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To: dbader@umiacs.umd.edu
cc: yokota@zodiac.mech.utsunomiya-u.ac.jp, freebsd-stable@FreeBSD.ORG
From: "Louis A. Mamakos" <louie@TransSys.COM>
Subject: Re: ntpdate (was Re: "saver") 
References: <199707211230.IAA12056@eve.umiacs.umd.edu> 
In-reply-to: Your message of "Mon, 21 Jul 1997 08:30:36 EDT."
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Date: Mon, 21 Jul 1997 22:09:05 -0400
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The "ntpdate" program was primarily intended as a way to get the clock
on your system set with minimal accuracy, say within a few hundred 
milliseconds.  The assumption is that you then start an NTP daemon
which keeps the clock synchronized to a much tighter tolerance.

The long-lived daemon has the ability to better estimate the path 
characteristics over a large number of clock offset/delay samples as
well as being able to do a better job at not trying to synchronize to
an "insane" clock.  Additionally, it can estimate the intrinsic drift
of the clock in your system, and continue to apply frequency corrections
even if it loses contact with it's reference clock.

Running an ntpdate periodically "behind the back" of an NTP daemon throws
much of this out of kilter, and is obviously wrong if you happen to be
running xntpd on your system.  I think having ntpdate in /etc/daily is
really broken unless it's automatically inhibited should you have xntpd
configured to run.

louie