163 lines
7.9 KiB
HTML
163 lines
7.9 KiB
HTML
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<!-- $NetBSD: index.html,v 1.1 1998/12/30 20:20:35 mcr Exp $ -->
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<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML Strict//EN">
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<html><head><title>
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The Network Time Protocol (NTP) Distribution
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</title></head><body><h3>
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The Network Time Protocol (NTP) Distribution
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</h3><hr>
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<p><h4>Introduction</h4>
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<p>Note: The software contained in this distribution is available
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without charge under the conditions set forth in the <a href =
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"copyright.html"> Copyright Notice</a>.
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<p>The Network Time Protocol (NTP) is used to synchronize the time of a
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computer client or server to another server or reference time source,
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such as a radio or satellite receiver or modem. It provides client
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accuracies typically within a millisecond on LANs and up to a few tens
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of milliseconds on WANs relative to a primary server synchronized to
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Coordinated Universal Time (UTC) via a Global Positioning Service (GPS)
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receiver, for example. Typical NTP configurations utilize multiple
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redundant servers and diverse network paths, in order to achieve high
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accuracy and reliability. Some configurations include cryptographic
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authentication to prevent accidental or malicious protocol attacks.
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Information on the NTP architecture, protocol and algorithms can be
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found in the <a href = "biblio.html"> Further Information and
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Bibliography</a> page.
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<p><h4>Building and Installing NTP</h4>
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<p>The <a href = "build.html"> Building and Installing the Distribution
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</a> page presents an overview of the procedures for compiling the
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distribution and installing it on a typical client or server. The build
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procedures inspect the system hardware and software environment and
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automatically select the appropriate options for that environment. While
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these procedures work with most computers and operating systems marketed
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today, exceptions requiring manual intervention do exist, as documented
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in the <a href = "config.html"> Configuration Options </a>
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and <a href = "release.html"> Release Notes </a> pages.
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<p>Bringing up a NTP primary server requires a radio or satellite
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receiver or modem. The distribution includes hardware drivers for over
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two dozen radio clocks and modem services. A list of the particular
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receivers and modem drivers supported in the distribution is given in
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the <a href = "refclock.html"> Reference Clock Drivers </a> page. For
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most popular workstations marketed by DEC, Sun and Hewlett Packard, the
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automatic build procedures select all drivers that run on the target
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machine. While this increases the size of the executable binary
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somewhat, individual drivers can be included or excluded using special
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scripts.
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<p><h4>Configuring Clients and Servers</h4>
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<p>In order to participate in the existing NTP synchronization subnet
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and obtain accurate, reliable time, it is necessary to construct an
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appropriate configuration file, usually called <code>ntp.conf</code>,
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which establishes the servers and/or external receivers or modems to be
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used by this particular machine. Directions for constructing this file
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are in the <a href = "notes.html"> Notes on Configuring NTP and Setting
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up a NTP Subnet </a> page.
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<p>The most important factor in providing accurate, reliable time is the
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selection of modes and servers to be used in the configuration file. NTP
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support for one or more computers is normally engineered as part of the
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existing NTP synchronization subnet. The existing NTP subnet consists of
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a multiply redundant hierarchy of servers and clients, with each level
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in the hierarchy identified by stratum number. Primary servers operate
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at stratum one and provide synchronization to secondary servers
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operating at stratum two and so on to higher strata. In this hierarchy,
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clients are simply servers that have no dependents.
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<p>The NTP subnet presently includes over 50 public primary servers
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synchronized directly to UTC by radio, satellite or modem and located in
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North America, Europe and Asia. Normally, client workstations and
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servers with a relatively small number of clients do not synchronize to
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primary servers. There are about 100 public secondary servers
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synchronized to the primary servers and providing synchronization to a
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total in excess of 100,000 clients and servers in the Internet. The
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current lists are maintained in the <a href =
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"http://www.eecis.udel.edu/~mills/ntp/servers.html"> List of Public NTP
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Servers </a> page, which is updated frequently. There are numerous
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private primary and secondary servers not normally available to the
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public as well.
