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Path: utzoo!utcsrgv!mart
From: mart@utcsrgv.UUCP (Mart Molle)
Newsgroups: net.followup
Subject: Re: Usenet topology suboptimal.
Message-ID: <3548@utcsrgv.UUCP>
Date: Fri, 16-Mar-84 09:01:50 EST
Article-I.D.: utcsrgv.3548
Posted: Fri Mar 16 09:01:50 1984
Date-Received: Fri, 16-Mar-84 10:52:19 EST
References: <510@psuvm.UUCP>, <353@noscvax.UUCP>
Organization: CSRG, University of Toronto
Lines: 29

The observation that "if you need to go from A to B, you should
do it in one hop" because of the telephone rate structure is 
obvious to anyone who has ever looked at the initial pages of
a telephone book.  Sure, to send a message to your friend on the
opposite coast it is [globally] cheaper to the Usenet community if
you send it yourself in one hop.  The problem is that news is BY
DEFINITION BROADCAST communications, rather than point to point.
Now the issue is how best to distribute each news item to many [5000?] sites.
No-one can afford the dialer time to call all those sites directly,
so the only sensible thing is to treat news distribution as a
hierarchical tree with limited "fan-out" at each node.  Thus, if
a site is willing to exchange news with, say, 5 sites, the average
path length from the originator to everyone else is AT LEAST 6 hops
by analogy with the way "chain letters" grow, i.e.,
	1 + 5 + 5**2 + 5**3 + 5**4 + 5**5 = 3906  [too small]
	1 + 5 + 5**2 + 5**3 + 5**4 + 5**5 + 5**6 = 19531 [ok]
Now, we can't expect all those thousands of sites to be unique,
and the originator probably isn't sitting at the ideal root node
of the tree, even if it IS unique, so it stands to reason that
the path length of news items that you see should be more in the
range of a dozen hops or so.

If you REALLY want to make news more efficient, then talk some
satellite utility out of a communications channel at certain
off-peak hours and have all the "major sites" buy themselves
earth stations.  That way you can use a broadcast channel to
deliver broadcast messages efficiently.  Since dishes for pirating
TV signals from satellites are cheap enough for Joe Public to buy,
the cost of the equipment to bypass Ma Bell shouldn't be that bad.