1CLOCKDIFF(8)                        iputils                       CLOCKDIFF(8)
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NAME

6       clockdiff - measure clock difference between hosts
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SYNOPSIS

9       clockdiff [-o] [-o1] [--time-format ctime iso] [-V] {destination}
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DESCRIPTION

12       clockdiff Measures clock difference between us and destination with 1
13       msec resolution using ICMP TIMESTAMP [2] packets or, optionally, IP
14       TIMESTAMP option [3] added to ICMP ECHO. [1]
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OPTIONS

17       -o
18           Use IP TIMESTAMP with ICMP ECHO instead of ICMP TIMESTAMP messages.
19           It is useful with some destinations, which do not support ICMP
20           TIMESTAMP (f.e. Solaris <2.4).
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22       -o1
23           Slightly different form of -o, namely it uses three-term IP
24           TIMESTAMP with prespecified hop addresses instead of four term one.
25           What flavor works better depends on target host. Particularly, -o
26           is better for Linux.
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28       -T, --time-format ctime iso
29           Print time stamp in output either ISO-8601 format or classical
30           ctime format. The ctime format is default. The ISO time stamp
31           includes timezone, and is easier to parse.
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33       -I
34           Alias of --time-format iso option and argument.
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36       -h, --help
37           Print help and exit.
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39       -V, --version
40           Print version and exit.
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WARNINGS

43           • Some nodes (Cisco) use non-standard timestamps, which is allowed
44           by RFC, but makes timestamps mostly useless.
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46           • Some nodes generate messed timestamps (Solaris>2.4), when run
47           xntpd. Seems, its IP stack uses a corrupted clock source, which is
48           synchronized to time-of-day clock periodically and jumps randomly
49           making timestamps mostly useless. Good news is that you can use NTP
50           in this case, which is even better.
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52           • clockdiff shows difference in time modulo 24 days.
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SEE ALSO

55       ping(8), arping(8), tracepath(8).
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REFERENCES

58       [1] ICMP ECHO, RFC0792, page 14.
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60       [2] ICMP TIMESTAMP, RFC0792, page 16.
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62       [3] IP TIMESTAMP option, RFC0791, 3.1, page 16.
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AUTHOR

65       clockdiff was compiled by Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>. It
66       was based on code borrowed from BSD timed daemon.
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SECURITY

69       clockdiff requires CAP_NET_RAW and CAP_SYS_NICE capabilities to be
70       executed. It is safe to be used as set-uid root.
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AVAILABILITY

73       clockdiff is part of iputils package.
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77iputils 20221126                                                  CLOCKDIFF(8)
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