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 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
       o Some nodes (Cisco) use non-standard timestamps, which is allowed by RFC, but makes timestamps mostly useless.

       o 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.

       o 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 <kuznetATms2.ru>. It was based on code borrowed from BSD  timed  daemon.
       It is now maintained by YOSHIFUJI Hideaki <yoshfujiATskbuff.net>.

SECURITY
       clockdiff requires CAP_NET_RAWIO 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-100418                                            13 July 2010                                              CLOCKDIFF(8)