Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84 SMI; site sun.uucp Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!mhuxt!houxm!mtuxo!mtunh!mtung!mtunf!ariel!vax135!petsd!pesnta!amd!amdcad!decwrl!sun!guy From: guy@sun.uucp (Guy Harris) Newsgroups: net.mail.headers Subject: Re: RFC920 domains Message-ID: <2373@sun.uucp> Date: Tue, 2-Jul-85 02:47:37 EDT Article-I.D.: sun.2373 Posted: Tue Jul 2 02:47:37 1985 Date-Received: Thu, 4-Jul-85 04:58:05 EDT References: <918@sdcsvax.UUCP> <532@deepthot.UUCP> Organization: Sun Microsystems, Inc. Lines: 48 > Domain naming schemes relate to routing as follows: If you don't know > how to route a message directly, you FORWARD the message to someone that > you hope will know better. In general this means a server for the given > domain. Do you mean "network" (i.e., ARPANET/Internet, UUCP net, CSNET, etc.) or "domain"? A lot of the confusion in this debate is caused by thinking that there is a one-to-one correspondence between networks and domains. This need not be the case. Some systems assume that there is such a correspondence (i.e., some "sendmail.cf" files use a UUCP route generator and mailer if they see a host name that ends with ".UUCP", and use an ARPANET SMTP mail connection if they see a host name that ends with ".ARPA" - or route mail to a host with an ARPANET connection if they see ".ARPA"), but a host in domain ".COM" may be on the UUCP network, the ARPANET, or some private network. You can do routing by "brute force" by having a huge database of hosts and routes to them, or you could send all your outgoing mail to a "big brother" who does the routing for you, or... Think of name-to-(best)-route as a function (if a host has two or more equally good routes to it, pick one randomly). The value of a function from one finite set to another for a particular member of its domain can be computed by table lookup (i.e., the route database) or by "cleverer" techniques. Encoding part of the value in the input (i.e., using network names as domain names) is one such technique. However, this puts constraints on the use of domains; domains were intended as a way to simplify the administration of a host namespace, not as a way of cataloging all electronic mail networks. You can debate whether the UUCP network should be a domain with subdomains assigned for routing convenience, but it's not a foregone conclusion that this is the best way to go. > The problem lies in making sure that you are really getting closer. That > is, that the host you forward to has a *better* idea (or at least equally > good) of where to pass the message to. This way, routing can be done just > one hop at a time. > > It doesn't matter whether you use geographic regions, corporate > affiliations, or any other scheme to create the subdomains. Everyone > shouldn't have to know the route to everybody else and those that don't > should use the domain structures for partial routing. If you choose "any other scheme" to create the subdomains, you can choose one where the domains are set up for administrative convenience, not routing convenience, in which case there's no way to tell what a "closer" host might be simply by looking at the components of the target host's name. Guy Harris