CLOCKDIFF(8) System Manager’s Manual: iputils CLOCKDIFF(8)
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. 
-o Use IP TIMESTAMP with ICMP ECHO instead of ICMP TIMESTAMP mes-
sages. It is useful with some destinations, which do not support
ICMP TIMESTAMP (f.e. Solaris <2.4).
-o1 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. Particu-
larly, -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 synchro-
nized 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.
ping(8), arping(8), tracepath(8).
 ICMP ECHO, RFC0792, page 14.
 ICMP TIMESTAMP, RFC0792, page 16.
 IP TIMESTAMP option, RFC0791, 3.1, page 16.
clockdiff was compiled by Alexey Kuznetsov <email@example.com>. 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 ftp://ftp.inr.ac.ru/ip-rout-
iputils-020927 07 April 2005 CLOCKDIFF(8)
Man(1) output converted with