Path: utzoo!utgpu!water!watmath!clyde!cbosgd!ucbvax!UDEL.EDU!Mills
From: Mills@UDEL.EDU
Newsgroups: comp.protocols.tcp-ip
Subject: Re:  Time synchronization and distribution plan
Message-ID: <8801251035.aa07080@Huey.UDEL.EDU>
Date: 25 Jan 88 15:35:10 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 29

Merton,

I don't know where you are as the ionosphere flies, but in my corner of this
world I sure would not trust my WWV receiver to stamp my archives. I would
trust my WWVB receiver rather more, except just now even that signal has
dropped below the floor and the clock is almost a second off. I did in
fact suggest exactly the model you mention, using a more-or-less reliable
local radio clock and verifing sanity with nominal pinging of its friends.
Now, about the protocol to accomplish those pings...

I started in this hokey business mostly to support accurate performance
measurement and analysis of the Internet; however, as time ticked on it
became an end in itself and lots of fun as well. Maybe you don't care about
time to the millisecond, but then you probably don't do any computerized
trading, wide-area monitoring and so forth. For example, with the system
now in place I have been able to compare timestamped error reports collected
from several packet switches and merge them into a scenario accurate to
within the flight time of packets between switches.

Last night I killed first one radio clock and then another untill all WWVB
primary radio clocks were disabled. I verified all the primary and secondary
time servers switched their hierarchical allegance until the ultimate backup
WWV clocks at U Michigan and U Delaware kicked in. So far as I could tell,
all time servers maintained synchronization to within a few tens of
milliseconds throughout the experiment. However, in this case all clocks
were observably sane. The next experiment is to insanitize a couple of them
and verify the rest toss them out of the club.

Dave