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

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Thu Jun 7 01:29:04 UTC 2012

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 noselect
> fudge 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

  {Although I'm not certain it would have any significant value,
    when only one other server can be reached.}

> restrict mask

 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 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" ?

 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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