[CentOS] Ping time resolution

Mitja Mihelič mitja.mihelic at arnes.si
Mon Oct 18 03:17:03 EDT 2010


Hi!

We have encountered a rather weird problem on a machine that we use for 
our network latency check (smokeping with fping).
For an hour (or so) after boot it reports the ping time with a 
microsecond accuracy (ad it should).
Then the millisecond accuracy starts.
We have yet to identify the cause and the logs currently do not show 
anything.
Please find an example of a good and a bad result below.

Regards,
Mitja

When it works: (microsecond accuracy):
[root at server ~]# ping test.example.net
PING test.example.net (123.1.2.3) 56(84) bytes of data.
64 bytes from test.example.net (123.1.2.3): icmp_seq=1 ttl=62 time=0.562 ms
64 bytes from test.example.net (123.1.2.3): icmp_seq=2 ttl=62 time=0.452 ms
64 bytes from test.example.net (123.1.2.3): icmp_seq=3 ttl=62 time=0.579 ms

--- test.example.net ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 1998ms
rtt min/avg/max/mdev = 0.452/0.531/0.579/0.056 ms


And when it does not (millisecond accuracy):
[root at server ~]# ping test.example.net
PING test.example.net (123.1.2.3) 56(84) bytes of data.
64 bytes from test.example.net (123.1.2.3): icmp_seq=1 ttl=62 time=1.99 ms
64 bytes from test.example.net (123.1.2.3): icmp_seq=2 ttl=62 time=0.999 ms
64 bytes from test.example.net (123.1.2.3): icmp_seq=3 ttl=62 time=0.000 ms
64 bytes from test.example.net (123.1.2.3): icmp_seq=4 ttl=62 time=0.000 ms
64 bytes from test.example.net (123.1.2.3): icmp_seq=5 ttl=62 time=0.000 ms

--- test.example.net ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 3999ms
rtt min/avg/max/mdev = 0.000/0.599/1.999/0.800 ms



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