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From: rbraun@spdcc.COM (Rich Braun)
Newsgroups: comp.unix.sysv386
Subject: Re: Network Time Server
Message-ID: <7321@spdcc.SPDCC.COM>
Date: 16 Apr 91 18:04:59 GMT
Organization: Kronos Inc., Waltham, Mass.
Lines: 39

mju@mudos.ann-arbor.mi.us (Marc Unangst) writes:
>You need to designate the master time server...
>
>If the master server drops off the net for some reason, the slave
>timed's are supposed to hold an "election"...
>
>All of this is documented nicely in the timed(1) man page, BTW.

Since my original posting on this thread, I've done some more
experimentation and determined the following in an empirical
way:

	You *cannot* run an isolated subnet with more than one
	"timed -m" running.

The documentation (from both IBM/AIX and SCO/Unix) fails to note
one VERY important fact about the "-m" flag:  it forces the daemon
to pay attention to time-adjustment packets sent from other daemons
also run with the "-m" flag.  This will cause the entire subnet to
lose quite a lot of time each day if two or more "timed -m" daemons
are running, unless you have a periodic task which queries a
reference clock on a rather frequent basis.

I consider this a bug; I'd like to be able to run more than one
daemon capable of picking up where another left off, if the system
goes down for an extended period, but not if I have to give up
accuracy.

So, to summarize:  timed will work fine on an isolated Ethernet as
long as you run it without "-m" on *all* systems except the one which
is most reliable (read: up 99.9999% of the time) and accurate.  As
shipped, SCO Unix doesn't start up timed, but does include "-m" in
the commented-out line; you have to not only uncomment the command
line in /etc/tcp, but also get rid of "-m" on all systems but one.

To SCO and other vendors:  please take a look at this documentation
and/or software deficiency before your next release.  Thanks.

-rich