On Wed, Jul 01, 2015 at 11:39:47AM +0000, Poul-Henning Kamp wrote: > They dropped the raised-cosine thing, because the change of frequency > was bad for the NTP clients PLL's. > > The linear smear is just a slightly different frequency for a fixed > period of time, that's a lot easier for the PLL to track.
A frequency step of ~14 ppm is easier to follow than a gradual change? That doesn't sound right to me, at least not with the standard NTP PLL/FLL loop. I actually have some data from experiments I did when was I implementing a server smear in chrony. Here you can see the offset of ntpd synchronized with a server using a cosine function and a server using a linear function over the same interval. https://mlichvar.fedorapeople.org/tmp/leap/cos_lin_smear.png The maximum offset with the linear smear was almost three times larger than with the cosine smear. I think there is a different reason why they switched to the linear smear. -- Miroslav Lichvar _______________________________________________ LEAPSECS mailing list [email protected] https://pairlist6.pair.net/mailman/listinfo/leapsecs
