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/contrib/ntp/html/build/hints/notes-xntp-v3

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  1Notes for NTP Version 3
  2
  3This version operates in much the same manner as Version 2 with the
  4following changes and additions:
  5
  61.   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
 142.   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
 283.   A number of additional platforms are supported. See ./Config file
 29     for details.
 30
 314.   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
 355.   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
 426.   A driver for the German time/frequency station DCF77 is included.
 43     This requires a special STREAMS module.
 44
 457.   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
 518.   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
 599.   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
 6310.  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
 7111.  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
 7512.  A driver for the Magnavox MX4200 GPS clock.
 76
 7713.  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
 8114.  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
 85See the COPYRIGHT file for authors and copyright information. Note that some
 86modules in this distribution contain copyright information that supersedes
 87the copyright information in that file.
 88
 89If I missed something or neglected to give due credit, please advise.
 90
 91David L. Mills
 92University of Delaware
 9331 May 1992, amended 23 July 1992, 25 October 1992
 94
 95Bugs and notes
 96
 97A bug in the original tty_clk_STREAMS.c module has been fixed.
 98
 99The poll-interval randomization feature of poll_update (in
100xntpd/ntp_proto.c) has been extended to apply when the poll interval is
101increased, as well as reduced. This spreads the update messages in time
102and helps avoid unpleasant bursts of messages.
103
104In the clock_select algorithm the peers selected for combining are
105limited to those survivors at the lowest stratum, not the entire list.
106This helps avoid whiplash when large numbers of peers are at the same
107stratum.
108
109The number formerly displayed by ntpq as "compliance" is now the time
110constant of integration.
111
112The DNS resolver xntpd/ntp_intres.c is now integrated into xntpd, making
113configuration of multiple hosts easier.
114
115System and peer event are now written to the system log at priority
116LOG_INFO.
117
118The leap-second code was fixed to avoid broadcasting leap warnings on
119all except the last day of June and December.