[ntp:questions] ARRGH!!! I woke up to a 50 SECOND clock error.
Ron Frazier (NTP)
timekeepingntplist at c3energy.com
Sat Mar 17 18:27:31 UTC 2012
On 3/17/2012 11:48 AM, David J Taylor wrote:
>> You'd get less jitter with DSL.
>> John Hasler
> You have piqued my interest. I have just set up a Windows-8 PC with
> an ntp configuration not dissimilar to Ron's, in that it's using
> purely Internet servers but trying to monitor a local stratum-1 server
> as well. In essence:
> # Local stratum-1 Free BSD server
> server 192.168.0.3 iburst minpoll 5 maxpoll 5 prefer noselect
> # Seven external servers:
> server x.x.x.uk iburst
> server y.y.y.uk iburst
> server 0.uk.pool.ntp.org iburst
> server 1.uk.pool.ntp.org iburst
> server 2.uk.pool.ntp.org iburst
> server 0.nl.pool.ntp.org iburst
> server 1.nl.pool.ntp.org iburst
> The performance will appear here:
> It will be interesting to see whether the Internet servers poll period
> increased from 64s (I'm hoping that the 32s poll on the local server
> won't affect the Internet ones), and what level of jitter is achieved.
I'm not sure what will happen if you simultaneously prefer and noselect
the local server. Assuming the local stratum 1 server is the most
stable time source, you'll get a much better picture of what the
internet servers are doing relative to it if you allow it to be
selectable as well as being preferred. When you graph it, if the local
server is the active clock, all the lines for the internet servers will
be gathered around and relative to the local server. When I tried to do
things the other way around, with an internet server preferred, the
graph looked awful because there was so much variation. Also, if your
local server starts reporting time that looks too far from the internet
servers, regardless of who's fault it is, ntp will clock hop over to the
I don't THINK your internet servers will ever poll above their default
minpoll value of 6, or 64 seconds.
I realize you don't have a gps attached to this pc, but the iburst lines
reminded me of something. I read somewhere that having iburst on
internet server lines, if a local gps is attached, could prevent the PC
from synchronizing to the gps before it synchronizes to the internet.
On my pc with the gps attached, I don't use the iburst command.
(PS - If you email me and don't get a quick response, don't be concerned.
I get about 300 emails per day from alternate energy mailing lists and
such. I don't always see new messages very quickly. If you need a
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timekeepingdude AT c3energy.com
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