tcp-ip@ucbvax.ARPA (06/04/85)
From: Christopher A Kent <cak@Purdue.ARPA> Has anyone made the modifications to 4.2 to slave a system's clock to a Fuzzball host? chris ----------
tcp-ip@ucbvax.ARPA (06/05/85)
From: Ron Natalie <ron@BRL.ARPA> Perhaps all the MILNET/ARPANET loading is coming from everybody trying to use DCN machines to set their clocks. -Ron
tcp-ip@ucbvax.ARPA (06/05/85)
From: MILLS@USC-ISID.ARPA In response to the message sent 03 Jun 85 23:35:09 EST (Mon) from cak@Purdue.ARPA Chris, Mike O'Connor (oconnor@dcn9) installed a program on our Sun workstation which mumbles the DCNet protocols via our local Ethernet. Unfortunately, the Sun clock wanders all over the place and is unsuitable for locking to anything better than a windmill generator. I don't think you want the DCNet protocols, anyway, but some sort of similar protocol that operates over real Internet paths. That's not trivial, as a grok at RFC-889 should show. The fuzzies have a highly evolved tracking algorithm involving both linear and nonlinear filtering and estimation in order to achieve the claimed accuracies even on local nets. It would be a useful and positively fascinating exercise to adapt these algorithms to real Internet dynamics using UDP for coarse tracking and ICMP timestamps for fine synchronization. Someone out there should cop a Master's thesis for going after this one with hammer and tongs. Dave -------
tcp-ip@ucbvax.ARPA (06/05/85)
From: Jeff Mogul <mogul@Navajo>
It would be a useful
and positively fascinating exercise to adapt these algorithms to real
Internet dynamics using UDP for coarse tracking and ICMP timestamps for
fine synchronization. Someone out there should cop a Master's thesis for
going after this one with hammer and tongs.
Someone already has copped a PhD thesis for devising some very
elegant algorithms to maintain distributed clocks even when
some clocks are lying. See Keith Marzullo's thesis "Maintaining
the Time in a Distributed System" (Stanford, 1983). His
implementation used Pup rather than IP protocols, but I think the
mapping is obvious. Keith's address is Marzullo.PA@Xerox.
Also see Gusella and Zatti, "TEMPO: Time Services for the
Berkeley Local Network", Berkeley EECS report # UCB/CSD 83/163,
which presents a simpler, although in my opinion inferior, algorithm
using UDP. I can't tell if they got a thesis out of this one or not.