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CLOCKDIFF(8) iputils CLOCKDIFF(8)
clockdiff - measure clock difference between hosts
clockdiff [-o] [-o1] [--time-format ctime iso] [-V] {destination}
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]
-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.
• 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.
ping(8), arping(8), tracepath(8).
[1] ICMP ECHO, RFC0792, page 14. [2] ICMP TIMESTAMP, RFC0792, page 16. [3] IP TIMESTAMP option, RFC0791, 3.1, page 16.
clockdiff was compiled by Alexey Kuznetsov <[email protected]>. It was based on code borrowed from BSD timed daemon.
clockdiff requires CAP_NET_RAW and CAP_SYS_NICE capabilities to be executed. It is safe to be used as set-uid root.
clockdiff is part of iputils package.
This page is part of the iputils (IP utilities) project.
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iputils 20240117 CLOCKDIFF(8)
Pages that refer to this page: arping(8)