Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site ulysses.UUCP Path: utzoo!decvax!ucbvax!ulysses!smb From: smb@ulysses.UUCP (Steven Bellovin) Newsgroups: net.news.config Subject: Re: Abuse of ``DIRECT'' in Usenet maps Message-ID: <1004@ulysses.UUCP> Date: Wed, 10-Jul-85 19:12:40 EDT Article-I.D.: ulysses.1004 Posted: Wed Jul 10 19:12:40 1985 Date-Received: Thu, 11-Jul-85 00:46:46 EDT References: <1738@amdahl.UUCP> <313@phri.UUCP> Organization: AT&T Bell Laboratories, Murray Hill Lines: 49 > gam@amdahl (Gordon A. Moffett) says: > > [...] using the ``DIRECT'' cost value [...] not really DIRECT (or > > DEDICATED) lines, but just ``very good'' DEMAND connections. > > I take this to mean that other people are just as confused as I > am about what the various costs mean. To quote the pathalias man page: > > DIRECT 200 (local call) > DEMAND 300 (normal call) > HOURLY 500 (hourly poll) > EVENING 1800 (time restricted call) > DAILY 5000 (daily poll) > > Can somebody who *really* knows what these are supposed to mean > (i.e. one of the implementors) give some examples of situations that > fall into the various catagories. Back when I wrote pathalias, DIRECT was intended to refer to a direct cable between the tty port on machine A that was connected to a tty port on machine B, where machine B was running a getty. That is, unless the target machine was down or someone was cu'd over this direct wire, the connection should *always* succeed. I rated this as better than demand-dialed, which could fail if the autodialer was busy, all ports on the target machine were busy, the phone system was in some strange state, etc. Given the rather strange phone system in Chapel Hill at the time (a long story I'll tell some other time) and the even stranger autodialer we were using (an even longer story I probably won't tell), plus the fact that one of our primary correspondent machines had only one dial-in line, all of these constraints were very real. So that's the official word on what DIRECT meant *then* -- Peter's probably right about using it for local calls today, though my original intention was to use something like DEMAND+3*HIGH or some such. I also agree with Peter that pathalias has never had a clearly-defined goal it was optimizing towards. The reason is quite simple: no two people could agree. I decided that the primary goal was to get mail through quickly and reliably, which in turn meant using observed frequencies of calling and reliability as the best indicator of (a) the willingness of someone to pay for forwarding mail and news; and (b) the willingness and ability of the system administrator to hold uucp's hand(sic) enough. I made up the initial numbers by defining an important subnet that I knew well (North Carolina plus major backbone sites plus a few hanging off of them), and playing with the values till I got paths that matched what I felt was optimal (given the definition cited above). The net is far larger now, with greater fanout but more sensitivity towards costs; my numbers may no longer be optimal, but I do suggest caution in adjusting them -- the output is very sensitive to minor perturbations in costs. --Steve Bellovin