[ntp:questions] Win7: ntpd adjusting time backwards

Jeroen Mostert jmostert at xs4all.nl
Sun Dec 9 16:26:15 UTC 2012


On 2012-12-09 17:00, David Taylor wrote:
> On 09/12/2012 15:00, Jeroen Mostert wrote:
>> It is a shame that nothing *outside* the reference documentation (in
>> particular quick-start guides) seems to describe the use of this option,
>> though. It's also unfortunate that ntpd has been around so long (with
>> relatively few changes) that outdated documentation is a dime a dozen.
>
> Nothing describes "pool"? Well, my Windows set-up page (also referenced by
> Meinberg) does for a start.
>
Yes indeed: "David Taylor created a detailed step-by-step walkthrough of the 
installation on his website."

Pshaw! As if I'm going to read some step-by-step walkthrough! There's 
screenshots below the thing, right? This David Taylor guy can't possibly have 
something more interesting to say.

The above is, of course, steeped in irony, since your site is a veritable 
treasure trove for people setting up NTP under Windows. I really wish I'd 
stumbled across it sooner. I know I didn't find it through the Meinberg site.

> As I mentioned, I haven't tried Internet servers alone recently on Windows
> except for one brief test with Windows-8 (because it has more precise time
> routines):
>
> http://www.satsignal.eu/ntp/Win-8+Internet.html
>
> and I did a test with a Linux server, WAN-only as well:
>
> http://www.satsignal.eu/ntp/2012-11-10-11-12-raspi1_ntp-b-day.png
>
> If precise timekeeping is important, it may be worth upgrading to Windows-8
> (although I saw an improvement on only one of two PCs tested).
>
As long as Microsoft still doesn't make it possible to upgrade the kernel 
without upgrading the shell, that's not going to happen, because the Windows 8 
UI is a serious productivity killer for me.

The broader context is that I'm working on an NTP setup for a "real" network, 
where the only demand is that the servers stay within each other's times to some 
reasonable degree (I'll take anything <= 10 ms), with only very lax demands on 
synchronizing to absolute time. I've already discovered that this is actually 
fairly easy as long as all machines sync to a single local server with some 
frequency (setting minpoll 4 maxpoll 4 is no problem on a LAN, of course, and 
keeps even the most wayward machines in line). I'm still happy I ran into 
problems locally, because upgrading to 4.2.7 significantly reduces jitter even 
in this setup (as reported by your site as well), so I'll be sure to slipstream 
that in.

Of course, upgrading all machines to Windows 8/Windows Server 2012 just to get 
better time synchronization isn't going to happen. :-)

For now the local server is a Windows Server 2008 machine, but I've already 
petitioned for a dedicated Linux machine (FreeBSD would be too "out there" for 
IT, I'm afraid...) If possible, we can later upgrade that to something with a 
GPS, but it's probably not necessary at the moment.

> It may well be that 30 - 40 ms is the best you can expect without some local
> server (e.g. FreeBSD/Linux/Win-8 box on your LAN), but stepping every hour
> should not normally be happening.

If 30-40 ms is realistic for syncing to internet time, I'll take it. Though it's 
slightly disappointing, but I guess the limitation is in Windows more than it is 
in NTP.

-- 
J.



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