[ntp:questions] Client doesn't drop failed source

David Woolley david at ex.djwhome.demon.invalid
Sat Jan 9 09:31:34 UTC 2010

Richard B. Gilbert wrote:
> Michael Moroney wrote:
>> David Woolley <david at ex.djwhome.demon.invalid> writes:
>>> Michael Moroney wrote:
>>>> that synchronizes with the four clocks, and ntpq> peers shows one of 
>>>> the
>>>> primaries with a "*" in the first column meaning it was synchronized 
>>>> to as
>>>> time source, the other 3 show "+" as expected, meaning they are usable
>>>> sources.  We disconnect the antenna of the selected clock.  As expected
>>> * and + mean they are used, not just that they are usable.  The time 
>>> used to discipline the clock is a weighted average of all of them.
>> If it uses all of them, what is the difference between "*" and "+"?
>> It still doesn't explain why the disconnected clock doesn't get dropped.
> "*" designates the primary source of time.  "+" designates an "advisory" 
> source.  It's available for use if something happens to the primary source.

You are making the same mistake that he was making.  * means the source 
of time used to determine the stratum, and downstream root distance and 
dispersion.  + and * both mean that the time is being used to discipline 
the local clock.  + is not a standby, as far as disciplining the clock 
is concerned; + entries are actively used to discipline the clock.

On V3, the time used to discipline the local clock is a weighted average 
based on a quality metric - I forget exactly which one.  I'm not so sure 
that V4 applies as much weighting.

More information about the questions mailing list