[ntp:questions] NTP under AIX?

William Unruh unruh at invalid.ca
Wed May 17 05:14:08 UTC 2017

On 2017-05-16, Greg Moeller <skywise at gmail.com> wrote:
> On Tuesday, May 16, 2017 at 3:36:07 PM UTC-5, William Unruh wrote:
>> Yes. But again it depends on its time source. Using a gps receiver with
>> a PPS output will give time to a few microseconds of UTC. If you are
>> serious about time for your systems, get a gps. You can run a coax out
>> to a window somewhere where you put the gps antenna. A hundred feet of
>> coax should get you out to window-- preferably facing south with a
>> realtively clear viewof the sky.  If needed you can
>> compensate for the time delay along that cable ( about 1.5ns per foot if
>> you require that accuracy-- you still have not told us what accuracy
>> you want. ).
> That would imply there are windows.  This is one of those places with trapping passages in case intruders try to storm the datacenter, windows would be a fatal weakness.  :)

There are no windows anywhere in the building? Then mount it outside on
the wall:-) Ie, I did not assume there were windows inside the
datacenter but somewhere on the same floor as the datacenter that you
could run a line to. 

>> Re your people-- don't call it a computer. Call it an ntp time source.
>> Make a nice box for it if nessary and still come in well under the spare
>> change limit in your organization.
>> But yes, a nice oven controlled crystal dedicated system would serve
>> time best. You can buy them. Of course the time that the computers in
>> your organization got from it would be much less accurate, and probably
>> no worse than if youuse an RPi with a Sure GPS receiver (about $80-- 100
>> with box).
> I'm looking at simple stable time.  Time used to come from AD servers keeping their own time.  Standing there with a pocket watch would be an improvement over that.

Simple stable time does not really mean much. What accuracy do you want?
Seconds, msec, usec, nsec? All have different solutions.

> Currently, we have 3 DMZ servers getting time from the internet (stratum 2 and 1), then 2 NTP servers inside the DMZ getting time from those 3 servers.  The inner environment then gets time from those two. (AD also gets it's time from the 3 DMZ servers, putting them on equal footing, stratum-wise)

So the DMZ has a tunnel under it-- the connection of the inside to the
outside ntp.
An since the outside ones all serve all the inside ones, that hole is
really wide open. Exactly what is the purpose of this DMZ?
One or two cables o gps receivers outside, which are pretty hrd to
subvert, would seem to be safer than this.

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