leapsecs-boun...@leapsecond.com wrote on 02/17/2009 04:17:20 PM: > On Tue 2009-02-17T20:53:43 +0000, Poul-Henning Kamp hath writ: > > This is a variant of the UUID madness that somebody came up with > > because they didn't want to run a registry or use the existing > > well-structured process (ISO OID's) and though that the eventual > > collisions "probably doesn't matter much". > > And the upshot is software that believes that the system clock is > always right. Or, more weakly, saying the system clock must be > monotonic -- but that is basically saying that if the clock ever gets > fast then it must stay fast. So if the clock gets wrong it must stay > wrong, or else at least it must get right in a fashion that is > consistent with that software's notion -- despite any side effects > that might have on the requirements of other systems that depend on > time.
No, monotonic does not imply that. One can speed up and slow down, so long as one does so gently enough. This is exactly what NTP does in normal operation. > The fallacy that "my sense of time is always right" is what led to a > different kind of collision, the grounding of ships off Scilly in > 1707, and the development of marine chronometers. The navigators who > used marine chonometers knew perfectly well that those chronometers > did not keep the "right" time as measured by clocks on land being > reset by telescopes. Instead they knew that if their chronmeters were > treated well they kept uniform time, and those navigators knew that > getting the "right" time meant keeping a log of the difference between > the "right" time of the clocks on land and their chronometer. They used the best cronometers then available. Harrison's first attempt at a chronometer was in 1730, and success came many years later, in 1760 or so. <http://en.wikipedia.org/wiki/John_Harrison> Joe _______________________________________________ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
