[ntp:questions] How is the NTP build tested?

Jochen Bern Jochen.Bern at LINworks.de
Wed Jan 15 20:10:50 UTC 2014


On 14.01.2014 18:53, William Unruh wrote:
> On 2014-01-14, Terje Mathisen <terje.mathisen at tmsw.no> wrote:
>> The entire NTP ensemble, from the current machine and up to all its 
>> sources, constitute a distributed control loop, right?
>>
>> This means that the stability and eventual precision of any given clock 
>> depends upon exactly how all the source (server/peer) clocks behave, it 
>> is easy to come up with scenarios that will become unstable and lead to 
>> oscillating clocks.
> 
> Well, no. It is precisely to stop feedback loops that the whole issue of
> stratum was set up. A stratum x system cannot use a stratum y>x as a
> source or it becomes a stratum y+1 system. Without feedback you are not
> going to get instability. If this were possible, it would be a problem
> even with the ntpd algorithm.

Sorry, no. It's perfectly possible for an ntpd to cycle its sync source
through several different-strata servers, rather *common* even if you're
using 127.127.1.0 for a high-stratum one AFAICT. That's a huge delay
buffer in the feedback loop through your peered systems, sure, but a
loop it still can be(come).

Kind regards,
								J. Bern
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