> -----Original Message----- > From: questions- > [email protected] > [mailto:questions- > [email protected]] On > Behalf Of David Woolley > Sent: Saturday, December 22, 2012 6:14 PM > To: [email protected] > Subject: Re: [ntp:questions] FW: Clock Offset > > unruh wrote: > > On 2012-12-22, Mischanko, Edward T > <[email protected]> wrote: > > >> I do not doubt you, but if they are measuring different > things > >> to represent the same thing, then there is a formula off > >> somewhere? > > > > No, they do not "represent the same thing". They are different > things. > > One is the instantaneously measured offset between the local > clock and > > the servers. The other is the best estimate ntpd has for the > difference > > between the local clock and true UTC time. > > I don't believe he is now comparing the overall estimate with > the most > recent individual measurements. I think he is comparing the > best > estimate for an individual source, with the ntpq peers, most > recent > offset for that source. > > The formula for an individual filtered offset is something like: > > (z ^ n) * Offset > > where z is the Z-Transform operator and n is an natural number > <= 7, > such that (z ^ n) * estimated-offset-error is minimal. Of > course, it > is not described that way in the actual code, and I don't think > it is > described that way in the documentation. > > I believe the error estimate includes the round trip delay, and > the > stratum, but it is that sort of thing that is subject to change. > > _______________________________________________ > questions mailing list > [email protected] > http://lists.ntp.org/listinfo/questions [Mischanko, Edward T]
David, Thank you for your time in explaining this to me. Unfortunately, my mathematics education stopped at intermediate algebra; it appears that the formula is in calculus? Anyway, I feel like I have beaten this horse to death. I can accept the fact that they are different and yet notice their similarities. I'm not sure Unruh completely understands my point? Regards, Ed _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
