Section: System Manager's Manual: iputils (8)
Updated: 14 March 2007
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clockdiff - measure clock difference between hosts
clockdiff [ -o] [ -o1] destination
clockdiff Measures clock difference between us and
destination with 1 msec resolution using ICMP TIMESTAMP
packets or, optionally, IP TIMESTAMP option
option added to ICMP ECHO.
Use IP TIMESTAMP with ICMP ECHO instead of ICMP TIMESTAMP
messages. It is useful with some destinations, which do not support
ICMP TIMESTAMP (f.e. Solaris <2.4).
Slightly different form of -o, namely it uses three-term
IP TIMESTAMP with prespecified hop addresses instead of four term one.
What flavor works better depends on target host. Particularly,
-o is better for Linux.
Some nodes (Cisco) use non-standard timestamps, which is allowed
by RFC, but makes timestamps mostly useless.
Some nodes generate messed timestamps (Solaris>2.4), when
run xntpd. Seems, its IP stack uses a corrupted clock source,
which is synchronized to time-of-day clock periodically and jumps
randomly making timestamps mostly useless. Good news is that you can
use NTP in this case, which is even better.
clockdiff shows difference in time modulo 24 days.
 ICMP ECHO,
RFC0792, page 14.
 ICMP TIMESTAMP,
RFC0792, page 16.
 IP TIMESTAMP option,
RFC0791, 3.1, page 16.
clockdiff was compiled by
<firstname.lastname@example.org>. It was based on code borrowed
from BSD timed daemon.
clockdiff requires CAP_NET_RAWIO capability
to be executed. It is safe to be used as set-uid root.
clockdiff is part of iputils package
and the latest versions are available in source form for anonymous ftp
- SEE ALSO
linux.jgfs.net manual pages