1CLOCKDIFF(8)           System Manager's Manual: iputils           CLOCKDIFF(8)
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NAME

6       clockdiff - measure clock difference between hosts
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SYNOPSIS

9       clockdiff [-o] [-o1] destination
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DESCRIPTION

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

18       -o     Use  IP  TIMESTAMP with ICMP ECHO instead of ICMP TIMESTAMP mes‐
19              sages. It is useful with some destinations, which do not support
20              ICMP TIMESTAMP (f.e. Solaris <2.4).
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22       -o1    Slightly  different  form  of  -o,  namely it uses three-term IP
23              TIMESTAMP with prespecified hop addresses instead of  four  term
24              one.   What flavor works better depends on target host. Particu‐
25              larly, -o is better for Linux.
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WARNINGS

28       · Some nodes (Cisco) use non-standard timestamps, which is  allowed  by
29         RFC, but makes timestamps mostly useless.
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31       · Some  nodes generate messed timestamps (Solaris>2.4), when run xntpd.
32         Seems, its IP stack uses a corrupted clock source, which is  synchro‐
33         nized  to  time-of-day  clock  periodically and jumps randomly making
34         timestamps mostly useless. Good news is that you can use NTP in  this
35         case, which is even better.
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37       · clockdiff shows difference in time modulo 24 days.
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SEE ALSO

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

43       [1] ICMP ECHO, RFC0792, page 14.
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45       [2] ICMP TIMESTAMP, RFC0792, page 16.
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47       [3] IP TIMESTAMP option, RFC0791, 3.1, page 16.
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AUTHOR

50       clockdiff  was  compiled by Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>. It
51       was based on code borrowed from BSD timed daemon.  It is now maintained
52       by YOSHIFUJI Hideaki <yoshfuji@skbuff.net>.
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SECURITY

55       clockdiff requires CAP_NET_RAW capability to be executed. It is safe to
56       be used as set-uid root.
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AVAILABILITY

59       clockdiff is part of  iputils  package  and  the  latest  versions  are
60       available  in source form at http://www.skbuff.net/iputils/iputils-cur‐
61       rent.tar.bz2.
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65iputils-160308                                                    CLOCKDIFF(8)
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