[ntp:questions] symmetricom tp1100 stratum and leap indicator behavior
mike.cook at orange.fr
Thu Aug 1 05:51:51 UTC 2019
> Le 1 août 2019 à 01:23, Chris <xxx.syseng.yyy at gfsys.co.uk> a écrit :
> 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?
If a server is reporting the stratum level « unspecified or invalid » the client will not use it in synchronizing. IIRC it will eventually show up as stratum 16. I think that the reason you are still seeing stratum 1 in your client ntpq output is that the client has not had enough time to figure out whether the server is really dead , or it was a glitch. This can take some time. Anyway, do not worry as the client network will not use it. There are no configuration options to change the client status instantaneously.
> 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
> 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...
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