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

blu brian.utterback at gmail.com
Wed Jun 9 19:53:20 UTC 2010

On Jun 5, 4:11 pm, David Mills <mi... at udel.edu> wrote:
> goofyzig,
> This issue is widely misunderstood; yours is the second such message to
> me today. So, please spread the word.
> When a server loses all sources it does not necessarily become
> unsuitable for downstream clients. Ordinarily, it inherits error
> statistics from upstream servers and provides them to downstream
> clients. Servers and clients use these statistics to calculate the
> maximum error statistic which represents the maximum clock error
> relative to the primary reference clock. See the error budget called out
> in the specification. Once determined, the maximum error increases at a
> rate (15 PPM) determined as the maximum disciplined clock frequency
> error of the server clock. This increase continues indefinitely or until
> the sources are again found.

Since you have requested that this be discussed on the newgroup rather
than in bug 1554, I am replying here.

In bug 1554, the reporter claims that what you describe above is what
he sees happen if the clock filter contains 4 to 7 samples. However,
he says that if the clock filter is full with 8 samples, then the
system peer is unselected and a no_sys_peer event is posted. This is
in contradiction of what you keep describing as the correct behavior,
but then you keep saying that the reported behavior is correct. Since
the behavior he is reporting is not the same correct behavior as you
keep describing it, we have continued to treat this as a bug.

So, you need to either confirm that this change in behavior at 8
samples is correct and amend your description,  or confirm that your
description is correct and admit that the reported behavior is a bug.
Or deny the reported behavior happens (I tend to favor this at this
point. I suspect user error right now.) In either of these last two
cases, we should probably still discuss this in the bug report.

Brian Utterback

More information about the questions mailing list