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

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