[ntp:questions] Tighter regulation?

Mischanko, Edward T Edward.Mischanko at arcelormittal.com
Mon May 20 11:57:16 UTC 2013


David,

The particular client I am monitoring is on an extremely stable corporate
LAN.  The servers are on the same LAN.  Changes in network propagation
are minimal.

The 8 stage minimum delay filter is exactly what I am seeing and exactly
what I would like to disable.  When polling above 256 seconds the amount
of time it takes to make an adjustment is excessive.  Setting maxpoll to
8 does help, but that defeats what server administrators like to have to
reduce loading, on a grand scheme.

I am not sure what jitter will do, but what good is low jitter at the
expense of poor offset correction?

Regards,
Ed
  
> -----Original Message-----
> From: questions-bounces+edward.mischanko=arcelormittal.com at lists.ntp.org
> [mailto:questions-
> bounces+edward.mischanko=arcelormittal.com at lists.ntp.org] On Behalf Of
> David Woolley
> Sent: Monday, May 20, 2013 5:09 AM
> To: questions at lists.ntp.org
> Subject: Re: [ntp:questions] Tighter regulation?
> 
> Mischanko, Edward T wrote:
> 
> > Does anyone know what setting can be changed that will cause
> > tighter regulation of the offset.  My goal is to get clk_wander to
> 
> Why do you want to track network propagation delay changes, at the
> expense of accurate time keeping?
> 
> > equal as close to zero as possible more often.  I would also like
> > to see the frequency adjusted with every change in offset data;
> > it currently does not appear to do that; it seems to be random.
> 
> I think you are seeing the effects of the 8 stage minimum delay filter.
>   Defeating this is likely to increase jitter against true time, as it
> will cause the frequency to be adjusted based on low quality measurement
> samples, increasing the variability of the frequency.
> 
> Note that the time constants for the frequency adjustment loops are
> significantly larger than 8 times the sample interval.
> 
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