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      1 <refentry id="clockdiff">
      2 
      3 <refmeta>
      4 <refentrytitle>clockdiff</refentrytitle>
      5 <manvolnum>8</manvolnum>
      6 <refmiscinfo>iputils-&snapshot;</refmiscinfo>
      7 </refmeta>
      8 
      9 <refnamediv>
     10 <refname>clockdiff</refname>
     11 <refpurpose>measure clock difference between hosts</refpurpose>
     12 </refnamediv>
     13 
     14 <refsynopsisdiv>
     15 <cmdsynopsis>
     16 <command>clockdiff</command>
     17 <arg choice="opt"><option>-o</option></arg>
     18 <arg choice="opt"><option>-o1</option></arg>
     19 <arg choice="req"><replaceable/destination/</arg>
     20 </cmdsynopsis>
     21 </refsynopsisdiv>
     22 
     23 <refsect1><title>DESCRIPTION</title>
     24 <para>
     25 <command/clockdiff/ Measures clock difference between us and
     26 <replaceable/destination/ with 1 msec resolution using ICMP TIMESTAMP
     27 <link linkend="clockdiff.icmp-timestamp">[2]</link>
     28 packets or, optionally, IP TIMESTAMP option
     29 <link linkend="clockdiff.ip-timestamp">[3]</link>
     30 option added to ICMP ECHO.
     31 <link linkend="clockdiff.icmp-echo">[1]</link>
     32 </para>
     33 </refsect1>
     34 
     35 <refsect1><title>OPTIONS</title>
     36 
     37 <variablelist>
     38 
     39  <varlistentry>
     40   <term><option/-o/</term>
     41   <listitem><para>
     42 Use IP TIMESTAMP with ICMP ECHO instead of ICMP TIMESTAMP
     43 messages. It is useful with some destinations, which do not support
     44 ICMP TIMESTAMP (f.e. Solaris &lt;2.4).
     45   </para></listitem>
     46  </varlistentry>
     47 
     48  <varlistentry>
     49   <term><option/-o1/</term>
     50   <listitem><para>
     51 Slightly different form of <option/-o/, namely it uses three-term
     52 IP TIMESTAMP with prespecified hop addresses instead of four term one.
     53 What flavor works better depends on target host. Particularly,
     54 <option/-o/ is better for Linux.
     55   </para></listitem>
     56  </varlistentry>
     57 
     58 </variablelist>
     59 
     60 </refsect1>
     61 
     62 <refsect1><title>WARNINGS</title>
     63 <itemizedlist>
     64  <listitem><para>
     65 Some nodes (Cisco) use non-standard timestamps, which is allowed
     66 by RFC, but makes timestamps mostly useless.
     67  </para></listitem>
     68  <listitem><para>
     69 Some nodes generate messed timestamps (Solaris&gt;2.4), when
     70 run <command/xntpd/. Seems, its IP stack uses a corrupted clock source,
     71 which is synchronized to time-of-day clock periodically and jumps
     72 randomly making timestamps mostly useless. Good news is that you can
     73 use NTP in this case, which is even better.
     74  </para></listitem>
     75  <listitem><para>
     76 <command/clockdiff/ shows difference in time modulo 24 days.
     77  </para></listitem>
     78 </itemizedlist>
     79 
     80 </refsect1>
     81 
     82 <refsect1><title>SEE ALSO</title>
     83 <para>
     84 <link linkend="ping">
     85 <citerefentry><refentrytitle/ping/<manvolnum/8/</citerefentry></link>,
     86 <link linkend="arping">
     87 <citerefentry><refentrytitle/arping/<manvolnum/8/</citerefentry></link>,
     88 <link linkend="tracepath">
     89 <citerefentry><refentrytitle/tracepath/<manvolnum/8/</citerefentry></link>.
     90 </para>
     91 </refsect1>
     92 
     93 <refsect1><title>REFERENCES</title>
     94 <para>
     95 [1] <anchor id="clockdiff.icmp-echo">ICMP ECHO,
     96 <ulink url="http://tools.ietf.org/rfc/rfc792.txt">
     97 RFC0792, page 14</ulink>.
     98 </para>
     99 <para>
    100 [2] <anchor id="clockdiff.icmp-timestamp">ICMP TIMESTAMP,
    101 <ulink url="http://tools.ietf.org/rfc/rfc792.txt">
    102 RFC0792, page 16</ulink>.
    103 </para>
    104 <para>
    105 [3] <anchor id="clockdiff.ip-timestamp">IP TIMESTAMP option,
    106 <ulink url="http://tools.ietf.org/rfc/rfc791.txt">
    107 RFC0791, 3.1, page 16</ulink>.
    108 </para>
    109 </refsect1>
    110 
    111 <refsect1><title>AUTHOR</title>
    112 <para>
    113 <command/clockdiff/ was compiled by
    114 <ulink url="mailto:kuznet (a] ms2.inr.ac.ru">Alexey Kuznetsov
    115 &lt;kuznet (a] ms2.inr.ac.ru&gt;</ulink>. It was based on code borrowed
    116 from BSD <command/timed/ daemon.
    117 It is now maintained by
    118 <ulink url="mailto:yoshfuji (a] skbuff.net">YOSHIFUJI Hideaki
    119 &lt;yoshfuji (a] skbuff.net&gt;</ulink>.
    120 </para>
    121 </refsect1>
    122 
    123 <refsect1><title>SECURITY</title>
    124 <para>
    125 <command/clockdiff/ requires <constant/CAP_NET_RAW/ capability
    126 to be executed. It is safe to be used as set-uid root.
    127 </para>
    128 </refsect1>
    129 
    130 <refsect1><title>AVAILABILITY</title>
    131 <para>
    132 <command/clockdiff/ is part of <filename/iputils/ package
    133 and the latest versions are  available in source form at
    134 <ulink url="http://www.skbuff.net/iputils/iputils-current.tar.bz2">
    135 http://www.skbuff.net/iputils/iputils-current.tar.bz2</ulink>.
    136 </para>
    137 </refsect1>
    138 
    139 <![IGNORE[
    140 <refsect1><title>COPYING</title>
    141 <para>
    142 <literallayout>
    143 This documentation is free software; you can redistribute
    144 it and/or modify it under the terms of the GNU General Public
    145 License Version 2.
    146 
    147 This program is distributed in the hope that it will be
    148 useful, but WITHOUT ANY WARRANTY; without even the implied
    149 warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
    150 See the GNU General Public License for more details.
    151  
    152 For more details see the file COPYING in the source
    153 distribution of Linux kernel of version 2.4.
    154 </literallayout>
    155 </para>
    156 </refsect1>
    157 ]]>
    158 
    159 
    160 
    161 </refentry>
    162