[ntp:questions] Time offset / Jitter under FreeBSD

Garrett Wollman wollman at bimajority.org
Sun Dec 2 17:52:27 UTC 2007


In article <fitlnh$phn$1 at registered.motzarella.org>,
Bob <bobsjunkmail at bellsouth.net> wrote:

>I installed FreeBSD on a drive, and booted my windows machine from it. The 
>FreeBSD port of ntpd shows a offsets in the 20-60 ms range. Issues with 
>jitter, also.

How long did you leave it running?  What drift value was reported?

My stratum-0, running FreeBSD 6.2, consistently reports offsets to
other stratum-0s within +/- 5 ms, and to its refclock within a couple
of microseconds with the nanokernel and kernel PPS.  My stratum-1s,
likewise.  These are all running the stock ntpd, which is 4.2.0-a.

$ ntpdc -c kerni ntp-0
pll offset:           1.314e-06 s
pll frequency:        68.119 ppm
maximum error:        0.012947 s
estimated error:      7e-06 s
status:               2107  pll ppsfreq ppstime ppssignal nano
pll time constant:    6
precision:            1e-09 s
frequency tolerance:  496 ppm
pps frequency:        68.119 ppm
pps stability:        0.022 ppm
pps jitter:           1.142e-06 s
calibration interval: 256 s
calibration cycles:   85694
jitter exceeded:      506860
stability exceeded:   0
calibration errors:   3

(The refclock here is an EndRun Technologies Praecis Ct.)

-GAWollman
-- 
Garrett A. Wollman   | The real tragedy of human existence is not that we are
wollman at csail.mit.edu| nasty by nature, but that a cruel structural asymmetry
Opinions not those   | grants to rare events of meanness such power to shape
of MIT or CSAIL.     | our history. - S.J. Gould, Ten Thousand Acts of Kindness




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