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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  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

   * 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

   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-
   current.tar.bz2.



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