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

       clockdiff - measure clock difference between hosts

       clockdiff [ -o]  [ -o1]  destination

       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]

       -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.

       ? 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.

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

       [1] ICMP ECHO, RFC0792, page 14.

       [2] ICMP TIMESTAMP, RFC0792, page 16.

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

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

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

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

iputils-071127                   22 March 2017                    CLOCKDIFF(8)