SUMMARY: time sync'ing a network

From: Uri Guttman (
Date: Fri Aug 16 1991 - 16:05:31 CDT

I received many replies to my request for time sync'ing a local network
and I thank all of you. The leads finally pointed me to two major
sources of information which I cannot summarize here, but I will
describe what is available.

The Network Time Protocol is now an Internet standard can keep a network
of cpu's to about +/- 10 ms. of each other. It uses a tree of time hosts
and there are many master hosts on the net. The source for NTP as well
as a large amount of related text is available via ftp from in pub/ntp. Specifically clock.txt lists major time
hosts and radio/atomic clocks you can use to sync your cpu's. NTP comes
in version 2 and version 3 and a flavor called XNTP. I don't know the
differences but the documents in louie should help. Much of the work on
NTP seems to have been done at the U. of Delaware by David L. Mills
which is why they have a master archive of NTP source.

A newsgroup that discusses NTP is comp.protocols.time.ntp. You can get
much more help than I could give you by making queries there.

If you keep a master timehost set as accurately as you wish by hand (I
call New England Telephone which still has a dial-the-time number) you
can have the clients run rdate in cron and maybe in /etc/rc to set the
time during booting. This will work to within +/- 10 seconds which is
good enough for non-critical situations. Otherwise use NTP.


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