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From: tcp-ip@ucbvax.ARPA
Newsgroups: fa.tcp-ip
Subject: Re:  Voting on time
Message-ID: <10081@ucbvax.ARPA>
Date: Thu, 22-Aug-85 01:37:34 EDT
Article-I.D.: ucbvax.10081
Posted: Thu Aug 22 01:37:34 1985
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Organization: University of California at Berkeley
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From: jsq%tzec.UTEXAS@ut-sally.ARPA (John Quarterman)

	Basically the idea is to avoid asking the operator to set the time
	as much as possible.

Same goal as I had, slightly different assumptions.  I decided not to average
over times from all known time servers because my experience in polling
actual servers is that they tend to cluster in groups of hosts with
times similar to a second or so, but the times of the groups can be
different by as much as a minute or more.  Also, the most accurate group
is almost always the fastest one, not the one in the middle.  And hosts
which set their time directly from WWV or some other accurate outside
source will almost always be more accurate than those which don't,
except for the occasional instances when they're wildly wrong.

Of course, since you choose to poll only your local network, and if
no system on it has a WWV clock, averaging makes much more sense.

Netdate does record the time change in /usr/adm/wtmp properly like /bin/date,
though I neglected to mention it in the manual entry.  I've updated the
manual entry for that and a couple of other omissions, and I've added
a few details to the verbose output option (the network delay is shown).
The result is available by anonymous ftp from ut-sally as ~ftp/pub/netdate.c
and ~ftp/pub/netdate.8.  Also in the same directory are udp.timed.c and
tcp.timed.c, which are implementations of the server end of RFC868,
suitable for use with inetd.  (Chris Kent earlier announced a UDP
time server that doesn't need inetd.)  Some people tried to retrieve
things this morning and couldn't:  we had a hardware problem with
a disk;  it's fixed now.

All these things have been run through lint, and we use them on several
systems here (im4u.ARPA and ut-sally.ARPA run both time servers).
However, they haven't been around long, so don't be surprised if they
have bugs, and please let me know about any you find.