clockdiff(category14-security-amp-firewalls.html) - phpMan

CLOCKDIFF(8)                        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 <kuznet AT ms2.ru>. It
       was based on code borrowed from BSD timed daemon.
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.
iputils s20180629                                                 CLOCKDIFF(8)