[ntp:questions] does this make sense?

Terje Mathisen terje.mathisen at tmsw.no
Thu Apr 5 06:07:28 UTC 2018

Maria Iano wrote:
> Thanks for your reply, David. Accuracy to within milliseconds is fine
> for us. We currently have four old GPS appliances in four data
> centers that we are replacing, and my thought is that some vendor
> diversity would be good.
> We are only staying in two of those data centers, so that was where I
> was thinking of using GPS as we already have a cable to an antenna to
> the roof. We have a third data center where we currently don't have
> any ntp appliance, and that's where I was thinking it would be
> convenient to put a WWVB device. But we do have access to the roof,
> and from what you say it sounds like we would be better off putting a
> GPS using all three services there.
> We have a network of 12 stratum 2 servers that get time from our
> appliances, and most of our infrastructure points to those, so maybe
> a fourth stratum 1 server is overkill. Does this make more sense:
> three GPS appliances using all three services at the three data
> centers?

I've designed similar setups a couple of times: Since we're located in 
Europe my backup was the German radio transmitter since that one uses 
spread spectrum modulation of the carrier, enabling 10-15 us precision.

With a modern multi-system GNSS receiver and multiple geographical 
locations I would probably be happy with a very good local clock (at 
least TCXO, maybe a second-hand Rb?) to provide holdover and using 
multiple internet sources as a sanity check.


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

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