David,
I have no idea whatsoever what you are talking about. If you need to
test whether the clock state machine correctly responds to large time
offsets, then my suggested scheme is exactly what you need. I have
tested every NTP version since 1982 in just that way, most recently to
confirm the clock is set correctly after the 2036 roll.
Using a large time step offset is not the way to test the PLL/FLL
functionality, and I did not intend the "classic" scheme to test it thar
way. The PLL/FLL loop is pseudo-linear and needs to be perturbed by a
small offset less than the step threshold (128 ms). Either that or
change the step threshold to something large and set the offset manually.
I test by setting the frequency to something large, like 500 PPM and
running the daemon (or kernel) for a few minutes in order to accumulate
a modest error, like 100 ms. Then, restore the original frequency file
or delete it, as required and restart the daemon. The intent is to
confirm the zero crossing as the loop converges (about one hour) and to
confirm the overshoot is modest (less than 6 percent). All this with a
64-s poll interval.
Your last comment is confusing. I have never criticized folks for doing
tests involving step or linear adjustments. What I have done is question
the wisdom of forcing the step threshold to very large values in order
to insure monotonic adjustments. The reasons for this are explained in
the white papers at the NTP project site.
Dave
David Woolley wrote:
In article <[EMAIL PROTECTED]>,
David L. Mills <[EMAIL PROTECTED]> wrote:
Classic way to test NTP functionality is to stop ntpd, set the time by
This isn't a classic way because it hasn't been an available option for
long enough. It's also not classic because it is not what people actually
do; what they actually do is to change the time on a running client (or,
if they are using an undisciplined local clock on the server, change the
time on a running server).
As I pointed out, it is also not a valid test because it fails to demonstrate
the phase locked loop in ntpd, which is the main part of ntpd, except in as
much that someone more knowldedgeable than the sort of person for which this
sort of demonstration is done, may be able to see the final convergence onto
the correct time and frequency.
If you really think it is a good test, I'm surprised that you have let so
many regulars here criticise people for doing these step change tests in the
past.
some other means within 68 years of the correct time, then start ntpd
with -g.
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