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

           • 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.

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 20250605                                                                                    CLOCKDIFF(8)