[ntp:questions] How should an NTP server fail?

Steve Kostecke kostecke at ntp.org
Fri Jun 11 20:39:13 UTC 2010

On 2010-06-11, Kasper Pedersen <spam at kasperkp.dk> wrote:

> On 06/11/2010 04:47 PM, David L. Mills wrote:
>> My scenario did include the condition of eight valid sample before
>> pulling the plug The first missed poll response did result in one
>> MAXDISPERSE sample in the filter, but that is completely irrelevant.
>> The point is the poll routine calls clock_select() for every poll
>> sent when the last four samples in the reach register are missing, so
>> it is guaranteed that the server be marked down after that.
> For entertainment value, 'ntpq cartoons' with 4 samples, and 8
> samples:
> At 2 minutes after pulling the plug, there is a difference.

I can confirm the observed behavior with 4.2.7p34. However the
inflection point is actually between the 4th and 5th polls.

My experiments this afternoon also showed that the presence or absence of
iburst on the server line has no effect.

Steve Kostecke <kostecke at ntp.org>
NTP Public Services Project - http://support.ntp.org/

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