199 lines
12 KiB
HTML
199 lines
12 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<html>
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<head>
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<meta http-equiv="content-type" content="text/html;charset=iso-8859-1">
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<meta name="generator" content="HTML Tidy, see www.w3.org">
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<title>Server Options</title>
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<link href="scripts/style.css" type="text/css" rel="stylesheet">
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</head>
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<body>
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<h3>Server Options</h3>
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<img src="pic/boom3a.gif" alt="gif" align="left"><a href="http://www.eecis.udel.edu/~mills/pictures.html">from <i>Pogo</i>,
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Walt Kelly</a>
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<p>The chicken is getting configuration advice.</p>
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<p>Last update:
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<!-- #BeginDate format:En2m -->25-Nov-2009 4:46<!-- #EndDate -->
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</p>
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<br clear="left">
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<h4>Related Links</h4>
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<script type="text/javascript" language="javascript" src="scripts/command.txt"></script>
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<script type="text/javascript" language="javascript" src="scripts/confopt.txt"></script>
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<h4>Table of Contents</h4>
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<ul>
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<li class="inline"><a href="#cfg">Configuration Commands</a></li>
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<li class="inline"><a href="#opt">Command Options</a></li>
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<li class="inline"><a href="#aux">Auxilliary Commands</a></li>
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<li class="inline"><a href="#bug">Bugs</a></li>
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</ul>
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<hr>
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<p>Following is a description of the configuration commands in NTPv4. There are
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two classes of commands, configuration commands that configure an association
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with a remote server, peer or reference clock, and auxilliary commands that
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specify environmental variables that control various related operations. </p>
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<p>The various modes described on the <a href="assoc.html">Association Management</a> page
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are determined by the command keyword and the DNS name or IP address. Addresses
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are classed by type as (s) a remote server or peer (IPv4 class A, B and C),
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(b) the IP broadcast address of a local interface, (m) a multicast address (IPv4
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class D), or (r) a reference clock address (127.127.x.x). For type m addresses
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the IANA has assigned the multicast group address IPv4 224.0.1.1 and IPv6 ff05::101
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(site local) exclusively to NTP, but other nonconflicting addresses can be used. </p>
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<p>If the Basic Socket Interface Extensions for IPv6 (RFC-2553) is detected,
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support for the IPv6 address family is generated in addition to the default
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IPv4 address family. IPv6 addresses can be identified by the presence of colons ":" in
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the address field. IPv6 addresses can be used almost everywhere where IPv4 addresses
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can be used, with the exception of reference clock addresses, which are always
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IPv4. Note that in contexts where a host name is expected, a <tt>-4</tt> qualifier
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preceding the host name forces DNS resolution to the IPv4 namespace, while a <tt>-6</tt> qualifier
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forces DNS resolution to the IPv6 namespace.</p>
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<h4 id="cfg">Configuration Commands</h4>
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<dl>
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<dt id="server"><tt>server <i>address</i> [options ...]</tt><br>
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<tt>peer <i>address</i> [options ...]</tt><br>
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<tt>broadcast <i>address</i> [options ...]</tt><br>
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<tt>manycastclient <i>address</i> [options ...]</tt><br>
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<tt>pool <i>address</i> [options ...]</tt><br>
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<tt>unpeer [<i>address</i> | <i>associd</i>]</tt></dt>
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<dd>These commands specify the time server name or address to be used and the
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mode in which to operate. The <i>address</i> can be either a DNS name or a
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IPv4 or IPv6 address in standard notation. In general, multiple commands of
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each type can be used for different server and peer addresses or multicast
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groups.
