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diff --git a/html/driver1.htm b/html/driver1.htm new file mode 100644 index 000000000000..b70010fe583d --- /dev/null +++ b/html/driver1.htm @@ -0,0 +1,157 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 3.2//EN"> +<html> +<head> +<meta name="generator" content="HTML Tidy, see www.w3.org"> +<meta http-equiv="Content-Type" content= +"text/html; charset=iso-8859-1"> +<meta name="GENERATOR" content= +"Mozilla/4.01 [en] (Win95; I) [Netscape]"> +<title>Undisciplined Local Clock</title> +</head> +<body> +<h3>Undisciplined Local Clock</h3> + +<hr> +<h4>Synopsis</h4> + +Address: 127.127.1.<i>u</i> <br> +Reference ID: <tt>LCL</tt> <br> +Driver ID: <tt>LOCAL</tt> + +<h4>Description</h4> + +<p>This driver is intended for use in an isolated network where no +external source of synchronization such as a radio clock or modem +is available. It allows a designated time server to act as a +primary server to provide synchronization to other clients on the +network. Pick a machine that has a good clock oscillator (Digital +machines are good, Sun machines are not) and configure it with this +driver. Set the clock using the best means available, like +eyeball-and-wristwatch. Then, point all the other machines at this +one or use broadcast (not multicast) mode to distribute time.</p> + +<p>Another application for this driver is if a particular server +clock is to be used as the clock of last resort when all other +normal synchronization sources have gone away. This is especially +useful if that server has an ovenized oscillator. For this you +would configure this driver at a stratum greater than any other +likely sources of time (say 3 or 4) to prevent the server taking +over when legitimate sources are still available.</p> + +<p>A third application for this driver is when an external +discipline source is available, such as the NIST <tt>lockclock</tt> +program, which synchronizes the local clock via a telephone modem +and the NIST Automated Computer Time Service (ACTS), or the Digital +Time Synchronization Service (DTSS), which runs on DCE machines. In +this case the stratum should be set at zero, indicating a bona fide +stratum-1 source. In the case of DTSS, the local clock can have a +rather large jitter, depending on the interval between corrections +and the intrinsic frequency error of the clock oscillator. In +extreme cases, this can cause clients to exceed the 128-ms slew +window and drop off the NTP subnet.</p> + +<p>In the case where a NTP time server is synchronized to some +device or protocol that is not external to the NTP daemon itself, +some means should be provided to pass such things as error and +health values to the NTP daemon for dissemination to its clients. +If this is not done, there is a very real danger that the device or +protocol could fail and with no means to tell NTP clients of the +mishap. When ordinary Unix system calls like <tt>adjtime()</tt> are +used to discipline the kernel clock, there is no obvious way this +can be done without modifying the code for each case. However, when +a modified kernel with the <tt>ntp_adjtime()</tt> system call +is available, that routine can be used for the same purpose as the +<tt>adjtime()</tt> routine and in addition provided with the +estimated error, maximum error, and leap-indicator values. This is +the preferred way to synchronize the kernel clock and pass +information to the NTP clients.</p> + +<p>In the default mode the behavior of the clock selection +algorithm is modified when this driver is in use. The algorithm is +designed so that this driver will never be selected unless no other +discipline source is available. This can be overridden with the +<tt>prefer</tt> keyword of the <tt>server</tt> configuration +command, in which case only this driver will be selected for +synchronization and all other discipline sources will be ignored. +This behavior is intended for use when an external discipline +source controls the system clock. See the <a href="prefer.htm"> +Mitigation Rules and the <tt>prefer</tt> Keyword</a> page for a +detailed description of the exact behavior.</p> + +<p>The stratum for this driver is set at 3 by default, but can be +changed by the <tt>fudge</tt> configuration command and/or the <tt> +ntpdc</tt> utility. The reference ID is <tt>LCL</tt> by default, +but can be changed using the same mechanisms. <b>*NEVER*</b> +configure this driver to operate at a stratum which might possibly +disrupt a client with access to a bona fide primary server, unless +the local clock oscillator is reliably disciplined by another +source. <b>*NEVER NEVER*</b> configure a server which might devolve +to an undisciplined local clock to use multicast mode.</p> + +<p>This driver provides a mechanism to trim the local clock in both +time and frequency, as well as a way to manipulate the leap bits. +The <tt>fudge time1</tt> parameter adjusts the time (in seconds) +and the <tt>fudge time2</tt> parameter adjusts the frequency (in +parts per million). Both parameters are additive and operate only +once; that is, each command (as from <tt>ntpdc</tt>) adds signed +increments in time or frequency to the nominal local clock time and +frequency.</p> + +<h4>Monitor Data</h4> + +No <tt>filegen clockstats</tt> monitor data are produced by this +driver. + +<h4>Fudge Factors</h4> + +<dl> +<dt><tt>time1 <i>time</i></tt></dt> + +<dd>Specifies the time offset calibration factor, in seconds and +fraction, with default 0.0.</dd> + +<dt><tt>time2 <i>time</i></tt></dt> + +<dd>Specifies the frequency offset calibration factor, in parts per +million, with default 0.0.</dd> + +<dt><tt>stratum <i>number</i></tt></dt> + +<dd>Specifies the driver stratum, in decimal from 0 to 15, with +default 3.</dd> + +<dt><tt>refid <i>string</i></tt></dt> + +<dd>Specifies the driver reference identifier, an ASCII string from +one to four characters, with default <tt>LCL</tt>.</dd> + +<dt><tt>flag1 0 | 1</tt></dt> + +<dd>Not used by this driver.</dd> + +<dt><tt>flag2 0 | 1</tt></dt> + +<dd>Not used by this driver.</dd> + +<dt><tt>flag3 0 | 1</tt></dt> + +<dd>Not used by this driver.</dd> + +<dt><tt>flag4 0 | 1</tt></dt> + +<dd>Not used by this driver.</dd> +</dl> + +<p>Additional Information</p> + +<p><a href="refclock.htm">Reference Clock Drivers</a></p> + +<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 +<mills@udel.edu></a></address> +</body> +</html> + |