Dave, Somehow using an HP 5071 to discipline the time without kernel support seems bizarre, but it could be done in a spacecraft with only intermittent contact with Earth. At the default rate of dispersion increase of 15 us/s and distance threshold at the default 1.5 s, the client will coast about 2.8 h. The tos maxdist 5 command would increase that to 3.9 h. The downside to this is that this also reduces the number of measurements when first synchronizing. Note that the kernel has no distance threshold, so in principle could go forever without a prefer peer.
The distance metric is intended as a maximum error statistic and includes components due to roundtrip delay, dispersion, absolute offset and RMS jitter. It was never intended for use as a holdover for absentee prefer peers. There are other ways to do this, all with unintended side effects. A related problem has occured with simulated Moon missions, in which the roundtrip light time is over 2 s. An increase in distance threshold to 3 s fixes this, but something else is necessary for missions beyond the Moon. Dave Dave Hart wrote: >Dr. Mills, > >Thank you for your confirmation. The original poster should be >satisfied, assuming their kernel time is being disciplined directly by >their cesium standard. If they are unable to use the kernel >discipline for some reason, could they tinker _max_disp (I don't know) >to keep the upstream server with GPS surviving longer? If there is no >maximum dispersion tinker, "tinker dispersion 5" on the upstream >server with GPS should similarly delay the inevitable. (The default >is 15, units part per million) > >Cheers, >Dave Hart > > >On Mar 23, 3:22 am, mi...@udel.edu (David Mills) wrote: > > >>Dave, >> >>Once the kernel PPS is lit, it will stay lit even if the daemon loses >>the prefered soure or even dies.This is the intended behavior, which I >>confirmed just now. Veriy that ntptime shows PPSTIME lit after the >>daemon loses the prefer peer or is stopped. >> >>By the way, with just a remote peer and PPS, the intersection algorithm >>is quite picky if the remote peer strays a bit. Use tinker mindisp to >>something higher, like .05 s. >> >> > >_______________________________________________ >questions mailing list >questions@lists.ntp.org >https://lists.ntp.org/mailman/listinfo/questions > > _______________________________________________ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions
