[ntp:questions] NNTP server causing large jumps in time
David Woolley
david at ex.djwhome.demon.co.uk.invalid
Wed May 7 20:35:32 UTC 2008
Dave wrote:
> David Woolley wrote:
ositive and negative steps which approximately balance each other
>> indicate a heavily loaded link with variable and asymmetric
>> propagation delays. Apart from local servers, or your Rubidium PPS,
>> or reducing the traffic, the other solutions are to apply and get the
>> ISP to apply traffic shaping to prioritise NTP traffic, or to use the
>> tinker huff and puff option, noting the health warnings attached to it.
>
>
> I've changed to local servers as suggested
That wasn't my suggestion. The usual location of the problem with
balanced positive and negative steps is the link to your ISP, so using
UK servers wouldn't make a difference.
You've actually got runs of positive and negative steps, which is
worrying. Normally pure runs of postive steps indicate a lost interrupt
problem. Runs in a consistent direction and of similar size and
interval generally indicate that something else is trying to discipline
the clock. Alternating steps in positive and negative directions tends
to indicate an overloaded, asymmetric link, but if you have a severe
problem you tend to have the server rejected (which is why the problem
is less common with analogue modems), rather than accumulating a large
correction.
Missed interrupts may be a problem if runs last long enough for ntpd to
adapt to the new, effective, frequency.
>
> server 0.uk.pool.ntp.org
> server 1.uk.pool.ntp.org
> server 2.uk.pool.ntp.org
> server 3.uk.pool.ntp.org
>
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