[ntp:questions] Is it possible to confuse ntpd's freq error measurement procedure?

Paul Malishev p.malishev at gmail.com
Thu Jun 7 10:23:57 UTC 2012


Oh. Thanks.

This "true" flag may be the root cause of the problem. Along with slew
adjusting instead of stepping. Thank you, I'll try to investigate his
problem further.

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> Paul Malishev wrote:
> > I have two ntpd peers which exchange time between
> >  themselves and also receive time from external server.
> > I believe that at some moment connection to external
> >  server was lost and time on these two peers drifted a bit.
> >
> > When connection to external server was restored both ntpd
> >  on both peers logged something like:
> > Jun  5 13:21:09 peer0 ntpd[5052]:
> >  frequency error 18158 PPM exceeds tolerance 500 PPM
> >
> > After that there were a lot of messages with not so big freq error:
> > Jun  5 13:23:18 DIG ntpd[5052]:
> >  frequency error 608 PPM exceeds tolerance 500 PPM
> ...
> > When an operator saw time difference with external server about 30sec
> ...
>
>  They must have been unable to reach the external server,
>  for a really long time?
>
>
> > server 127.127.1.0 noselect
> > fudge  127.127.1.0 stratum 10
>
>
>  If it looses the all other servers, it will likely continue
>   to run away at whatever frequency was last set;
>  If it can still contact the internal peer,
>   they should run off together (or one would chase the other).
>
>  You might try orphan mode instead; e.g.
>
> tos cohort 1 orphan 10
>
>  <http://www.eecis.udel.edu/~mills/ntp/html/orphan.html>
>  {Although I'm not certain it would have any significant value,
>    when only one other server can be reached.}
>
>
> > restrict 192.168.0.240 mask 255.255.255.240
>
>  If you ever use a server by host name,
>  especially when the name may return multiple A records,
>  (e.g. pool servers) you may need to add a restrict source
>  line; e.g.
>
> restrict source nomodify
>
>
> > tinker step 0
>
>  Remove that if you want it to step, instead of slew always.
>  BTW, step 0 also disables kernel discipline!
>
>
> > tos minclock 1 minsane 1
>
> MinSane defaults to 1 ?
>
>
> > peer 192.168.0.241 burst iburst minpoll 4 maxpoll 6 prefer true
> > server **external-server-ip** burst iburst minpoll 4 maxpoll 6 true
>
>  You should not do "burst" on servers that are not your own.
>  {I have no idea who **external-server-ip** belongs to.}
>   {"iburst" is fine}
>
>  The docs also seem to say to not use burst or iburst with "peer" ?
>  <http://www.eecis.udel.edu/~mills/ntp/html/assoc.html>
>  <http://www.eecis.udel.edu/~mills/ntp/html/confopt.html>
>
>
>  Are you really intentionally saying to treat both
>  the other internal server and the external server
>  as if they always have valid time, with the true option?
>   {Even if some day they may not be even close.}
>
>   Are you treating them both as true chimers
>    because you only have two servers to reference?
>
>
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