Manpages - 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] 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.