Joshua Coombs wrote:
My test server aided with rrdtool has narrowed down my pool of potential
remote ntp servers to 17 healthy candidates with consistent latency, low
jitter, and similar theories on the one true tick. That gives me 4 to
hand to each of my peered internal servers, plus an extra to toss on at
random.
One of these servers is dialing NIST periodically. With the server set
it has, it never raises the polling interval from min (12) and never
chooses it as a time source. The jitter seems rather high as well. I
was under the impression that if I used the two NIST numbers, the
refclock driver could deduce the line latency automatically (always
reads 0 on the scoreboard) and took multiple samples per call to reduce
jitter. Should I be using 'burst' on that server statement (is that
even valid?). I'd like to see the server stretch the poll interval up
to the max if it can, seems like calling NIST every hour is a bit extreme.
Also, as that server has access to a reference clock, would I be better
served configuring just my peers on it and no external ip servers,
instead putting them on my 3 other internal servers?
I've also seen mention of using burst with extended intervals for remote
time sources mentioned in a few places. If I only have a given remote
time source configured on one server, is using burst with a maxpoll of
11 considered abusive? Should I bump my minpoll if I do?
Joshua Coombs
Please be very careful about using burst. Burst sends eight requests at
every poll interval and creates an undue burden on the server. It is a
special purpose hack not intended for general use. The documentation is
not very clear about exactly what circumstances justify its use.
Burst should only be used with the knowledge and consent of the victim.
Do not confuse burst and iburst. Iburst is good, it sends an intial
burst of eight requests before beginning to poll at normal intervals; it
gets you a fast startup and, provided you do not restart ntpd every few
minutes does not place an undue burden on the server.
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