[time-nuts] leontp offset

Hal Murray hmurray at megapathdsl.net
Thu Oct 20 16:06:34 EDT 2016


> full disclosure: there were a couple of outlier external clocks I threw out,
> one with a 38 ms offset and the other with a 112 ms offset).

That's not uncommon.  It happens more often when the server is farther away 
and there are more opportunities for strange network routing.

The NIST servers in Gaithersburg MD (near Washington DC) have been off by 30 
ms for a while.  There was a discussion on some list several months back.  I 
forget which one.

>  What's worrying is that both arbiters off by the same-ish amount.  This
> indicates something systemic in the way we do things. 

My guess is that the PPS is 10 ms wide and somebody is triggering on the 
wrong edge.  10 ms is small enough that unless something like this happens 
nobody would notice.  (I wonder if they are selling into the financial 
market.)

Are you getting time from the Arbiters via Ethernet or PPS over a serial 
connection?  If you are getting it via PPS, ntpd has a simple fudge flag to 
use the other edge.  If you are getting it via Ethernet, then the problem is 
inside their box which make it harder to fix but also stranger that nobody 
else noticed sooner.



-- 
These are my opinions.  I hate spam.





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