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Last update: 11-Nov-2011 1:25 UTC
Note: The NTP Version 4 software contained in this distribution is available without charge under the conditions set forth in the Copyright Notice.
This distribution is an implementation of RFC-5905 "Network Time Protocol Version 4: Protocol and Algorithms Specification".
NTP is widely used to synchronize a computer to Internet time servers or other sources, such as a radio or satellite receiver or telephone modem service. It can also be used as a server for dependent clients. It provides accuracies typically less than a millisecond on LANs and up to a few milliseconds on WANs. Typical NTP configurations utilize multiple redundant servers and diverse network paths in order to achieve high accuracy and reliability.
This distribution includes a simulation framework in which substantially all the runtime NTP operations and most features can be tested and evaluated. This has been very useful in exploring in vitro response to unusual circumstances or over time periods impractical in vivo. Details are on the Network Time Protocol (NTP) Simulator page.
A good deal of tutorial and directive information is available on the handbook pages. These should be read in conjunction with the command and option information available on the pages listed on the sitemap page.
NTP supports Unix, VMS and Windows (Vista, XP, Windows 7, NT4 and 2000) systems. The Building and Installing the Distribution page details the procedures for building and installing on a typical system. This distribution includes drivers for many radio and satellite receivers and telephone modem services in the US, Canada and Europe. A list of supported drivers is on the Reference Clock Drivers page. The default build includes the debugging options and all drivers that run on the target machine; however, options and drivers can be included or excluded using options on the Configuration Options page.
Like other things in modern Internet life, NTP problems can be devilishly intricate. This distribution includes a number of utilities designed to identify and repair problems using an integrated management protocol supported by the ntpq utility program.
The NTP Debugging Techniques and Hints and Kinks pages contain useful information for identifying problems and devising solutions. Additional information on reference clock driver construction and debugging is in the Debugging Hints for Reference Clock Drivers page.
Users are invited to report bugs and offer suggestions via the NTP Bug Reporting Procedures page.
The Site Map page contains a list of document collections arranged by topic. The Program Manual Pages collection may be the best place to start. The Command Index collection contains a list of all configuration file commands together with a short function description. A great wealth of additional information is available via the External Links collection, including a book and numerous background papers and briefing presentations.
Background information on computer network time synchronization is on the Executive Summary - Computer Network Time Synchronization page. Discussion on new features and interoperability with previous NTP versions is on the NTP Version 4 Release Notes page. Background information, bibliography and briefing slides suitable for presentations are on the Network Time Synchronization Research Project page. Additional information is at the NTP web site www.ntp.org.