bionic (8) clockdiff.8.gz

Provided by: iputils-clockdiff_20161105-1ubuntu3_amd64 bug

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.