CLOCKDIFF(8)                        iputils                       CLOCKDIFF(8)

NAME
       clockdiff - measure clock difference between hosts

SYNOPSIS
       clockdiff [-o] [-o1] [--time-format ctime iso] [-V] {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] 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.

       -T, --time-format ctime iso
           Print time stamp in output either ISO-8601 format or classical
           ctime format. The ctime format is default. The ISO time stamp
           includes timezone, and is easier to parse.

       -I
           Alias of --time-format iso  option and argument.

       -h, --help
           Print help and exit.

       -V, --version
           Print version and exit.

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 <kuznet@ms2.inr.ac.ru>. It
       was based on code borrowed from BSD timed daemon.

SECURITY
       clockdiff requires CAP_NET_RAW and CAP_SYS_NICE capabilities to be
       executed. It is safe to be used as set-uid root.

AVAILABILITY
       clockdiff is part of iputils package.

iputils 20240117                                                  CLOCKDIFF(8)