[time-nuts] NTP for 64 bit windows

Anthony G. Atkielski anthony at atkielski.com
Tue Jan 17 08:44:32 EST 2012

> 1) Does windows really implement NTP? I thought it was SNTP.

Apparently, in current versions of Windows, it is a home-cooked
version of an NTP client. All I know is that my PC stays accurate
within a very small fraction of a second while synchronizing from my
NTP server (the UNIX machine sitting next to the Windows machine on my
LAN), and I'm not using anything other than the standard Windows
built-in client. About the only parameter I've adjusted has been the
synchronization interval: by default, it's set to a week, and I've set
it to seven minutes (synchronization costs nothing between two machines
on a LAN).

I used to use a payware synchronization client, but when I discovered
that the built-in client was just fine as long as the polling interval
was short enough, I stopped using the payware. The main problem with
the built-in client just seems to be that it waits so long between
synchronizations: days, in other words, whereas the average PC is off
by several seconds each day if not constantly corrected.

It's possible to improve the accuracy of system time enormously just
by shortening the interval to once or twice a day, depending on how
much accuracy you want or need.

> 2) PC hardware running Linux/xBSD and the NTP reference
> implementation, runs very well att polling rates of 1024 seconds or
> longer. (Keeping sub 1ms accuracy towards local S1-servers.)

My BSD server keeps the "master" time for my (two-machine) LAN.
Windows is a client to the BSD machine, which in turn is is a client
to a couple of reliable time servers out on the Net. It all works
extremely well and the machines tend to stay synchronized to well
within perceptual accuracy, although I imagine they are probably out
of sync by some milliseconds (or perhaps not!).

I do occasionally see "failed to synchronize" on the Windows side when
I try to force a synchronization, but when allowed to synchronize on
its own, it's right on the mark.


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