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Notes for NTP Version 3
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This version operates in much the same manner as Version 2 with the
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following changes and additions:
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1. The protocol machinery operates in conformance with the RFC1305 NTP
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Version 3 specification. The most visible characteristic of this
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version is that the poll intervals for all polls, even selected
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ones, is significantly increased. This is especially desirable when
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serving a large client population. This implementation supports
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previous versions as non-configured peers; for version-2 configured
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peers a "version 2" keyword should be included on the "peer" line.
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2. The configuration file has a new keyword: statfile <file>, where
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<file> is the name of a statistics file." When present, each clock
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update generates an entry of the form:
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<day> <sec>.<frac> <addr> <status> <offset> <delay> <disp>
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where <day> is the modified Julian day, <sec>.<frac> is the time of
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day, <addr> is the peer address and <status> is the peer status.
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The <offset>, <delay> and <disp> are the measured offset, delay and
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dispersion, respectively, of the peer clock relative to the local
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clock. About once per day the current file is closed and a new one
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created with names <file>.<gen>, where <gen> starts at one and
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increments for each new generation.
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3. A number of additional platforms are supported. See ./Config file
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4. A driver for the TrueTime 468DC GOES Synchronized Clock is
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included. This driver (refclock_goes.c) should also work for other
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TrueTime radio clocks, since all use the same format.
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5. A replacement driver for the Spectracom 8170 WWVB Synchronized
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Clock is included. This driver (refclock_wwvb.c) (a) does not
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require a 1-pulse-per-second signal, (b) supports both format 0
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(original 8170) and format 2 (Netclock/2 and upgraded 8170), (c)
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can be connected to more than one computer and (d) automatically
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compensates for all serial baud rates.
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6. A driver for the German time/frequency station DCF77 is included.
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This requires a special STREAMS module.
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7. In Version 2 special line-discipline modules were required for the
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CHU and WWVB drivers. This code continues to work in Version 3,
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although it is no longer needed for the WWVB driver. However, this
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code does not work under STREAMS, as used in SunOS 4.1.1.
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Equivalent STREAMS modules are supplied with Version 3.
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8. Support for an external 1-pulse-per-second (pps) signal is
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provided. The signal is connected to a serial port (see
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xntpd/ntp_loopfilter.c for details). When present the leading edge
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of the pulse establishes the on-time epoch within an interval
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established by the selected radio clock or other NTP time server.
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Use of the pps is indicated when the tattletale displayed by ntpq
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changes from "*" to "o".
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9. The clock-selection and poll-update procedures have been modified
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slightly in order to achieve better performance on high speed LANs
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with compromise in performance on typical WANs.
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10. In order to comply with U.S. Commerce Department regulations, the DES
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encryption routine lib/authdes.c cannot be exported. For exportable
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versions of this distribution a DES-encrypted version of this routine
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lib/authdes.c.des is included along with an unencrypted version
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lib/authdes.c.export, which allows normal operation, but without the
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NTP authentication feature. Further information is available in the
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lib/authdes.c.export file.
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11. As an alternative to the DES-based authentication mechanism, an
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implementation of the RSA Message Digest 5 algorithm is provided.
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(see applicable copyright information in the library files).
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12. A driver for the Magnavox MX4200 GPS clock.
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13. A STREAMS module which captures carrier-detect data-lead transitions to
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connect a precision source of 1-pps, yet avoid the ugly overhead in the
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usual STREAMS processing. See the ppsclock subdirectory.
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14. Support for the Apple A/UX operating system and enhanced support for the
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Hewlet-Packard HP/UX operating system. See the various README and Config
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files for further information.
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See the COPYRIGHT file for authors and copyright information. Note that some
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modules in this distribution contain copyright information that supersedes
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the copyright information in that file.
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If I missed something or neglected to give due credit, please advise.
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University of Delaware
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31 May 1992, amended 23 July 1992, 25 October 1992
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A bug in the original tty_clk_STREAMS.c module has been fixed.
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The poll-interval randomization feature of poll_update (in
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xntpd/ntp_proto.c) has been extended to apply when the poll interval is
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increased, as well as reduced. This spreads the update messages in time
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and helps avoid unpleasant bursts of messages.
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In the clock_select algorithm the peers selected for combining are
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limited to those survivors at the lowest stratum, not the entire list.
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This helps avoid whiplash when large numbers of peers are at the same
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The number formerly displayed by ntpq as "compliance" is now the time
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constant of integration.
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The DNS resolver xntpd/ntp_intres.c is now integrated into xntpd, making
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configuration of multiple hosts easier.
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System and peer event are now written to the system log at priority
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The leap-second code was fixed to avoid broadcasting leap warnings on
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all except the last day of June and December.