[ntp:questions] Synchronization and Non-Synchronization status

Jaiprabhu jaiprabhu at somewhere.in.this.world
Sat Feb 20 20:01:24 UTC 2010

David Woolley wrote:
> Jaiprabhu wrote:
>> I have observed that the server reaches the reject state, while the 
>> stratum stays the same (it was at 1), a long time after it moved into 
>> the reject state. The server was moved to the reject state by making 
>> it unreachable by adding it's IP in an iptables drop rule. The reject 
>> state already means that the server is not a synchronization source. 
>> What's the rule of thumb on the duration it would take for the stratum 
>> shifting to 16?
> It should shift when the last available sample is too old to really 
> correlate well with the true time.  There is a definite drop dead when 
> the root dispersion reaches about a second.  I thought that the stratum 
> collapses when somewhere between about 4 and 6 polls have been lost, but 
> it might not be until the estimated error (root dispersion) becomes too 
> large.

On my x86, running Ubuntu 9.04 and ntpd 4.2.4p4, it did not collapse 
even after losing the 6th poll. I did not track the root dispersion but 
I was tracking the time elapsed after all the configured hosts were made 
unreachable for a while, and, it did not drop to stratum 16 till at 
least 30 minutes after. I stopped keeping track after that.

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