CLOCKDIFF(8) System Manager's Manual: iputils CLOCKDIFF(8)
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 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.
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 main-
tained by YOSHIFUJI Hideaki <yoshfuji@skbuff.net>.
SECURITY
clockdiff requires CAP_NET_RAW 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-cur-
rent.tar.bz2.
iputils-121221 10 June 2014 CLOCKDIFF(8)