[ntp:questions] Synchronizing to LOCAL(0): Startup time

Richard B. Gilbert rgilbert88 at comcast.net
Mon Oct 15 16:43:29 UTC 2007

Bert Gøtterup Petersen wrote:
> Steve,
> Thanks for the reply, and for the hint toward the ntp-dev version. It does 
> indeed synch to "the local clock" within 1s; GREAT!!!
> In you answer and in several of the other aswers I got, this orphan mode is 
> mentioned. I am not sure I fully get it yet.
> Let me try to answer like this:
> If I have two server products (s1 and s2) and one client (c1), and I want to 
> run them as an 'isolated island' yet locally synchronized (very well).

Depending on how small a difference between server and client you call 
"synchronized (very well)" you may need a hardware reference clock. 
Even if you don't really care exactly what time it is, a reference clock 
gives you an extremely stable reference to synchronize to.  One 
unsynchronized  machine trying to synchronize with another such machine 
can behave very much like one drunken driver trying to follow another. 
With a GPS reference, and a "good" LAN, you can synchronize two machines 
to within a few hundred microseconds.

"Orphan Mode" is a means of "synchronizing" a "time island" using what 
is essentially a randomly selected server.  The machines involved decide 
among themselves who has the "best" clock.  I have never tried it, or 
needed to; I have a GPS reference!  Perhaps someone who has tried it and 
tested the closeness of synchronization can comment.

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