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<p><h4>Resolving Problems</h4>
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<p>Like other things Internet, the NTP synchronization subnets tend to
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be large and devilishly intricate, with many opportunities for
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misconfiguration and network problems. The NTP engineering model is
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specifically designed to help isolate and repair such problems using an
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integrated management protocol, together with a suite of monitoring and
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debugging tools. There is an optional data recording facility which can
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be used to record normal and aberrant operation, log problems to the
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system log facility, and retain records of client access. The <a href =
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"debug.html"> NTP Debugging Techniques </a> and <a href = "hints.html">
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Hints and Kinks </a>pages contain useful information for identifying
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problems and devising solutions.
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<p>Users are requested to report bugs, offer suggestions and contribute
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additions to this distribution. The <a href = "patches.html"> Patching
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Procedures </a> page suggests procedures which greatly simplify
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distribution updates, while the <a href = "porting.html"> Porting Hints
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</a> suggest ways to make porting this code to new hardware and
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operating systems easier. Additional information on reference clock
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driver construction and debugging can be found in the <a href =
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"refclock.html"> Reference Clock Drivers </a> page. Further information
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on NTP in the Internet can be found in the <a href =
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"http://www.eecis.udel.edu/~ntp"> NTP web page</a>.
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<p><h4>Program Manual Pages</h4>
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<p><a href = "xntpd.html"> <code>xntpd</code> - Network Time Protocol
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(NTP) daemon </a>
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<br><a href = "ntpq.html"> <code>ntpq</code> - standard NTP query
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program </a>
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<br><a href = "xntpdc.html"> <code>xntpdc</code> - special NTP query
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program </a>
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<br><a href = "ntpdate.html"> <code>ntpdate</code> - set the date and
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time via NTP </a>
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<br><a href = "ntptrace.html"> <code>ntptrace</code> - trace a chain of
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NTP servers back to the primary source </a>
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<br><a href = "tickadj.html"> <code>tickadj</code> - set time-related
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kernel variables </a>
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<br><a href = "ntptime.html"> <code>ntptime</code> - read kernel time
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variables </a>
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<br><a href = "authspeed.html"> <code>authspeed</code> - determine
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authentication delays </a>
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<br><a href = "authcert.html"> <code>authcert</code> - DES validation
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program </a>
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<br><a href = "md5cert.html"> <code>md5</code> - generate message digest
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</a>
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<p><h4>Supporting Documentation</h4>
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<p><a href = "copyright.html"> Copyright Notice </a>
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<br><a href = "notes.html"> Notes on Configuring NTP and Setting up a
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NTP Subnet </a>
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<br><a href = "release.html"> Release Notes </a>
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<br><a href = "build.html"> Building and Installing the Distribution
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</a>
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<br><a href = "config.html"> Configuration Options </a>
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<br><a href = "debug.html"> NTP Debugging Techniques </a>
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<br><a href = "refclock.html"> Reference Clock Drivers </a>
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<br><a href = "biblio.html"> Further Information and Bibliography
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</a>
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<br><a href = "patches.html"> Patching Procedures </a>
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<br><a href = "hints.html"> Hints and Kinks </a>
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<br><a href = "porting.html"> Porting Hints </a>
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<p><h4>Application Notes</h4>
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<p><a href = "prefer.html"> Mitigation Rules and the <code>prefer</code>
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Keyword </a>
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<br><a href = "gadget.html"> Gadget Box PPS Level Converter and CHU
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Modem </a>
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<br><a href = "irig.html"> IRIG Support Using Sun SPARC Audio </a>
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<br><a href = "measure.html"> Time and Time Interval Measurement with
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Application to Computer and Network Performance Evaluation </a>
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<br><a href = "kern.html"> A Kernel Model for Precision Timekeeping </a>
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<br><a href = "kernpps.html"> A Kernel Programming Interface for
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Precision Time Signals </a>
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<hr><address>David L. Mills (mills@udel.edu)</address></body></html>
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