In article ,
David.Russell@dowjones.com (Russell, David) wrote:

> I have a PC running Windows that gets disconnected from the network for
> up to an hour. I am using NTP to sync the clock while it is connected
> but when disconnected the clock drifts quite a bit. Does anyone have

Once stabilised, ntpd should not drift significantly in one hour, assuming
you haven't meddled with maxpoll, which, unfortunately, many people do.
It will typically be polling every 20 minutes and an hour drop out won't
even cause it to declare the sever down.

Either you haven't told us the whole story, e.g. it may be a lap top that
goes into a different power management state for that less than an hour,
or you need to find out why you are not reaching a poll interval of
1024 seconds when you are connected.

PS your subject is confusing as the most common question from Windows
users is about running with no real servers, which might also be considered
standalone.

Russell, David wrote:
> I have a PC running Windows that gets disconnected from the network for
> up to an hour. I am using NTP to sync the clock while it is connected
> but when disconnected the clock drifts quite a bit. Does anyone have
> any suggestions for how I can maintain the timing in this scenario?
>
>
>
> Also, I have been looking for a PCI card that would give me better clock
> accuracy than the standard Windows clock. Sub-millisecond accuracy
> using NTP is the objective.
>
>
>
>
>
> Thanks,
>
>
>
> David Russell

You can purchase a PCI card from either Meinberg Funkurhren or
Symmetricomm. Expect to pay $1100 US and up, especially up! These are
equipped with a precision crystal oscillator, optionally an Oven
Controlled Crystal Oscillator (OCXO). They can be equipped with an
optional GPS receiver. The Symmetricomm products are the BC635PCI
and the BC637PCI (with built in GPS). I don't recall what Meinberg
calls their product.

With GPS input, these products can give you sub-microsecond accuracy.
Even without the GPS input they can keep time as accurately as you can
set the clock. They are overkill for most people.

An inexpensive GPS receiver such as the Garmin GPS18LVC ca. $100 US can
do much the same for you if you can site an antenna with an unobstructed
view of the sky. The principal difference is the "holdover" capability
of Symmetricom and Meinberg products; though they are not, in
themselves, primary standards they are extremely good clocks and will
exhibit extremely low drift.

Russell, David wrote:
> I have a PC running Windows that gets disconnected from the network for
> up to an hour. I am using NTP to sync the clock while it is connected
> but when disconnected the clock drifts quite a bit. Does anyone have
> any suggestions for how I can maintain the timing in this scenario?
>
> Also, I have been looking for a PCI card that would give me better clock
> accuracy than the standard Windows clock. Sub-millisecond accuracy
> using NTP is the objective.

Let's start with the basics. What version of NTP are you running and
what operating system? What's in the drift file and are there any errors
in the application event log?

Danny

The PC is running XP and the Greyware Domain Time II NTP client.

I'll track down the drift file info. Do you think that it should be
possible to maintain the clock accuracy while the PC is unable to
receive any NTP packets?


David

-----Original Message-----
From: Danny Mayer [mailto:mayer@ntp.isc.org]
Sent: Sunday, November 04, 2007 8:24 PM
To: Russell, David
Cc: questions@lists.ntp.org
Subject: Re: Standalone PC Clock Sync

Russell, David wrote:
> I have a PC running Windows that gets disconnected from the network
for
> up to an hour. I am using NTP to sync the clock while it is connected
> but when disconnected the clock drifts quite a bit. Does anyone have
> any suggestions for how I can maintain the timing in this scenario?
>
> Also, I have been looking for a PCI card that would give me better
clock
> accuracy than the standard Windows clock. Sub-millisecond accuracy
> using NTP is the objective.

Let's start with the basics. What version of NTP are you running and
what operating system? What's in the drift file and are there any errors
in the application event log?

Danny

Russell, David wrote:
> The PC is running XP and the Greyware Domain Time II NTP client.
>

I've never heard of it. I managed to track this down. I can't tell a
great deal from what they say since they are short on real technical
details. Some of their charts are incorrect since not only does NTP run
on Windows servers of all flavors, it runs as a service. Not only that
the reference implementation is free and Meinberg has done an excellent
job of packaging it. They also provide a free monitoring utility.

There are some things that the installer does not do, like install
itself on remote systems, though it's possible to script that. It also
does not run on win9x machines. It's not worth the effort.

> I'll track down the drift file info. Do you think that it should be
> possible to maintain the clock accuracy while the PC is unable to
> receive any NTP packets?
>

Don't bother looking for a drift file. I thought you were running the
reference implementation of NTP.

My guess is that it is using SNTP rather than NTP so it's not really
disciplining the clock. The reference implementation of NTP not only
ensures that the time is correct but it also disciplines the frequency
of the clock ticks so that the clock stays accurate even when the client
is not connected to any servers.

You are unlikely to have problems with the clock drifting with the
reference implementation of NTP.

Danny
>
> David

To allay suspicions that this newsgroup might be biased pro-Meinberg,
I'll just add that PCI cards are also available from Hopf: http://ww.hopf.com/.

Paul

Paul.Croome@softwareag.com wrote:
> To allay suspicions that this newsgroup might be biased pro-Meinberg,
> I'll just add that PCI cards are also available from Hopf: http://ww.hopf.com/.
>
> Paul

We try not to be biased about it. There are indeed many vendors who sell
refclock modules and are much cheaper than Meinberg. It depends on your
requirements what you should get and starting from no requirements
anything will do. BTW I assume that the URL you meant
http://www.hopf.com/ since you were missing a w!

Danny