Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10 5/3/83; site utcsrgv.UUCP 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.