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<dl>
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<dt><tt>server</tt></dt>
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<dd>For type s and r addresses (only), this command mobilizes a persistent
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client mode association with the specified remote server or local reference
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clock. If the <tt>preempt</tt> flag is specified, a preemptable client mode
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association is mobilized instead.</dd>
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<dt><tt>peer</tt></dt>
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<dd>For type s addresses (only), this command mobilizes a persistent symmetric-active
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mode association with the specified remote peer.</dd>
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<dt><tt>broadcast</tt></dt>
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<dd>For type b and m addressees (only), this command mobilizes a persistent
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broadcast or multicast server mode association. Note that type
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b messages go only to the interface specified, but type m messages go to
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all interfaces.</dd>
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<dt><tt>manycastclient</tt></dt>
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<dd>For type m addresses (only), this command mobilizes a manycast client
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mode association for the multicast group address specified. In this mode
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the address must match the address specified on the <tt>manycastserver</tt> command
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of one or more designated manycast servers.</dd>
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<dt><tt>pool</tt></dt>
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<dd>For type s messages (only) this command mobilizes a client mode association
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for servers implementing the pool automatic server discovery scheme described
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on the <a href="assoc.html">Association Management</a> page. The address
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is a DNS name in the form <tt><i>area</i>.pool.ntp.org</tt>, where <tt><i>area</i></tt> is
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a qualifier designating the server geographic area such as <tt>us</tt> or <tt>europe</tt>.</dd>
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<dt><tt>unpeer</tt></dt>
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<dd>This command removes a previously configured association. An address or association ID can
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be used to identify the association. Either an IP address or DNS name can be used. This
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command is most useful when supplied via <tt><a href="ntpq.html">ntpq</a></tt> runtime
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configuration commands <tt>:config</tt> and <tt>config-from-file</tt>.</dd>
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</dl></dd>
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</dl>
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<h4 id="opt">Command Options</h4>
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<dl>
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<dt><tt>autokey</tt></dt>
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<dd>Send and receive packets authenticated by the Autokey scheme described
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in the <a href="authopt.html">Authentication Options</a> page. This option
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is mutually exclusive with the <tt>key</tt> option.</dd>
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<dt><tt>burst</tt></dt>
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<dd>When the server is reachable, send a burst of eight packets instead of the
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usual one. The packet spacing is normally 2 s; however, the spacing between
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the first and second packets can be changed with the <a href="miscopt.html"><tt>calldelay</tt></a> command
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to allow additional time for a modem or ISDN call to complete. This option
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is valid only with the <tt>server</tt> command and type s addressesa.
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It is a recommended option when the <tt>maxpoll</tt> option is greater than
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10 (1024 s).</dd>
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<dt><tt>iburst</tt></dt>
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<dd>When the server is unreachable, send a burst of eight packets instead of
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the usual one. The packet spacing is normally 2 s; however, the spacing between
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the first and second packets can be changed with the <a href="miscopt.html"><tt>calldelay</tt></a> command
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to allow additional time for a modem or ISDN call to complete. This option
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is valid only with the <tt>server</tt> command and type s addresses. It is
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a recommended option with this command.</dd>
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<dt><tt>key</tt> <i><tt>key</tt></i></dt>
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<dd>Send and receive packets authenticated by the symmetric key scheme described
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in the <a href="authopt.html">Authentication Options</a> page.
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The <i><tt>key</tt></i> specifies the key identifier with values from 1 to
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65534, inclusive. This option is mutually exclusive with the <tt>autokey</tt> option.</dd>
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<dt><tt>minpoll <i>minpoll<br>
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</i></tt><tt>maxpoll <i>maxpoll</i></tt></dt>
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<dd>These options specify the minimum and maximum poll intervals for NTP messages,
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in seconds as a power of two. The maximum poll interval defaults to 10
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(1024 s), but can be increased by the <tt>maxpoll</tt> option to an upper limit
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of 17 (36 h). The minimum poll interval defaults to 6 (64 s), but can
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be decreased by the <tt>minpoll</tt> option to a lower limit of 3 (8 s).</dd>
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<dt><tt>mode <i>option</i></tt></dt>
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<dd>Pass the <tt><i>option</i></tt> to a reference clock driver, where <tt><i>option</i></tt> is
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an integer in the range from 0 to 255, inclusive. This option is valid
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only with type r addresses.</dd>
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<dt><tt>noselect</tt></dt>
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<dd>Marks the server or peer to be ignored by the selection algorithm but visible
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to the monitoring program. This option is ignored with the <tt>broadcast</tt> command.</dd>
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<dt><tt>preempt</tt></dt>
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<dd>Specifies the association as preemptable rather than the default persistent.
