Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uflorida!gatech!bloom-beacon!tut.cis.ohio-state.edu!ucbvax!udel.edu!Mills
From: Mills@udel.edu
Newsgroups: comp.protocols.tcp-ip
Subject: Re:  Internet "time servers" and UNIX timed
Message-ID: <8902081244.aa19879@Huey.UDEL.EDU>
Date: 8 Feb 89 17:44:27 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 38

Dave,

First, please note your list of truechimers is out of date. Fetch the
file pub/ntp/clock.txt from louie.udel.edu as the latest list of servers
that chime the Network TIme Protocol (NTP). See RFC-1059 for a description
of NTP and either Louie Mamakos (louie@trantor.umd.edu) or Mike Petry
(petry@trantor.umd.edu) for the ntpd Unix daemon.

The list of NTP servers cited includes only the Fuzzball NTP servers,
both primary (i.e. directly connected to a radio clock) or secondary
(derives time from a primary clock via the network). There are many
more NTP servers, a few primary and a lot secondary, using ntpd. A
message to the ntp@trantor.edu list should smoke out a few near you.
As suggested in RFC-1059, you may find your needs well met by peering
with a couple of the primary servers on the NSFNET Bluebone (e.g. NCAR,
SDSC or UIUC) and a couple of nearby secondary servers.

NTP is not the only clock in town, even on the Fuzzballs. I found a
couple of thousand responded to either UDP/TIME (37), UDP/NTP (113)
or ICMP/Timestamp in a survey a year ago. While TCP-based time protocols
such as TCP/DAYTIME (13) are available on many machines, I for one
have strongly discouraged using TCP for that, as system resources can
quickly become congested if large numbers of connections are clanking
open and close. Both TIME and NTP can operate over UDP without any
state storage in the server and with only minimal state storage in the
client.

While most organizations I know of that use NTP distribute time within
their system with NTP as well, there is no reason in principle why timed
could not be used within the LAN, other than a small change to the
master-election algorithm. A query to the ntp@trantor.umd list will probably
smoke somebody that has already done that. While not strictly part of NTP
itself, the full accuracy of the service requires that the local-clock
adjustment mechanism by engineered. Both the Fuzzballs and ntpd do a very
careful job of that using phase-lock loop technology. In principle, timed
could do that as well. Maybe somebody will even make that happen.

Dave