NAME
clockdiff - measure clock difference between hosts
SYNOPSIS
clockdiff [-o] [-o1] destination
DESCRIPTION
clockdiff Measures clock difference between us and destination with 1
msec resolution using ICMP TIMESTAMP [2] packets or, optionally, IP
TIMESTAMP option [3] option added to ICMP ECHO. [1]
OPTIONS
-o 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).
-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.
Particularly, -o is better for Linux.
WARNINGS
o Some nodes (Cisco) use non-standard timestamps, which is allowed by
RFC, but makes timestamps mostly useless.
o 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.
o clockdiff shows difference in time modulo 24 days.
SEE ALSO
ping(8), arping(8), tracepath(8).
REFERENCES
[1] ICMP ECHO, RFC0792, page 14.
[2] ICMP TIMESTAMP, RFC0792, page 16.
[3] IP TIMESTAMP option, RFC0791, 3.1, page 16.
AUTHOR
clockdiff was compiled by Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>. It
was based on code borrowed from BSD timed daemon. It is now maintained
by YOSHIFUJI Hideaki <yoshfuji@skbuff.net>.
SECURITY
clockdiff requires CAP_NET_RAWIO capability to be executed. It is safe
to be used as set-uid root.
AVAILABILITY
clockdiff is part of iputils package and the latest versions are
available in source form at http://www.skbuff.net/iputils/iputils-
current.tar.bz2.