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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  destina‐
              tions, 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
       · Some  nodes  (Cisco)  use non-standard timestamps, which is allowed by RFC, but makes timestamps mostly use‐
         less.

       · 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
       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 <[email protected]>. It was based  on  code  borrowed  from  BSD
       timed daemon.  It is now maintained by YOSHIFUJI Hideaki <[email protected]>.

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-current.tar.bz2.



iputils-160308                                                                                           CLOCKDIFF(8)