[ntp:questions] Isolated Network Drift Problem

David Woolley david at ex.djwhome.demon.co.uk.invalid
Wed Nov 26 07:51:54 UTC 2008

Cal Webster wrote:

> 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

A server needs a reference clock, or a fictional one, like the Local 
Clock driver.  It will serve time without one, but proper clients will 
ignore it.

> 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
> all.

Including the Local Clock driver on leaf nodes will make the system less 
reliable and make it more difficult to detect when things have broken, 
but should have absolutely no effect on time keeping, when the system is 
working properly.


> 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.

As a last resort, yes.

> 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

With that number of machines, a radio clock will be a negligible 
additional cost.

> 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.

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