[ntp:questions] Trying to use Dimension 4 time keeper

David Taylor david-taylor at blueyonder.co.uk.invalid
Sun Sep 15 06:53:46 UTC 2013

On 14/09/2013 21:39, W. eWatson wrote:
> A little bit of data from the two XP PCs:
> Older and more troublesome PC
>   Jitter high 300-650
>   Offset around 685
>   Delay about 100.xxx
>   Reach 80  jumped to 377 an hour later
>   One * for the single pool
> Newer XP
>   Jitter low, 11-8
>   Reach 377
>   * + - + - on five servers
>   Delay 100-150
> Those are fairly rough, as seen in a five minute span. To really make
> any progress I would think a monitor of the data would be more helpful.
> I noticed Broken Clock in the documentation mentioned above. It looks
> tricky to evaluate.
> In my situation, I would be happy if one of the important parameters
> would sound an alarm in my den when one went out of bounds. Fat chance
> of that.

How are you connected to the Internet?  Let's start with your newer PC. 
  The delay of 100-150 ms is much higher than I would expect for a 
direct "fast" Internet connection, it sounds more like dial-up.  If you 
are using the "pool" directive as I suggested (NTP 4.2.6p5 required), I 
would expect to see more than five servers listed.

You can monitor by enabling the statistics collection within NTP, and by 
using MRTG as explained on my Web site:


If statistics are enabled, both Meinberg and I offer plotting programs:


The "Broken clock" problem may manifest itself by NTP reporting that it 
is stepping the clock, or even giving up.  Look for NTP entries in the 
event log to monitor this.

To get alarm monitoring, you could use SNMP (although that's not yet in 
the Windows port of NTP), or you could write a small Perl script to be 
run once every few minutes by the Task Scheduler, which checked the 
parameters you want to monitor by running the appropriate ntpq command, 
and which then sounded the alarm as required.  The alarm could be a wave 
file which you play - perhaps even inside the Perl script.

I have Perl script examples on my Web site at the first URL I gave, and 
there is information here:


on playing .WAV files with Perl in Windows.  Sounds like a good Autumn 

Having said all of that, my situation a decade back was similar to yours 
- wanting to have several Windows PCs well synced.  Were I to be 
tackling the same problem today, I would spend less than US $50 on a 
Linux PC (Raspberry Pi) and sync it to my Internet sources, and then 
sync the Windows PCs to the Raspberry Pi (using a much shorter poll 
interval, 32 seconds, maxpoll 5).  If the location had GPS available 
(e.g. near a window with a sky view) I would spend approx. US $100 
instead and add an Adafruit GPS to the Raspberry Pi, making a unit known 
to correct to a few microseconds, and sync my Windows PCs to that (with 
a "pool" directive for backup).
Web: http://www.satsignal.eu

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