Stratum one autonomy and assumptions about GPS

[Eric S. Raymond]

Achim Gratz <Stromeko at nexgo.de>:
> Forget about GPS outages.  If you want to connect these time servers to
> the net, they should have some form of sanity checking that's
> independent from their primary time source and take them off the net as
> soon as something looks fishy.

What kind of sanity checking do you recommend?

>                             I frequently see .GPS. falsetickers in
> NTPpool (actually the last month I haven't seen them, so maybe they've
> been kicked out) that are/were 50ms and more out, which tells me they
> have either not bothered to determine the fudge factors or run without
> PPS.  You don't want to see that kind of stratum-1 clock on a larger
> scale.

My recipe/HOWTO does emphasize that you need 1PPS for Stratum 1 service.
Beyond that I don't know there's much I can do to head off operator error.

How do you fudge a 1PPS source?  What do you have that you consider
more accurate?
-- 
		<a href="http://www.catb.org/~esr/">Eric S. Raymond</a>