[ntp:questions] symmetricom tp1100 stratum and leap indicator behavior

Terje Mathisen terje.mathisen at tmsw.no
Fri Aug 2 12:56:00 UTC 2019

Andrew Harrison wrote:
> On Thursday, August 1, 2019 at 7:43:32 AM UTC-4, Terje Mathisen
> wrote:
>> I ran the ntp setup for Norway's largest multinational corporation
>> for 20+ years, my final setup used dedicated
>> TrueTime/Symmetricom/Meinberg gps-based servers in 3 main
>> locations, augmented with radio-based clocks in a couple more as
>> well as several hand-made FreeBSD servers using Oncore and SURE
>> evaluation boards with timing gps receivers.
>> All these primary sources were used as references for a second
>> layer of dedicated Stratum 2 servers, two in each of those 3 main
>> geographical centers, and with identical/symmetrical conf files.
>> The latter works because an ntpd server automatically omits any
>> circular reference, to itself or another source.
>> Finally, every single client machine capable of running the full
>> ntpd stack was configured to use all 6 Stratum 2 servers as their
>> reference, this provided enough redundancy that we never suffered
>> any visible hickups even when we passed through the GPS week
>> rollover or when an individual reference server lost a leap second
>> event.
>> Except for the hardware ref servers, this was all effectively close
>> to zero cost, only some labor hours.
> Sounds similar to what my eventual plan is, once I get this working.
> The Symmetricoms will be accessed by only two servers running ntpd.
> All other devices will pull time from those two servers, they won't
> talk to the Symmetricoms directly.
> I just need to figure out how to get ntpd to notice and behave
> appropriately when the Symmetricom stops advertising itself as
> stratum 1.

I suspect your "prefer" option (which I think you reported using?) might 
be the culprit? Have you tried your setup without any indications of 
which serer(s) to prioritize?

> We now have a support contact with Syncworks and one of their guys
> has been trying to figure this out with me as well, including him
> reaching out to some of his contacts at MicroSemi.  No luck so far,
> but it isn't looking good since this is starting to feel more like a
> bug in ntpd.

What happens to the dispersion figure when you remove the antenna?

If you have logging configured then you should be able to see how this 
is handled: YOur client machines should notice that the other server has 
much higher quality even if the stratum level is the same (and even if 
this is really a bug).
> Frustrating, since this will probably all be moot next year.  I have
> to get another year out of our Symmetricoms before we can buy new
> ones that aren't well beyond EOL.
Good luck!


- <Terje.Mathisen at tmsw.no>
"almost all programming can be viewed as an exercise in caching"

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