freebsd-dev/contrib/ntp/html/ntptrace.htm
2001-08-29 14:35:15 +00:00

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<title>ntptrace - trace a chain of NTP servers back to the primary
source</title>
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<h3><tt>ntptrace</tt> - trace a chain of NTP servers back to the
primary source</h3>
<img align="left" src="pic/alice13.gif" alt="gif"><a href=
"http://www.eecis.udel.edu/~mills/pictures.htm">from <i>Alice's
Adventures in Wonderland</i>, Lewis Carroll</a>
<p>The rabbit knows the way back.<br clear="left">
</p>
<hr>
<h4>Synopsis</h4>
<tt>ntptrace [ -vdn ] [ -r <i>retries</i> ] [ -t <i>timeout</i> ] [
<i>server</i> ]</tt>
<h4>Description</h4>
<p><tt>ntptrace</tt> determines where a given Network Time Protocol
(NTP) server gets its time from, and follows the chain of NTP
servers back to their master time source. If given no arguments, it
starts with <tt>localhost</tt>. Here is an example of the output
from <tt>ntptrace</tt>:</p>
<pre>
% ntptrace
localhost: stratum 4, offset 0.0019529, synch distance 0.144135
server2ozo.com: stratum 2, offset 0.0124263, synch distance 0.115784
usndh.edu: stratum 1, offset 0.0019298, synch distance 0.011993, refid
'WWVB'
</pre>
On each line, the fields are (left to right): the host name, the
host stratum, the time offset between that host and the local host
(as measured by <tt>ntptrace</tt>; this is why it is not always
zero for "<tt>localhost</tt>"), the host synchronization distance,
and (only for stratum-1 servers) the reference clock ID. All times
are given in seconds. Note that the stratum is the server hop count
to the primary source, while the synchronization distance is the
estimated error relative to the primary source. These terms are
precisely defined in RFC-1305.
<h4>Options</h4>
<dl>
<dt><tt>-d</tt></dt>
<dd>Turns on some debugging output.</dd>
<dt><tt>-n</tt></dt>
<dd>Turns off the printing of host names; instead, host IP
addresses are given. This may be useful if a nameserver is
down.</dd>
<dt><tt>-r <i>retries</i></tt></dt>
<dd>Sets the number of retransmission attempts for each host
(default = 5).</dd>
<dt><tt>-t <i>timeout</i></tt></dt>
<dd>Sets the retransmission timeout (in seconds) (default =
2).</dd>
<dt><tt>-v</tt></dt>
<dd>Prints verbose information about the NTP servers.</dd>
</dl>
<h4>Bugs</h4>
This program makes no attempt to improve accuracy by doing multiple
samples.
<hr>
<a href="index.htm"><img align="left" src="pic/home.gif" alt=
"gif"></a>
<address><a href="mailto:mills@udel.edu">David L. Mills
&lt;mills@udel.edu&gt;</a></address>
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