[ntp:questions] Not-So-Newbie question

Peter Laws plaws at ou.edu
Mon Mar 10 16:32:33 UTC 2008

Martin Burnicki wrote:
> Peter,
> Peter Laws wrote:
> [...]
>> Yesterday, I added another Stratum 2 to the group and for some reason, it
>> seems to be taking a long time to get stabilized.  Part of the problem, I
>> think, is that it's running off a Knoppix CD (it's an NPAD test system). I

> Maybe it's a problem of the Linux kernel version you are using. There have

Turns out I'm just not patient enough.  This particular system takes a long 
time to stabilize.  I talked to the folks that put together the Knoppix ISO 
  and they are going to fix the drift file issue in the next release.  I 
could do it myself, but this is a network speed test system and it's much 
easier for me to just be able to 1) reboot if there is any kind of 
compromise and 2) swap CDs and reboot if there is an update to the image.

>> My real question is this:  What am I really looking at in the offset and
>> jitter columns?  What makes a "good server" in terms of ntpq -p output?
>> Low offset?  Low jitter?  Some combination?
> Depending on what causes the jitter and offset. If timekeeping by the kernel
> is poor the this may also cause high jitter and offsets.

I'm really looking for more general answers to this question.

I know (or think I know) that delay is just a measure of how far away 
another server is, offset is just how far off the local system thinks the 
distant server is from the One True Time, and low jitter is good ...

But .... how low does jitter have to be to be "good enough"?  How do the 
three relate to one another?

Peter Laws / N5UWY
National Weather Center / Network Operations Center
University of Oklahoma Information Technology
plaws at ou.edu
Feedback? Contact my director, Craig Cochell, craigc at ou.edu. Thank you!

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