[ntp:questions] Garmin LVC 18x jitter problem

Miroslav Lichvar mlichvar at redhat.com
Thu Aug 15 07:38:09 UTC 2019


On 2019-08-14, Michael Haardt <michael at moria.de> wrote:
> keyid=0, ttl=0, offset=-21.688, delay=0.000, dispersion=199.450,
> jitter=7.766,
> filtdelay=     0.00    0.00    0.00    0.00    0.00    0.00    0.00    0.00,
> filtoffset=  -21.69  -24.50  -21.05  -20.86  -24.06  -31.32  -18.34  -39.11,
> filtdisp=    200.00  200.24  200.48  200.72  200.96  201.20  201.44  201.68
>
> Indeed I used minjitter 0.2.
>
> I can't say that I understand the difference, though.  Do I modify what
> I should modify?

I think you do. To prevent the source from being rejected as a
falseticker it needs to have a larger root distance. That could be from
a larger dispersion or delay. You modified the refclock jitter, which
ends up in the peer dispersion (after some weighting). Another approach
would be to specify a minimum for the peer dispersion directly. There
could be also an option to specify a minimum delay. But adjusting it in
the refclock specific code, as you did, makes perfect sense to me.

-- 
Miroslav Lichvar



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