Edward,
The loop time constant varies directly with the poll interval. See "How
NTP Works" in the current documentation. Note that the default value and
range are purposely optimized for public time servers in order to manage
network overhead and are not appropriate for the most accurate LAN
servers. For that the poll interval and thus loop time constant should
be clamped below this, but not below 4 (16 s) for typical 100-Mb/s networks.
Dave
Mischanko, Edward T wrote:
Dave,
How do I adjust the loop time constant so that it is shorter??
The integral component should be retained. The effect of having too
long a loop time constant should be that the system fails to track
clock
wander, so would be more vulnerable to temperature changes or
forgetting
to disable power management of clock frequency.
-----Original Message-----
On Behalf Of David Woolley
Sent: Monday, May 16, 2011 2:01 AM
To: questions@lists.ntp.org
Subject: Re: [ntp:questions] Loop Filter Gains vs. Polling Interval
Mischanko, Edward T wrote:
Can anyone tell me, does the sensitivity for frequency adjustment
lessen
as the polling interval increases? I ask because I'm observing that
my
They are linked, but I have a feeling that the loop time constant is not
clamped, even though the poll interval is. The aim is to always achieve
a certain level of oversampling. At the very least, the intent is to
vary the time constant and then choose a poll interval that is
appropriate for that.
offset increases and the frequency adjustment decreases to the point I
fall out of sync at polling intervals above 256. What am I doing
wrong?
The integral component should be retained. The effect of having too
long a loop time constant should be that the system fails to track clock
wander, so would be more vulnerable to temperature changes or forgetting
to disable power management of clock frequency.
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