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This option is ignored with the <tt>broadcast</tt> command and is most useful
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with the <tt>manycastclient</tt> and <tt>pool</tt> commands.</dd>
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<dt><tt>prefer</tt></dt>
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<dd>Mark the server as preferred. All other things being equal, this host will
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be chosen for synchronization among a set of correctly operating hosts. See
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the <a href="prefer.html">Mitigation Rules and the <tt>prefer</tt> Keyword</a> page
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for further information. This option is valid only with the <tt>server</tt> and <tt>peer</tt> commands.</dd>
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<dt><tt>true</tt></dt>
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<dd>Mark the association to assume truechimer status; that is, always survive
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the selection and clustering algorithms. This option can be used with any association,
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but is most useful for reference clocks with large jitter on the serial port
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and precision pulse-per-second (PPS) signals. Caution: this option defeats
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the algorithms designed to cast out falsetickers and can allow these sources
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to set the system clock. This option is valid only with the <tt>server</tt> and <tt>peer</tt> commands.</dd>
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<dt><tt>ttl <i>ttl</i></tt></dt>
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<dd>This option specifies the time-to-live <i><tt>ttl</tt></i> for the <tt>broadcast</tt> command
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and the maximum <i><tt>ttl</tt></i> for the expanding ring search used by the <tt>manycastclient</tt> command.
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Selection of the proper value, which defaults to 127, is something of a black art and should be coordinated with the network administrator. This option is invalid with type r addresses.</dd>
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<dt><tt>version <i>version</i></tt></dt>
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<dd>Specifies the version number to be used f
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or outgoing NTP packets. Versions
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1-4 are the choices, with version 4 the default.</dd>
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<dt><tt>xleave</tt></dt>
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<dd>Operate in interleaved mode (symmetric and broadcast modes only). (see <a href="xleave.html">NTP
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Interleaved Modes</a>)</dd>
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</dl>
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<h4 id="aux">Auxilliary Commands</h4>
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<dl>
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<dt id="broadcastclient"><tt>broadcastclient</tt></dt>
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<dd>Enable reception of broadcast server messages to any local interface (type
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b address). Ordinarily, upon receiving a broadcast message for the first
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time, the broadcast client measures the nominal server propagation delay using
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a brief client/server exchange, after which it continues in listen-only mode.
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If a nonzero value is specified in the <tt>broadcastdelay</tt> command, the
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value becomes the delay and the volley is not executed. Note: the <tt>novolley</tt> option
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has been deprecated for future enhancements. Note that, in order to avoid
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accidental or malicious disruption in this mode, both the server and client
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should operate using symmetric key or public key authentication as described
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in the <a href="authopt.html">Authentication
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Options</a> page. Note that the <tt>novolley</tt> keyword is incompatible with
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public key authentication.</dd>
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<dt id="manycastserver"><tt>manycastserver <i>address</i> [...]</tt></dt>
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<dd>Enable reception of manycast client messages (type m)to the multicast group
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address(es) (type m) specified. At least one address is required. Note that,
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in order to avoid accidental or malicious disruption, both the server and client
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should operate using symmetric key or public key authentication as described
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in the <a href="authopt.html">Authentication Options</a> page.</dd>
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<dt id="multicastclient"><tt>multicastclient <i>address</i> [...]</tt></dt>
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<dd>Enable reception of multicast server messages to the multicast group address(es)
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(type m) specified. Upon receiving a message for the first time, the multicast
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client measures the nominal server propagation delay using a brief client/server
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exchange with the server, then enters the broadcast client mode, in which it
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synchronizes to succeeding multicast messages. Note that, in order to avoid
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accidental or malicious disruption in this mode, both the server and client
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should operate using symmetric key or public key authentication as described
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in the <a href="authopt.html">Authentication Options</a> page.</dd>
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</dl>
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<h4 id="bug">Bugs</h4>
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<p>The syntax checking is not picky; some combinations of ridiculous and even
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hilarious options and modes may not be detected.</p>
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<hr>
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<script type="text/javascript" language="javascript" src="scripts/footer.txt"></script>
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</body>
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</html>
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