On 14/02/2017 9:23 PM, Chris Albertson wrote:
On Tue, Feb 14, 2017 at 7:31 AM, MLewis <[email protected]> wrote:
- a dedicated machine/box for unencumbered acceptance of PPS, and
- for systems with a business need, a dedicated NTP server/box disciplined
by the PPS source (with dedicated communication), while maintaining
internet NTP sources as backup for when the PPS source fails?
Is there a better way?
Other considerations?
Don't ever think about "backup servers". NTP will always select the "best"
reference clocks. The best ones are defined as the subset of references
that track each other.
Best practice today is to have two independent NTP servers and two GPS
receivers. It is best if these are independent as you can make them,
different buildings if you can. I would even use different brands of
hardware to protect against a bug. Then throughout your company all your
PCs are configured to look at both NTP servers
Each server is configured to use the GPS reference clock, the other "twin"
NTP server as well as about five Internet "pool" servers.
If your location does not have an Internet connection. ( YES this can
happen. I've worked on computers that process classified information and
these computers never have Internet access.) You can configure them so
they run in "orphan mode" that is they all use each other as reference
clocks. Then when GPS is lost thenoormal NTP clock selection algorithm
will select the subset of PCs that all agree on what the time is. The
outliers tent to get ignored. When GPS comes back up the system makes a
gradual and graceful recovery.
Chris Albertson
Redondo Beach, California
That dual set model is new to me. Interesting to see its fall-back on
failures. And the offline model.
It's the poor-man's version of that model that I was aiming for (and
one, not two sets of receiver-with-server):
- A small box as "GPS receiver" with NTP, receiving the PPS from a GPS
timing module.
- That box as a source to an NTP Server that also looks at six internet
pool sources (pools are the 'backup' if GPS/receiver-box fails).
- My systems (two boxes) look to the NTP Server for their time reference.
With all everyone has responded with, as a novice to this I have a lot
of reading to do...
then some choices to make.
Thanks to all
Michael
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