Re: [tlug] Latency thru firewall

[Josh Glover <jmglov@example.com>]

Quoth Mike Gauthier (Thu 2002-09-19 08:34:50PM +0900):
> On Wed, 18 Sep 2002, Sven Simon wrote:
> 
> > The firewall I'm sitting behind doesn't let ICMP traffic thru and I
> > only have the ssh port open, so ping obviously times out. Is there
> > another way to determine the latency to the machine I connect to
> > via ssh other than using ping?
> 
> Try this command.
> 
> time nmap -n -sT -p 22 -P0 <ip address to "ping">

Great suggestion. You could add a little Perl to give you a quick average
latency:

i=0
while [ $i -lt 100 ]; do
	/usr/bin/time -a -o /tmp/latency.data nmap -n -p 22 -P0 -sT ip_addr >/dev/null
	let i+=1
done
cat /tmp/latency.data | perl -e \
'my $tot = 0;
my $num = 100;
while( <> )
{
	if( $_ =~ /\s+(\d+\.\d+)\suser/ )
	{
		$tot+=$1;
	}
}
print "Ave: ". $tot/$num."s\n";'


Obviously, you can change the number of iterations by changing the '-lt 100' to
'-lt num' and changing the 'my $num = 100' to 'my $num = num', where num is the
number of iterations desired.

Also remember that since this is a TCP connect() scan, it is going to show up
in the logs of the remote host. If you do not own said machine, you may want to
notify the administrator of it that you are doing some latency scanning.


-- 
Josh Glover <jmglov@example.com>

Associate Systems Administrator
INCOGEN, Inc.
http://www.incogen.com/

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