[ntp:questions] Re: Problem with good synchronization.

Danny Mayer mayer at gis.net
Sat Oct 16 21:44:32 UTC 2004

Marcin Okraszewszki <okrasz_news at o2.pl> wrote in message news:<mailman.24.1097844932.72027.questions at lists.ntp.isc.org>...
> Hi,
> I need to synchronize computers' clocks very tightly. I mean clocks
> offset shouldn't exceed 50ms. All computers are in the same LAN, so in
> fact network traversal time isn't very big. But with default settings I
> find that offset even goes to 700ms, and from time to time there are
> some step clock changes that are highly undesirable (at least with
> amount of 500ms).
> I tried to set minpoll 4 and maxpoll 5 turned step 0 (to avoid sudden
> time changes) The results are as fallows: absolute value of offset has
> reduced to average 70ms with standard deviation 90ms and maximum 350ms.
> This is not good enough. What is even worse, suddenly the time offset to
> server was 60s (not ms)!! And it happened in all clients at the same
> time, which for me means that something happened with the time on the
> server, but there is nothing about it in the system log.
> Is there any way to improve this situation?
> The ntp server is running Windows 2000 (ntpd 4.1.72) and clients are
> Linuxes (ntpd 4.1.1). To measure the offset I use ntptrace. The Windows
> is not synchronized to any other source.
Please upgrade to 4.2.0a for all of these machines. If you don't have
any external source or clock on the windows machine, you are subject
to the mercy of the vagaries of the operating system, interrupts, etc.
If accuracy like this is that important to you should should invest money
in a clock module or at least have it use some of the stratum 2 servers
available over the Internet. Nothing else will give you the kind of
accuracy you say you need.


> Thanks for help.
> Marcin Okraszewski

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