jantypas@hope.UUCP (John Antypas) (11/17/86)
Well everythings been changed on me. I used to know my way on the net
pretty well and could get mail just about anywhere point A and B might
be. But now all this has changed. How can UUCP sites have a .COM
domain? I was always told that meant an ARPA/DARPA address.
Could someone please explain what all of these new domains mean?
John Antypas:
uucp (I think):
...!{ucivax,sdcsvax,ucbvax!ucdavis}!ucrmath!hope!jantypas
arpa:
ucrmath!hope!jantypas@sdcsvax.ucsd.edurpw3@amdcad.UUCP (Rob Warnock) (11/18/86)
[Note: I am posting this, rather than mailing, since there may well be others simply too shy or confused about all this to say anything. To the network- savvy, please excuse any over-simplifications in the following semi-tutorial.] [Note 2: In an example below, I used "decwrl" as a "gateway" into ".dec.com". There may well be better gateways to ".dec.com" from your site. Please check before wiring that one into anything.] You asked: +--------------- | Well everythings been changed on me. I used to know my way on the net | pretty well and could get mail just about anywhere point A and B might | be. But now all this has changed. How can UUCP sites have a .COM | domain? I was always told that meant an ARPA/DARPA address. | Could someone please explain what all of these new domains mean? | John Antypas: +--------------- A. GO READ "SMAIL" DOCS -- "INFO-*" If you have the "smail" distribution that recently came over mod.sources, look at the "INFO-xxx" files the shar produces. They have a lot of detail on what's happening. (Then, install "smail"...) Briefly though, EVERYONE is getting away from network-dependent addresses. The UUCP people finally lobbied enough to be allowed to set up a zone of registration (those are technical terms) for each of ".{edu,com,...}" for those sites/sub-domains which are primarily UUCP users, and most of the big UUCP sites have been registering as ".com", ".edu", etc. The "smail" program makes a UUCP site "smart" about domains. (You can use it with or without "sendmail", so it's o.k. on old v.7 or new System V's.) The "smart" sites know about domains, "dumb" ones don't. Smart sites ALWAYS send out UUCP mail that never, never, has any "@" signs, sites which have to support both UUCP (with "!") and RFC-822 mail (with "@"s) don't get confused. B. WHAT WAS WRONG WITH "!", ANYWAY? Why go to all this trouble? The problem was, what does the address "abc!def!ghi@xyz.arpa" really mean? It COULD mean any of: (1) Send via SMTP to host "xyz", and let them worry about it. This is the default for sites that only know about RFC-822, since "!" is not a special character in RFC-822. (2) Send via UUCP to "abc", and let them worry about it. This is the default for a (non-smail) UUCP-only site. But what if your site handled BOTH? What do you do? Which do you place more priority to, the "!" or the "@"? Some attempts were made (especially fancy "sendmail.cf" files) to make the choice depending on what kind of transport medium the mail came to you on, but all were less than totally satisfactory. And worse, there was no safe way to say: (3) Send via UUCP to "abc", then via SMTP to "xyz", then via UUCP to "def", and give to user "ghi". because you never knew what host "abc" was going to do with it. They just might: (4) Send via UUCP to "abc", then via UUCP to "def", then via SMTP to "xyz", and then complain about no such user "ghi"! Each site along the way might have a different way of prioritizing the "!" vs "@" decision. C. ENTER THE "DOT" So what the "uucp-project" folks did was decide on a syntax for representing domain-style names unambiguously in old UUCP syntax, WITH NO "@" SIGNS, so that the mail could get through. It was simplicity in itself. Since all domain-style names have at least one "." in them (if written out fully), any UUCP "host" with a "." in it must really be a domain name, and you can freely re-write "user@dom.ain" as "dom.ain!user", and vice-versa. This allows you to sneak domain addresses past intermediate sites who might want to fiddle with the address (like, parse an "@"). It also gives you an unambiguous canonical representation of an address, to say what you really mean. Case in point: In the example above, if you wanted (1) The ARPA site to send out UUCP, then write "xyz.arpa!abd!def!ghi". (2) UUCP all the way to "xyz", use "abc!def!xyz.arpa!ghi". (3) UUCP==>ARPA==>UUCP, then write "abc!xyz.arpa!def!ghi". Clearly, when a host gets a message to parse and the first part is a domain, it needs to know how to handle that (including you -- go install "smail"). But what this does is allow humans to quit worrying about routes, and just give addresses, in the "user@domain" form. "Smail" (with help from pathalias, and usually, from sendmail) handles putting that in a form that will sneak through the UUCP mail system. D. ENTER "GATEWAYS" Suppose you want to send to "joe@blow.dec.com", but you don't know how to get there, but you DO know that UUCP site "decwrl" is willing to act as a gateway for mail into the DEC domain, and that a path to "decwrl" is "gorp!blat!decwrl".Now "decwrl" understands the UUCP domain stuff, but you're not too sure about "gorp" and "blat". They may have ARPA or BITNET connections, and maybe they'll eat an "@", if you give them the chance. To head them