[ntp:questions] Isolated Network Drift Problem

Cal Webster cwebster at ec.rr.com
Tue Nov 25 23:08:30 UTC 2008

On Tue, 2008-11-25 at 22:23 +0000, David Woolley wrote:
> Cal Webster wrote:
> > 
> > None of our client machines use the local clock. The servers
> configured
> > like this are the other 3 "peer" NTP servers. Don't they need some
> type
> > of time reference if the master server becomes unreachable?
> No.  PCs keep time even without NTP installed.

Okay, I understand that the "PC" (Intel Linux host) will keep time on
its own, albeit at some unpredictable level of accuracy. What I'm not
getting is whether the NTP service running on that host without a local
clock reference will be able to provide time to NTP clients. If so, will
it be more accurate or less accurate if all the NTP peers each use their
own local clock as a time reference as opposed to having no reference at

When I tried removing the "server" and "fudge" lines for the local clock
from ntp.conf but leaving the server lines naming the sister peers,
ntpdq showed nothing in the "peer" or "association" listings.

After communicating with Steve Kostecke and reading the NTP Association
page at ntp.org I'm thinking that a combination of a master server using
a fairly accurate local clock with several Orphan mode servers will work

> ntpd disciplines the local clock.  If you use the local clock as your 
> reference, it will always read exactly the same as the local clock
> being 
> disciplined, so no corrections will ever be made.  You have fallen
> for 
> an urban legend!
> The Local Clock driver is a fiction used to allow an unsynchronised 
> machine to appear synchronised to downstream machines.

Isn't having an "apparently" synchronized NTP server better than having
no NTP server at all? Since we can't all have GPS reference clocks or
Internet connections, some of us have to make use of what we do have.

I'm just looking for the best way to get the most accurate time possible
distributed to a couple hundred machines spread across 15 networks in 3
buildings. Maybe that's asking a lot but that's what I'm aiming to do.
Anything you can do to help would be greatly appreciated.

Thanks! :-)


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