Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site ncr-sd.UUCP Path: utzoo!linus!decvax!ittatc!dcdwest!sdcsvax!ncr-sd!greg From: greg@ncr-sd.UUCP (Greg Noel) Newsgroups: net.mail Subject: Re: More thoughts on mail relays Message-ID: <322@ncr-sd.UUCP> Date: Tue, 5-Nov-85 17:57:25 EST Article-I.D.: ncr-sd.322 Posted: Tue Nov 5 17:57:25 1985 Date-Received: Fri, 8-Nov-85 08:15:27 EST References: <1813@umcp-cs.UUCP> <1746@peora.UUCP> <909@plus5.UUCP> <1761@peora.UUCP> Reply-To: greg@ncr-sd.UUCP (Greg Noel) Organization: NCR Corporation, Torrey Pines Lines: 68 I don't want to enter this philosophical debate; I think the two sides are both right and wrong, and that the discussion will eventually reveal that they are trying to do the same thing different ways, and that the cross-fertilization of ideas will be mutually beneficial. But I do want to point out one misconception that shows that the issue is more subtle than meets the eye. In article <1761@peora.UUCP> jer@peora.UUCP (J. Eric Roskos) writes: > ..... what's the difference between (assuming >a site that only has Unix mail and no router) writing > > petsd!vax135!ucbvax!sam@slowvax.ARPA >or > petsd!vax135!ucbvax!slowvax.ARPA!sam > >It just involves permuting the last two name tokens, and replacing the last >@ with a !. No, this doesn't work. As a case in point, Peter Honeyman sent me a note last week. I presume that he just used the reverse path of a news item rather than calculating the path, since the message went from his machine (down) to princeton to seismo, then over the ARPAnet to noscvax, then via UUCP to me. If you look at the reverse path at each point, it is: hop 1 -- down!honey hop 2 -- princeton!down!honey hop 3 -- princeton!down!honey@seismo.something.GOV hop 4 -- noscvax!princeton!down!honey@seismo.something.GOV Applying the simple algorithm above, this reverse route becomes noscvax!princeton!down!seismo.something.GOV!honey instead of the correct noscvax!seismo.something.GOV!princeton!down!honey which would reach him, assuming that noscvax would handle this form of address (I don't know if it does). This is yet another case of the confusion between an \address/ and a \route/ and each network's bias toward one over the other. In terms of the discussion before us, what would happen to your first example if vax135 suddenly became an ARPAnet gateway? Then it would have both @ and ! routing available, and it would be able to reach \both/ possible destinations; it would have a hard time deciding what to do with the message. The point is that \you/ would have to change how the mail is sent, based upon a change in status that you can't control and of which you may not even be aware. >However, I wrote the router with the intent that someday it would become >a gateway, since we have machines here that are not on the UUCP network. >If we ever make that conversion, I will have to add the change to rmail >which the person at NCR in Torrey Pines recommended awhile back, whereby >the domain table also specifies the program to run to exit the UUCP network Hmmmmm..... Thank you, I think, although that is not quite what I was recommending -- I wanted the "UUCP network" just to be a special case of a generalized network routing, handled by the same logic as all other networks and invoked in the same manner as all other networks. The thing I was trying to emphasize was that network routing is something that can be done pretty much indepentantly of the details of how the route is physically implemented; in other words, to borrow an expression out of context, that the physical transport layer is a implementation decision that can be factored out of the choice of which link is to be chosen to use for the message. Perhaps when our copy of smail arrives (that's a \hint/, Mark), I will have a chance to actually explore some of those ideas -- it may turn out that the seperation between decision and implementation isn't workable for some reason we don't yet know. I didn't get a chance to proof this for spelling; I hope it isn't \too/ awful. -- -- Greg Noel, NCR Rancho Bernardo Greg@ncr-sd.UUCP or Greg@nosc.ARPA