off, send your mail to: gorp!blat!decwrl!blow.dec.com!joe In fact, for ANY domain or partial domain, if you know a UUCP path to a "smart" site that knows how to handle UUCP "domains" and understands the target domain (even if YOU don't), you can send to: path!...!to!...!smartsite!dom.ain!user (In fact, the "smart" host may not know everything; but it may know how to route to a "smarter" host.) From the UUCP point of view, any smart host (i.e., understands domains) that knows how to route to (or towards) some given domain can act as a "gateway" for that domain (sort of). E. "SMAIL" AND "PATHALIAS" AND THE UUCP MAPS The "smail" program knows about the stuff I've mentined above (including a lot of details I've glossed over), but the main thing is does for you is: 1. Auto-routes "abc!..." even if you don't talk to "abc", as long as there is an entry in the paths database for "abc". 2. Auto-routes to a "gateway" (in the UUCP sense) for a domain, as long as there is an entry for that domain (or a partial version of it) in the paths database. That means that once your paths database has the entry: .dec.com gorp!blat!decwrl!%s you can send mail with mail joe@blow.dec.com" and simply not worry about it. Smail will look up "blow.dec.com" in the paths file, (probably) not find it, look up ".dec.com", find it, and call "uux" to send your request to "gorp". In detail, it will: /usr/bin/uux - -r gorp!rmail '(blat!decwrl!blow.dec.com!joe)' The "paths" database gets built with "pathalias" (q.v.), which I won't go into here. (You *did* say you were pretty familiar with the old stuff. Well, pathalias hasn't really changed much.) What has changed is that the UUCP maps are getting new "d.*" files which list "gateways" for "domains", in addition to the old-style "u.*" listings. Pathalias will eat these maps to, and produce databases that "smail" will use to route to the listed domains. (In fact, if you only talk to one main other host -- say, if you're a small PC somewhere -- and your mail feed runs "smail", you can just put a domain/gateway entries in for your neighbor, and forget the database!) F. SAY AGAIN, WHERE DID "GATEWAYS" FIT IN? Well, now that UUCP folk have started calling themselves "sue@myco.com", if ARPAnauts want to send mail, the ARPAnet name server has got to know where "myco.com" is, or (*Ta-DAH!*) where a "mail forwarder" for that domain is. This is done with what are called "MX" records in the name server. (See RFC-i_forget_the_number.) And what the UUCP registration zone has been doing is making sure that for each domain registered in ".edu", ".com", etc., in the UUCP zone, that there is an "MX" record available to the name servers. Now when people send in their registrations (see the "smail" distribution for the blank forms), there is a place to specify the mail forwarder, or "gateway". The trouble is, there was an example of "seismo", and too many people just left it that way (not so nice for "seismo"!). Hence the problem of allocating UUCP "gateways"... G. WHAT ABOUT ALL THE OLD UUCP SITES? First, as many as possible should use "smail", 'cause it IS nice, BUT... they don't have to change at all. The "u.*" map files still exist (for a while), and "smail" understands the pseudo-domain ".uucp" and handles it. And the canonical form for domain names WHEN SENT VIA UUCP has no "@" in it, and the dots "." should only be parsed by "smart" (smail) sites. So as long as SOMEBODY continues to admit in a map entry that they talk UUCP mail to your site "oldfolks", then anyone in the net (well, anyone who uses uses "smail" or equiv.) will be able to reach you as: you@oldfolks.uucp H. MORAL Go read the "smail" docs. Install smail. And relax. For once, things ARE getting better... (p.s. If I have given "sendmail" scant coverage above, its because "smail" can be used with or without "sendmail", and is worth it in either case.) Rob Warnock Systems Architecture Consultant UUCP: {amdcad,fortune,sun}!redwood!rpw3 DDD: (415)572-2607 USPS: 627 26th Ave, San Mateo, CA 94403
UH2@PSUVM.BITNET (11/18/86)
You ask how Unix land can have .com or .edu type addresses? Simple, at least as I understand it. There is a massive effort to convert all the nets to this type of "domain" addressing, with only Bitnet lagging a little behind. (My Bitnet node seems to handle them.) If your machine can find, say, erie.psu.edu in its database, fine--it send the message by whatever path is associated with that name. Else, it tries to send it to psu.edu, and hopes that psu.edu will know where erie is. As erie adds, say, a LAN with a bunch of departmental machines, they introduce those machines to erie.psu.edu, and modify software for gatewaying to the lan. Then, if you send mail to pluto.erie.psu.edu, there is a good chance that it'll get there. If you send to user@psu.edu, because you know that user is at Penn State, there is a good chance that psu will know user is in erie, erie will know that user gets mail on pluto, and you won't have to know all the stuff. I learned all this stuff last summer at UseNix, in Atlanta. I seem to recall that several net-gods were at the top of this project and doing all the work, such as writing, debugging, and distributing new software. The biggest problem is getting small machines to install the new software so get after your sysadmin. lee sailer