On 2019-07-31, Andrew Harrison <aharri...@gmail.com> 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 think that the problem is that if ntpd gets invalid packets, it simply ignores them (as it should because missing a few packets is standard behaviour) It simply free runs on the last good packets to come in, since it has nothing else to go by. Apparently it is not actually using the second device while the first is working ( and besides, it would have a hard time deciding which was good and which not). Have you tried using both of the symmetricons as sources always. Then there is a change that if one goes offline, the other one will automatically get picked as the source? Or perhaps you could query the machines, or the symmetricons, to see if they have gone nuts (invalid stratum) and then have that program do the substituting for you (by sending ntpd a change of source)? Ie, you have a second program being the scount to see whether the data coming in is OK. > > 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! > > _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
