CLOCKDIFF(8)                       iputils                      CLOCKDIFF(8)

NAME         top

       clockdiff - measure clock difference between hosts

SYNOPSIS         top

       clockdiff [-o] [-o1] [-V] {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

           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).

           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.

           Print version and exit.

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.

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.

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
       ⟨⟩ on 2019-05-09.  (At that
       time, the date of the most recent commit that was found in the repos‐
       itory was 2019-04-19.)  If you discover any rendering problems in
       this HTML version of the page, or you believe there is a better or
       more up-to-date source for the page, or you have corrections or
       improvements to the information in this COLOPHON (which is not part
       of the original manual page), send a mail to

iputils s20190324                                               CLOCKDIFF(8)

Pages that refer to this page: arping(8)