CLOCKDIFF(8)          System Manager's Manual: iputils          CLOCKDIFF(8)

NAME         top

       clockdiff - measure clock difference between hosts

SYNOPSIS         top

       clockdiff [-o] [-o1] destination

DESCRIPTION         top

       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         top

       -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         top

       · 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.

SEE ALSO         top

       ping(8), arping(8), tracepath(8).

REFERENCES         top

       [1] ICMP ECHO, RFC0792, page 14.

       [2] ICMP TIMESTAMP, RFC0792, page 16.

       [3] IP TIMESTAMP option, RFC0791, 3.1, page 16.

AUTHOR         top

       clockdiff was compiled by Alexey Kuznetsov <>. It
       was based on code borrowed from BSD timed daemon.  It is now
       maintained by YOSHIFUJI Hideaki <>.

SECURITY         top

       clockdiff requires CAP_NET_RAW capability to be executed. It is safe
       to be used as set-uid root.

AVAILABILITY         top

       clockdiff is part of iputils package and the latest versions are
       available in source form at

COLOPHON         top

       This page is part of the iputils (IP utilities) project.  Information
       about the project can be found at ⟨⟩.
       If you have a bug report for this manual page, send it to,  This page was obtained
       from the project's upstream Git repository 
       ⟨git://⟩ on 2017-07-05.  If you
       discover any rendering problems in this HTML version of the page, or
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       or you have corrections or improvements to the information in this
       COLOPHON (which is not part of the original manual page), send a mail

iputils-151218                  05 July 2017                    CLOCKDIFF(8)

Pages that refer to this page: arping(8)