
}
my $min_rtt = $_[2];
my $alpha;
my $min_dis=100000; #Initialise to an impossibly large value >> circumference of earth.
if (defined($min_rtt) && ($min_rtt=~/\d/) && ($min_rtt>0)) {#Is there a valid $min_rtt
my $distance=((6378.7)*(acos((sin($monitor_latlon[0]/57.2958))
*(sin($remote_latlon[0]/57.2958))+(cos($monitor_latlon[0]/57.2958))
*(cos($remote_latlon[0]/57.2958))
*(cos(($remote_latlon[1]/57.2958)-($monitor_latlon[1]/57.2958))))));
if($distance>$min_dis) {$distance=$min_dis;}
$alpha=$distance/(100*$min_rtt);
}
else {$alpha=".";}
return $alpha;
}
|