On Tue, Mar 25, 2014 at 5:52 AM, Paul <tic-...@bodosom.net> wrote: > On Mon, Mar 24, 2014 at 4:26 AM, Poul-Henning Kamp <p...@phk.freebsd.dk >wrote: > >> In message <CABbxVHuQc0144==21mDa_R8ErKov= >> em+9rvrbpggexnzztj...@mail.gmail.com> >> , Chris Albertson writes: >> >> >Yes. NTP calls it "root distance" [...] >> >> And it is generally useless, because people don't calibrate it. >> > > How do you calibrate root distance assuming that it's "one-half the > roundtrip root delay plus the root dispersion plus minor error > contributions not considered here"?
Peole here have very much mis-understood the term "Root Distance". People don't calibrate it because It is NOT a user input. It is an internal variable that NTP uses. It is not something you can input. Perhaps people are confusing NTP's use of this term from the same term used in a different context? "root distance is equal to the root dispersion plus half the root delay" This is a DEFINTION. One does not calibrate a definition. These are measured values done in real-time. It has nothing to do with how one server connects to the others or how many source of time are used. It has noting to do wight eh number of network "hops" or if GPS or an uncalibrated source is used for time. All NTP cares about are the delay in round trip ping time and the variance in those times. I have seen NTP reject a local GPS receiver in favor on an Internet connected pool server because the very old handheld Garmin GPS had such poor timing. This is not uncommon with older nav receivers. Read how it is used here http://www.eecis.udel.edu/~mills/ntp/html/cluster.html Read another definition of "root distance" here: http://www.eecis.udel.edu/~mills/ntp/html/select.html -- Chris Albertson Redondo Beach, California _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.