unruh wrote: > Of course my 9 machines with drift rates up to -250. It will depend crucially > on which kernel David is running on his linux machines. I suspect is is older > ( one tends not to keep clusters up to date). I used to have distributions > like his. but not for the past two years. > > Anyway 50PPM is not unreasonable. It is also probably unnecessary.
From my (admittedly incomplete) understanding of the algorithms in Das Buch, the key issue is that no server may drift at more than 500PPM in order to maintain the correctness proofs. As noted, this is fudged a bit due to stepping, which appear as arbitrarily large drift rates to a client, but the idea is that if you do it all at once then the damage is mitigated So, this seems to mean that NTP should not be limited to a correction less than 500ppm, but should not serve time until the drift is less than that. Now, as I recall, there is another factor in that the particular implementation of the kernel loop in the kernel reference code only guarantees that there is no overflow when the correction is less than 500ppm. Actually, I seem to recall that it may actually overflow and the largest correction is limited to 500ppm. Brian Utterback _______________________________________________ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions
