[ntp:questions] Garmin 18 LVC: whether to fudge
Hans Jørgen Jakobsen
hjj at wheel.dk
Sun Feb 15 22:44:08 UTC 2009
On Sun, 15 Feb 2009 18:04:36 GMT, Unruh wrote:
> Hans =?iso-8859-1?Q?J=F8rgen?= Jakobsen <hjj at wheel.dk> writes:
>
>>For my 14M/1.5M VDSL line I see an offset of 7-800 microseconds:
>> ntpq -p
>> remote refid st t when poll reach delay offset jitter
>>==============================================================================
>>-ns.tele.dk .GPS. 1 u 48 64 377 22.450 0.891 0.096
>>-tix.ns.tele.dk .GPS. 1 u 7 64 377 22.338 0.698 0.183
>>-puma.tele.dk .GPS. 1 u 19 64 377 27.048 0.784 0.145
>>+GPS_HP(0) .GPS. 0 l 10 16 377 0.000 -0.776 6.230
>>oPPS(0) .1PPS. 0 l 10 16 377 0.000 0.012 0.015
>>+GPS_ONCORE(0) .GPS. 0 l 8 16 377 0.000 0.035 0.006
>
> Something is really weird here. .776ms from a GPS refclock is horrible.
> That is about a factor of 300 worse than you would expect. In fact all of
> your GPS refclocks show bad time What are you doing to your clocks?
>
Dave Hart has given the answer why they behave as they do.
>
>>20.6 ms of the roundtrip time are spend on the DSL line.
>
> How do you know it is exactly 20.6ms?
>
I left out that I have acces to above ntpservers and have done a ping to the
DSLAM. Ping ns.tele.dk <-> DSLAM are ~1.85ms. Symmetric delay can be assummed.
/hjj
More information about the questions
mailing list