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Annotation of embedaddon/ntp/html/hints/notes-xntp-v3, revision 1.1

1.1     ! misho       1: Notes for NTP Version 3
        !             2: 
        !             3: This version operates in much the same manner as Version 2 with the
        !             4: following changes and additions:
        !             5: 
        !             6: 1.   The protocol machinery operates in conformance with the RFC1305 NTP
        !             7:      Version 3 specification. The most visible characteristic of this
        !             8:      version is that the poll intervals for all polls, even selected
        !             9:      ones, is significantly increased. This is especially desirable when
        !            10:      serving a large client population. This implementation supports
        !            11:      previous versions as non-configured peers; for version-2 configured
        !            12:      peers a "version 2" keyword should be included on the "peer" line.
        !            13: 
        !            14: 2.   The configuration file has a new keyword: statfile <file>, where
        !            15:      <file> is the name of a statistics file." When present, each clock
        !            16:      update generates an entry of the form:
        !            17: 
        !            18:      <day> <sec>.<frac> <addr> <status> <offset> <delay> <disp>
        !            19: 
        !            20:      where <day> is the modified Julian day, <sec>.<frac> is the time of
        !            21:      day, <addr> is the peer address and <status> is the peer status.
        !            22:      The <offset>, <delay> and <disp> are the measured offset, delay and
        !            23:      dispersion, respectively, of the peer clock relative to the local
        !            24:      clock. About once per day the current file is closed and a new one
        !            25:      created with names <file>.<gen>, where <gen> starts at one and
        !            26:      increments for each new generation.
        !            27: 
        !            28: 3.   A number of additional platforms are supported. See ./Config file
        !            29:      for details.
        !            30: 
        !            31: 4.   A driver for the TrueTime 468DC GOES Synchronized Clock is
        !            32:      included. This driver (refclock_goes.c) should also work for other
        !            33:      TrueTime radio clocks, since all use the same format.
        !            34: 
        !            35: 5.   A replacement driver for the Spectracom 8170 WWVB Synchronized
        !            36:      Clock is included. This driver (refclock_wwvb.c) (a) does not
        !            37:      require a 1-pulse-per-second signal, (b) supports both format 0
        !            38:      (original 8170) and format 2 (Netclock/2 and upgraded 8170), (c)
        !            39:      can be connected to more than one computer and (d) automatically
        !            40:      compensates for all serial baud rates.
        !            41: 
        !            42: 6.   A driver for the German time/frequency station DCF77 is included.
        !            43:      This requires a special STREAMS module.
        !            44: 
        !            45: 7.   In Version 2 special line-discipline modules were required for the
        !            46:      CHU and WWVB drivers. This code continues to work in Version 3,
        !            47:      although it is no longer needed for the WWVB driver. However, this
        !            48:      code does not work under STREAMS, as used in SunOS 4.1.1.
        !            49:      Equivalent STREAMS modules are supplied with Version 3.
        !            50: 
        !            51: 8.   Support for an external 1-pulse-per-second (pps) signal is
        !            52:      provided. The signal is connected to a serial port (see
        !            53:      xntpd/ntp_loopfilter.c for details). When present the leading edge
        !            54:      of the pulse establishes the on-time epoch within an interval
        !            55:      established by the selected radio clock or other NTP time server.
        !            56:      Use of the pps is indicated when the tattletale displayed by ntpq
        !            57:      changes from "*" to "o".
        !            58: 
        !            59: 9.   The clock-selection and poll-update procedures have been modified
        !            60:      slightly in order to achieve better performance on high speed LANs
        !            61:      with compromise in performance on typical WANs.
        !            62: 
        !            63: 10.  In order to comply with U.S. Commerce Department regulations, the DES
        !            64:      encryption routine lib/authdes.c cannot be exported. For exportable
        !            65:      versions of this distribution a DES-encrypted version of this routine
        !            66:      lib/authdes.c.des is included along with an unencrypted version
        !            67:      lib/authdes.c.export, which allows normal operation, but without the
        !            68:      NTP authentication feature. Further information is available in the
        !            69:      lib/authdes.c.export file.
        !            70: 
        !            71: 11.  As an alternative to the DES-based authentication mechanism, an
        !            72:      implementation of the RSA Message Digest 5 algorithm is provided.
        !            73:      (see applicable copyright information in the library files).
        !            74: 
        !            75: 12.  A driver for the Magnavox MX4200 GPS clock.
        !            76: 
        !            77: 13.  A STREAMS module which captures carrier-detect data-lead transitions to
        !            78:      connect a precision source of 1-pps, yet avoid the ugly overhead in the
        !            79:      usual STREAMS processing. See the ppsclock subdirectory.
        !            80: 
        !            81: 14.  Support for the Apple A/UX operating system and enhanced support for the
        !            82:      Hewlet-Packard HP/UX operating system. See the various README and Config
        !            83:      files for further information. 
        !            84: 
        !            85: See the COPYRIGHT file for authors and copyright information. Note that some
        !            86: modules in this distribution contain copyright information that supersedes
        !            87: the copyright information in that file.
        !            88: 
        !            89: If I missed something or neglected to give due credit, please advise.
        !            90: 
        !            91: David L. Mills
        !            92: University of Delaware
        !            93: 31 May 1992, amended 23 July 1992, 25 October 1992
        !            94: 
        !            95: Bugs and notes
        !            96: 
        !            97: A bug in the original tty_clk_STREAMS.c module has been fixed.
        !            98: 
        !            99: The poll-interval randomization feature of poll_update (in
        !           100: xntpd/ntp_proto.c) has been extended to apply when the poll interval is
        !           101: increased, as well as reduced. This spreads the update messages in time
        !           102: and helps avoid unpleasant bursts of messages.
        !           103: 
        !           104: In the clock_select algorithm the peers selected for combining are
        !           105: limited to those survivors at the lowest stratum, not the entire list.
        !           106: This helps avoid whiplash when large numbers of peers are at the same
        !           107: stratum.
        !           108: 
        !           109: The number formerly displayed by ntpq as "compliance" is now the time
        !           110: constant of integration.
        !           111: 
        !           112: The DNS resolver xntpd/ntp_intres.c is now integrated into xntpd, making
        !           113: configuration of multiple hosts easier.
        !           114: 
        !           115: System and peer event are now written to the system log at priority
        !           116: LOG_INFO.
        !           117: 
        !           118: The leap-second code was fixed to avoid broadcasting leap warnings on
        !           119: all except the last day of June and December.