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 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.

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 maintained
       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			  17 May 2016			  CLOCKDIFF(8)