Preliminary results of using GPS to look for clock skew

Dave Taht dave.taht at
Fri Sep 23 06:10:30 EDT 2011

On Wed, Sep 21, 2011 at 7:11 PM, Eric Raymond <esr at> wrote:

> If we need rawstats in a form for real-time monitoring, why not modify
> NTP to optionally multicast them and avoid all this going to disk?

I have been collecting rawstats statistics for some time now on ntp
server currently dedicated to prototyping this stuff. 5 ntp servers comes
to about 45K/day - and /tmp is a ramdisk on the router, which has about
32MB to spare most of the time. So a plan - not the best one - was
to upload the latest rawstats file every day and delete 2 day old entries
in cron.

> I
> have good relations with the NTP guys, and they wouldn't be likely to
> resist a feature request with a network-health-monitoring use case
> even if we didn't. Let's *use* that zorch for something, rather than
> fielding a fragile pile of hacks.

I would like very much like to not field a fragile pile of hacks but
the ntp people  I've talked to reflexively (and rightly) seem focused
on means to get good time, come hell or high water, rather than
collecting and analyzing the outlier data as to why bad data is

That said, adding a data message of some sort to propagate
rawstats-like data to a given server configured to receive it would be

2) Also on my list is to get ntp doing the right thing in the case of
dnssec enabled startup without valid time. There is a

Multiple means to do this have been described here:

I guess this somewhat separate convo should move to the ntp list.

I'd taken a look at the ntp codebase and it was convoluted enough to
make me wish someone familiar with the ntp codebase would tackle the
dnssec problem - when ntp is started with -g, to get the initial time
with dnssec validation disabled, then revalidate the dns entries after
the clock is slewed.

Regrettably I think the best long term solution to the dnssec problem
that there should be a flag to getaddrinfo in the libc as described

in use to tell it not to validate dns, as it's only a single bit, darn
it!!, but that implies a whole standardization process, and hacking
the libcs etc, etc....

It just seems too heavyweight to add a dependency on libval for ntp
for a single bit...

to bring this back to getting time via gps somewhat, it takes a long
time to get a lock from a gps signal to set the clock, too...

I've had chicago's "does anybody really know what time it is" stuck in
my head for weeks now.

> --
>                <a href="">Eric S. Raymond</a>

Dave Täht
SKYPE: davetaht
US Tel: 1-239-829-5608

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