Lorenzo Colitti | 313379e | 2013-07-11 01:07:11 +0900 | [diff] [blame] | 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 <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>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@ms2.inr.ac.ru">Alexey Kuznetsov |
| 115 | <kuznet@ms2.inr.ac.ru></ulink>. It was based on code borrowed |
| 116 | from BSD <command/timed/ daemon. |
| 117 | It is now maintained by |
| 118 | <ulink url="mailto:yoshfuji@skbuff.net">YOSHIFUJI Hideaki |
| 119 | <yoshfuji@skbuff.net></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> |