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diff --git a/contrib/ntp/html/driver1.htm b/contrib/ntp/html/driver1.htm index 1f88e7d..b70010f 100644 --- a/contrib/ntp/html/driver1.htm +++ b/contrib/ntp/html/driver1.htm @@ -1,157 +1,157 @@ -<HTML> -<HEAD> - <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> -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>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>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>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>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>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>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. -<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> - - -<P>Additional Information - -<P><A HREF="refclock.htm">Reference Clock Drivers</A></DL> - -<HR> -<ADDRESS> -David L. Mills (mills@udel.edu)</ADDRESS> - -</BODY> -</HTML> +<!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> + |
