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clockdiff − measure clock difference between hosts
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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] option 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 <kuznet@ms2.inr.ac.ru>. It was based on code borrowed from BSD timed daemon.
clockdiff requires CAP_NET_RAW capability to be executed. It is safe to be used as set−uid root.
clockdiff is part of iputils package.