clockdiff.sgml revision 313379eb6b9da55f7371adef39a92153a0707d4a 
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>
28packets or, optionally, IP TIMESTAMP option
29<link linkend="clockdiff.ip-timestamp">[3]</link>
30option 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>
42Use IP TIMESTAMP with ICMP ECHO instead of ICMP TIMESTAMP
43messages. It is useful with some destinations, which do not support
44ICMP TIMESTAMP (f.e. Solaris &lt;2.4).
45  </para></listitem>
46 </varlistentry>
47
48 <varlistentry>
49  <term><option/-o1/</term>
50  <listitem><para>
51Slightly different form of <option/-o/, namely it uses three-term
52IP TIMESTAMP with prespecified hop addresses instead of four term one.
53What 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>
65Some nodes (Cisco) use non-standard timestamps, which is allowed
66by RFC, but makes timestamps mostly useless.
67 </para></listitem>
68 <listitem><para>
69Some nodes generate messed timestamps (Solaris&gt;2.4), when
70run <command/xntpd/. Seems, its IP stack uses a corrupted clock source,
71which is synchronized to time-of-day clock periodically and jumps
72randomly making timestamps mostly useless. Good news is that you can
73use 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">
97RFC0792, 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">
102RFC0792, 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">
107RFC0791, 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&lt;kuznet@ms2.inr.ac.ru&gt;</ulink>. It was based on code borrowed
116from BSD <command/timed/ daemon.
117It is now maintained by
118<ulink url="mailto:yoshfuji@skbuff.net">YOSHIFUJI Hideaki
119&lt;yoshfuji@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
126to 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
133and the latest versions are  available in source form at
134<ulink url="http://www.skbuff.net/iputils/iputils-current.tar.bz2">
135http://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>
143This documentation is free software; you can redistribute
144it and/or modify it under the terms of the GNU General Public
145License Version 2.
146
147This program is distributed in the hope that it will be
148useful, but WITHOUT ANY WARRANTY; without even the implied
149warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
150See the GNU General Public License for more details.
151 
152For more details see the file COPYING in the source
153distribution of Linux kernel of version 2.4.
154</literallayout>
155</para>
156</refsect1>
157]]>
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161</refentry>
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