Bill, I'm done trying to have a productive discussion with you about this.
H William Unruh writes: > On 2014-12-13, Harlan Stenn <st...@ntp.org> wrote: > > William Unruh writes: > >> On 2014-12-12, Harlan Stenn <st...@ntp.org> wrote: > >> > Mike, > >> > > >> > I think you are seeing the correct and expected behavior. > >> > > >> > The root cause here is that the majority of the upstream servers are > >> > *incorrectly* not advertising the leap second. > >> > > >> > There have been problems before where a misconfigured server has > >> > incorrectly advertised a non-existent leap-second, and in cases where > >> > folks had an adequate number of correctly configured servers, this > >> > mistake was properly ignored. > >> > > >> > I have not been closely following this thread, so I might be missing > >> > something. > >> > > >> > It's pretty easy to download and install a leapsecond file, and ntpd > >> > will pay attention to that... > >> > > >> > Or am I missing something? > >> > >> Yes, That it was an example of a case in which the correct time server > >> could be declared a falseticker. The answer you give "never use sources > >> which might not deliver the correct time" does not obviate the point. > >> The concept of "falseticker" and of "bad time" are not the same thing. > > > > Nobody is saying "never use sources which might not deliver correct time." > > > > Aside from that: > > > > - what is the effective difference between a falseticker and a server > > that provides "bad time"? > > See above. > > > > > - Is this difference really significant? > > See above. > > > > > - If so, how can ntpd determine the difference between a falseticker and > > a server that provides "bad time"? > > It cannot easily. All it can do is decide that something is a falseticker. Bu > t > noone should think, or say, that that means that the falseticker is a > bad time source. It may be the best that ntpd can do. That does not mean > that problems cannot arise precisely because of that. > One could for example simply use all the time sources and use them all. > That has advantages and (as you will be the first to point out) > disadvantages. > > Or you could decide that your own clock is a reasonable flywheel, and > test the outside clocks over time against your won. If you find you own, > while it freewheels, roughly tracks one of the timesources, you have > additional evidence that the one may well be ticking at the right rate. > Yes, this both requires long term memory, and can certainly at times > lead you astray. I am sure I could think of other possibilities as well. > > > > > > > - what real benefits does one get from knowing the difference? > > Clarity in what one is talking about. Care in setting up one's system. > knowledge of what the problems can be. > > Since the purpose of ntpd is to have your computer track the correct > time ( not the majority time) as closely as possible, realising that > there may be difference makes you think differently while developing a > system. What are the costs and benefits of the various possible ways of > trying to disentable the correct time from the various reports delivered > by the servers. > > Maybe majority vote is the best way, but it is certainly not the only > way or even the ideal way in all circumstances. > > I for one would trust time from a gps pps a lot lot more than that from > even 3 other servers. And yes, I could be fooled. Just as you might > trust advice from David Mills much more than any 5 other posters here ( > and would probably be very resistant to a "majority vote" determination > that David is a "falseticker") but that does not give a guarentee that > you could not be led astray sometime. > > > > > > I'm sure a few more questions can come up, but I'm more interested in > > seeing if there might be something useful going on here, other than > > coming up with more issues that NTF's nascent Certification and > > Compliance programs should watch for. > > _______________________________________________ > questions mailing list > questions@lists.ntp.org > http://lists.ntp.org/listinfo/questions > _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
