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.