[geeks] NTP on Windows

[Dan Sikorski]

On 6/21/2011 8:40 AM, gsm at mendelson.com wrote:
> On Tue, Jun 21, 2011 at 08:18:06AM -0400, Nick B wrote:
>> Windows XP has ntp built in.  Are these networked with any remote 
>> agents?
>
> No it does not. At least not in the sense that anyone who uses NTP would
> think it does. Once a week it checks your clock against a server and 
> updates
> it.
> A "real" NTP client would keep your clock in sync. About 200ms (1/5 of
> a second) is what's needed for software development, otherwise make
> (and similar programs) might not get things straight.

If it is an active directory domain member this behavior is changed.  A 
domain member will sync with it's domain controller more frequently.  
That said, Microsoft documentation (which I am too lazy to find at the 
moment) states that this client is not for transactions that are 
sensitive to the millisecond and in extreme cases can allow drift up to 
a couple of seconds across a large domain, but my experience in smaller 
domains has shown that it is much more accurate than that.  Clients and 
member servers sync to their domain controller, and the domain 
controllers sync to the one that has the PDC Emulator FSMO role.  If the 
machines in question are domain members, this should keep your clocks 
accurate unless you need sub .2 second accuracy.  It primarily exists to 
ensure proper kerberos operation.  I assume that the machines in 
question are not domain members or this solution is not acceptable for 
some reason, so this is irrelevant, but thought that it bears 
mentioning.  If they are domain members and you add a third party NTP 
client, be sure that it is on all machines in the domain and the native 
one is disabled or you may have odd behavior.

     -Dan Sikorski