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162 lines
4.5 KiB
162 lines
4.5 KiB
<refentry id="clockdiff">
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<refmeta>
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<refentrytitle>clockdiff</refentrytitle>
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<manvolnum>8</manvolnum>
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<refmiscinfo>iputils-&snapshot;</refmiscinfo>
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</refmeta>
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<refnamediv>
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<refname>clockdiff</refname>
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<refpurpose>measure clock difference between hosts</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<cmdsynopsis>
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<command>clockdiff</command>
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<arg choice="opt"><option>-o</option></arg>
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<arg choice="opt"><option>-o1</option></arg>
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<arg choice="req"><replaceable/destination/</arg>
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</cmdsynopsis>
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</refsynopsisdiv>
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<refsect1><title>DESCRIPTION</title>
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<para>
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<command/clockdiff/ Measures clock difference between us and
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<replaceable/destination/ with 1 msec resolution using ICMP TIMESTAMP
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<link linkend="clockdiff.icmp-timestamp">[2]</link>
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packets or, optionally, IP TIMESTAMP option
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<link linkend="clockdiff.ip-timestamp">[3]</link>
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option added to ICMP ECHO.
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<link linkend="clockdiff.icmp-echo">[1]</link>
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</para>
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</refsect1>
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<refsect1><title>OPTIONS</title>
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<variablelist>
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<varlistentry>
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<term><option/-o/</term>
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<listitem><para>
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Use IP TIMESTAMP with ICMP ECHO instead of ICMP TIMESTAMP
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messages. It is useful with some destinations, which do not support
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ICMP TIMESTAMP (f.e. Solaris <2.4).
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</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option/-o1/</term>
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<listitem><para>
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Slightly different form of <option/-o/, namely it uses three-term
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IP TIMESTAMP with prespecified hop addresses instead of four term one.
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What flavor works better depends on target host. Particularly,
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<option/-o/ is better for Linux.
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</para></listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1><title>WARNINGS</title>
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<itemizedlist>
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<listitem><para>
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Some nodes (Cisco) use non-standard timestamps, which is allowed
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by RFC, but makes timestamps mostly useless.
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</para></listitem>
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<listitem><para>
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Some nodes generate messed timestamps (Solaris>2.4), when
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run <command/xntpd/. Seems, its IP stack uses a corrupted clock source,
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which is synchronized to time-of-day clock periodically and jumps
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randomly making timestamps mostly useless. Good news is that you can
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use NTP in this case, which is even better.
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</para></listitem>
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<listitem><para>
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<command/clockdiff/ shows difference in time modulo 24 days.
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</para></listitem>
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</itemizedlist>
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</refsect1>
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<refsect1><title>SEE ALSO</title>
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<para>
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<link linkend="ping">
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<citerefentry><refentrytitle/ping/<manvolnum/8/</citerefentry></link>,
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<link linkend="arping">
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<citerefentry><refentrytitle/arping/<manvolnum/8/</citerefentry></link>,
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<link linkend="tracepath">
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<citerefentry><refentrytitle/tracepath/<manvolnum/8/</citerefentry></link>.
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</para>
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</refsect1>
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<refsect1><title>REFERENCES</title>
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<para>
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[1] <anchor id="clockdiff.icmp-echo">ICMP ECHO,
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<ulink url="http://tools.ietf.org/rfc/rfc792.txt">
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RFC0792, page 14</ulink>.
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</para>
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<para>
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[2] <anchor id="clockdiff.icmp-timestamp">ICMP TIMESTAMP,
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<ulink url="http://tools.ietf.org/rfc/rfc792.txt">
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RFC0792, page 16</ulink>.
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</para>
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<para>
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[3] <anchor id="clockdiff.ip-timestamp">IP TIMESTAMP option,
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<ulink url="http://tools.ietf.org/rfc/rfc791.txt">
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RFC0791, 3.1, page 16</ulink>.
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</para>
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</refsect1>
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<refsect1><title>AUTHOR</title>
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<para>
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<command/clockdiff/ was compiled by
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<ulink url="mailto:kuznet@ms2.inr.ac.ru">Alexey Kuznetsov
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<kuznet@ms2.inr.ac.ru></ulink>. It was based on code borrowed
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from BSD <command/timed/ daemon.
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It is now maintained by
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<ulink url="mailto:yoshfuji@skbuff.net">YOSHIFUJI Hideaki
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<yoshfuji@skbuff.net></ulink>.
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</para>
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</refsect1>
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<refsect1><title>SECURITY</title>
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<para>
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<command/clockdiff/ requires <constant/CAP_NET_RAW/ capability
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to be executed. It is safe to be used as set-uid root.
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</para>
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</refsect1>
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<refsect1><title>AVAILABILITY</title>
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<para>
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<command/clockdiff/ is part of <filename/iputils/ package
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and the latest versions are available in source form at
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<ulink url="http://www.skbuff.net/iputils/iputils-current.tar.bz2">
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http://www.skbuff.net/iputils/iputils-current.tar.bz2</ulink>.
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</para>
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</refsect1>
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<![IGNORE[
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<refsect1><title>COPYING</title>
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<para>
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<literallayout>
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This documentation is free software; you can redistribute
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it and/or modify it under the terms of the GNU General Public
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License Version 2.
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This program is distributed in the hope that it will be
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useful, but WITHOUT ANY WARRANTY; without even the implied
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warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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See the GNU General Public License for more details.
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For more details see the file COPYING in the source
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distribution of Linux kernel of version 2.4.
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</literallayout>
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</para>
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</refsect1>
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]]>
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</refentry>
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