[ntp:questions] GPS driver failure mode question

Charles Brown charles.brown at sensis.com
Mon Jan 12 22:57:55 UTC 2009


    I linked from the LCL driver to the Orphan Mode documentation, and 
this seems to be the answer to my original (poor) question.

    Three questions on orphan mode;

    First, the orphan mode page says;

"Each orphan child chooses the orphan parent as the root server with the 
smallest value."

Which value is that? Stratum?

    Second question, using the diagram from the orphan mode section; 
Suppose all sources go away, orphan mode kicks in and all the children 
and Server B select Server A as the orphan parent.  Subsequently, Server 
A dies. Will Server B take on the parent role, and all children respond 
appropriately?

    Third question; Suppose A gets well, still without its external 
sources, and comes back. Will Server B defer being parent back to server 
A, so Server A becomes parent again, and Server B and all the children 
respond appropriately?

--CB

Terje Mathisen wrote:
> Unruh wrote:
>  > Steve Kostecke <kostecke at ntp.org> writes:
>  >> Never.
>  >
>  >> The Undisciplined Clock Driver does poll the system clock
>  >> (often misleadingly referred to as the "local clock") _but_ the poll
>  >> results are discarded. So ntpd never actually serves time _from_ the
>  >> Undisciplined Local Clock.
>  >
>  >
>  > Sorry there is some sematic distinction going on here that I do not 
> follow.
>  > ntp always "serves time" from the system clock. The question is how and
>  > whether ntp thinks that system clock itself is being disciplined. If 
> it is
>  > disciplined by nothing it does not act as a server, and says so. If it is
> 
> It can still do so, but definitely not by default!
> 
>  > "disciplined " by local clock, it is still disciplined by nothing, 
> but can
>  > act as an ntp server, and tells outside clients that it is being
>  > disciplined by the local clock. Am I wrong in my understanding?
> 
> Slightly, see the documentation page for the local clock driver:
> 
> http://www.eecis.udel.edu/~mills/ntp/html/drivers/driver1.html
> 
> Terje
> 
> --
> - <Terje.Mathisen at hda.hydro.com>
> "almost all programming can be viewed as an exercise in caching"
> 
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