[ntp:questions] high precision tracking: trying to understand sudden jumps
Richard B. Gilbert
rgilbert88 at comcast.net
Mon Mar 31 19:16:14 UTC 2008
David Woolley wrote:
> Heiko Gerstung wrote:
>> time has passed without the signal coming back. This results in the
>> time server replying with stratum 12 (for example) after a while and
>> ensures that everybody has the same time, although it might be wrong.
>> If a user does not want that, they can simply set the local clock
>> stratum to 15 and the server will not be accepted anymore.
>> Can you please let me know why you consider this a "bad implementation"?
> Because the protocol fails to signal the loss of the time source
> properly when one has a local clock configured. As such, I believe that
> enabling a local clock should always be an opt in choice. Basically,
> when it falls back to the local clock, root dispersion goes to zero,
> when the true situation is that root dispersion is growing without bound.
> Things can go seriously wrong if there is more than one local clock
> source on a network, as it becomes possible for them to outvote the real
Local clock IS an opt in choice. If you don't configure it, it doesn't
serve time. Stratum is taken into account in selecting a time source.
I can't swear to it but I'd be surprised if three stratum 10 servers
could out vote one stratum 2 server.
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