[ntp:questions] Time sync on a windows domain

Richard B. Gilbert rgilbert88 at comcast.net
Thu May 24 14:30:41 UTC 2007

clarkec8 at hotmail.com wrote:
> Hi,
> I'm investigating different methods of keeping a network in time.  We
> currently have a network with 6000 XP clients, 200 2003 servers and
> about 20 Solaris/Unix servers.
> We currently use ntpdate on the unix servers and w32time on the
> windows server with the PDC going to the internet for time via NTP.
> Our current time difference accross the network is about 2 seconds.
> This seems a lot to me.  We've also go some 2003 servers that swing
> around all over (around 4 mins).  These are pre SP1 though and I
> believe there were some fixes in SP1.
> I would like to get a GPS NTP device and sync to that and I'd like
> some advice.
> 1. If I use the PDC to point to the NTP device and use the domain
> heirarchy what sort of accuracy can I expect?

Good enough for Kerberos which, I believe, means a spread of not more 
than five minutes!  It should usually be better than that but it's not 
guaranteed since Kerberos is the ONLY reason that Windows cares what 
time it is.  See the White Paper by Brandolini and Green entitled "The 
Windows Time Service"  Google for the title and/or authors and you 
should find a copy on the Web somewhere.

> 2. If I still use w32time but set it to NTP and point all clients at
> the clock device what accuracy could I expect?

See above.  Windows was simply not designed for timekeeping. 
Timekeeping, especially accurate timekeeping was very much an afterthought!

> 3. Should I use something else entirely and ignore w32time?

If you really want TIGHT synchronization; e.g. machines all within 35 
milliseconds of each other, then you install and configure ntpd on all 
your machines.  Even this may not be enough since some Windows and Linux 
machines have been known to "lose" clock interrupts when interrupts are 
masked or disabled for too long a time by device drivers.

There are a couple of pre-built ntpd packages for Windows; one of them 
comes with an "installer".

It also helps to have a rock solid time source which usually requires 
something like a GPS Timing Receiver as a reference clock for ntpd on 
the server.


More information about the questions mailing list