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 option and argument.iso
-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.
[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.