[OT, embarrassing] trouble understanding ping output
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
I have a script pinging my ISP (details below) and I don't understand
the results. Some output:
> 2391 Thu Feb 26 01:14:39 2009 -- 5 packets, time 45ms == max rtt: 351.654 ms
> 2392 Thu Feb 26 01:14:45 2009 -- 5 packets, time 46ms == max rtt: 344.855 ms
> 2393 Thu Feb 26 01:14:50 2009 -- 5 packets, time 46ms == max rtt: 340.359 ms
> 2394 Thu Feb 26 01:14:55 2009 -- 5 packets, time 47ms == max rtt: 345.226 ms
> 2395 Thu Feb 26 01:15:01 2009 -- 5 packets, time 46ms == max rtt: 356.115 ms
> 2396 Thu Feb 26 01:15:06 2009 -- 5 packets, time 47ms == max rtt: 350.294 ms
> 2397 Thu Feb 26 01:15:12 2009 -- 5 packets, time 57ms == max rtt: 341.351 ms
> 2398 Thu Feb 26 01:15:17 2009 -- 5 packets, time 58ms == max rtt: 350.854 ms
What I don't understand is how the maximum round trip time can be 350 ms
when it takes only 50 ms for the test. Can anyone explain this?
Details:
This is a perl script running on the server on my LAN. It does a 5
packet, 100 byte, ping flood (attempting to duplicate the Cisco router)
every 5 seconds. The output is collected and munged, and displayed with
the loop counter and a timestamp.
I'm doing this because a couple times a day, nagios (a new installation
on this same host) has been telling me the rtt to the ISP's border
router (T1, half a mile) has been high. The vast majority of the time,
the max rtt is 5 ms.
The host is *very* lightly loaded (both cores 95%+ idle). It runs lenny
from a software RAID1 on 2 SATA disks, no X.
There's another script, running at the same time on the same host, that
telnets into the router and pings from there. It's never reported a rtt
higher than 25 ms -- I'm assuming that means I've got a problem
somewhere, not the ISP / phone company.
My first problem is deciding what my problem is...
- --
Glenn English
ghe@slsware.com
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.8 (Darwin)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org
iEYEARECAAYFAkmmsdMACgkQ04yQfZbbTLanEQCeNuXty6u2b27upSRWkCwfv7OI
sWkAnRMwuKL59Yi64MnaKY42qq1hLxXi
=BsC3
-----END PGP SIGNATURE-----
Reply to: