[ntp:questions] NTP client configuration
david-taylor at blueyonder.co.uk.invalid
Thu Sep 27 14:47:03 UTC 2012
On 27/09/2012 07:08, Benjamin CABUT wrote:
> We are using Meindberg NTP client and server.
> Our configuration is:
> - 1 Computer under windows that is server
> server 127.127.1.0
> broadcast 192.168.2.255 minpoll 4 maxpoll 4 iburst
> disable auth
> - several computer under linux + computers under windows, client of this
> server 192.168.2.250 minpoll 4 maxpoll 4 iburst
> disable auth
> My problem is the following:
> Mainly on windows computer, sometime, depending what the computer is
> doing, there is a big offset between clients and server.
> ("Big" for me is more than 500ms).
> I would like to know if it is possible to setup client so as soon as he
> see offset>500ms, then client do a "fast" synch. (STEP).
> Another way to solve my problem could be for me, to modify the source
> code of my application in order to get this "offset" information inside
> my code (C or C++ langage). then I could add this offset to the time of
> the computer in order to be as much accurate as possible during the time
> the offset is bigger than 500ms.
> Do you have any solution?
> B CABUT
I haven't used "broadcast" or "auth", so I don't know if that affects
things. My understanding of NTP was that unless you configure it
otherwise, an offset exceeding 128 milliseconds would force NTP to step
the PC's clock rather than changing the rate, so I am surprised you are
seeing 500 ms offsets.
I'm using NTP 4.2.7p285 (updated from the Meinberg installation) and
seeing offsets in the millisecond range (except on a couple of PCs where
it's the "few milliseconds" range). This is with three local PCs as
stratum-1 servers, with a GPS reference.
I would not recommend using the "local clock", and if you need an
isolated network I suggest looking into "orphan" mode (about which I
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