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

Chris xxx.syseng.yyy at gfsys.co.uk
Wed Jul 31 23:23:50 UTC 2019


On 07/31/19 20:10, Andrew Harrison wrote:
> The backstory...  I've been tasked with deploying a pair of Symmetricom TP1100 Time Providers with GPS antennae as the official time source for the company (replacing an ancient server with a Meinberg card in it).  My company actually purchased the Symmetricoms a few years ago, but they never got around to putting them in production.  No one was able or willing to put in the time to get them going.  I started working at the company recently and they gave the project to me.
>
> I've got them up and running and my test ntp client (my Linux workstation running ntp 4.2.8p12) can pull time from them just fine.
>
> Now for the hard part.  What we want to happen is that if the GPS of the primary Symmetricom goes offline, we want the clients to start getting time from the backup unit.
>
> Ideally what would happen is the GPS goes offline, the Symmetricom would set itself to a higher stratum level and the clients abandon it for the device that has the better stratum, but this is not what happens.
>
> I had to use Wireshark to see that instead, when the GPS goes offline, the Symmetricom stops advertising a stratum level (Wireshark shows "unspecified or invalid") while the leap indicator shows "clock unsynchronized" (3 I think it was).  (When I enable the GPS again, Wireshark shows the stratum level coming through as 1 and leap indicator shows 0 "no warning".)
>
> On my workstation test client, ntp apparently doesn't know what to do when a time source stops indicating its stratum level so it keeps right on showing stratum 1 in ntpq output even though Wireshark clearly shows the packets coming through with stratum level "unspecified or invalid".
>
> So, my question is, can I configure ntp in such a way that it responds to either a lack of advertised stratum or a leap warning indicator greater than 0?
>
>
> Thanks!
>
>


If you have 2 servers, both gps, then the polling host needs to
have config to allow fallback to the second unit when it fails.
Not a time server issue afaics, unless each has fallback ability in
itself.

What you could do is run ntpd on a third host, polling both time
servers along with a host or two from an ntp pool, which should have
the ability to spot the outlier and continue providing accurate time.
Not sure about the overall behavior, but wouldn't take long to set
it up and check results...

Chris



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