Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site mit-eddie.UUCP Path: utzoo!linus!philabs!cmcl2!seismo!harvard!think!mit-eddie!gds From: gds@mit-eddie.UUCP (Greg Skinner) Newsgroups: net.mail Subject: Re: Mail routing -- problems showing up Message-ID: <4941@mit-eddie.UUCP> Date: Mon, 12-Aug-85 17:36:12 EDT Article-I.D.: mit-eddi.4941 Posted: Mon Aug 12 17:36:12 1985 Date-Received: Wed, 14-Aug-85 20:54:07 EDT References: <3018@nsc.UUCP> <2875@topaz.ARPA> <4787@mit-eddie.UUCP> <16110@watmath.UUCP> Distribution: net Organization: MIT Lusers and Hosers Inc., Cambridge, Ma. Lines: 79 First off, let me make myself clear. What I want to be able to do is source-route over different networks. That is to say, I want to be able to specify, via whatever means possible, the route my message takes over whatever networks I see fit to route it through. Excepting in the case where it is illegal to use intermediate networks to transport my messages, I would like to set the precedence of certain network operators (more on this later) so that my messages take the specified routes. Now, about rfc822, source routing, etc. Within a context which understands rfc822, the type of source routing which you give example of <@site1,@site2:user@site3> works. However, over multiple contexts rfc822 source routing does not work, because the non-rfc822 environments most likely will not be able to put the commands together to deliver the mail given the source route. As an example, if I specify my route to be: <@seismo,@ihnp4:gregbo@houxm> what guarantees do I have that seismo knows how to put together the uux command to deliver the mail to ihnp4? Maybe it does, maybe it doesn't. It's possible that seismo will return to mail to me with a ihnp4: Host unknown since ihnp4 is not on the ARPAnet. However, let's assume that seismo is running sendmail and does know that ihnp4 should be looked up in its uuname tables. But then, how do I know that ihnp4 is running sendmail, and can convert gregbo@houxm to what an address looks like in ihnp4's context? (Note: this is just an illustration, and should not be confused with any actual hosts or machines.) Also, it was my impression that quoted strings were not broken up into source routes in SMTP, so that if a user sends mail to "ihnp4!houxm!gregbo"@seismo, the command that is created is <@seismo:ihnp4!houxm!gregbo> and seismo is left to cope with the entire formerly-quoted-string for it's own interpretation, rather than have it pre-interpreted by the ARPAnet. So, I don't believe it is SMTP's job to create end-to-end source routes for mail messages. On the subject of quotes -- quotes were never intended as delimiters for source routes. In rfc822, quotes are used to make tokens out of phrases like "John Smith" or "I. Furious User". The spec mentions nothing about the use of "'s to explicitly specify routes, just as the spec mentions nothing about % as an internetworking character. By using "'s in addresses, one can specify an address such as "John Smith"@somehost, assuming that somehost is capable of mapping "John Smith" to a mailbox or process. Some mailers took the liberty of allowing users to quote a part of an address on the lhs of the @, because the lhs may have had a character in it which had a special interpretation on the host (for example, on tops20 a ! is a comment character). Everything to the left of the @ is left intact for interpretation by the rhs of the @. In conclusion, there is no provision for source routing outside of an rfc822 context specified by rfc822. Whether or not source routing should be allowed outside of the originating context is a subject for much debate, but I hold that it is feasible, especially when sending messages over multiple networks (when it is legal to do so). Domains provide one way of doing this, peter's pathalias scheme seems not to have much knowledge of such things. My proposal, to treat network characters as operators, with grouping of expressions to specify precedence for how addresses are interpreted, is also a subject for much debate, as it has not been proven that such interpretation of addresses is necessary. However, I intend to give it some more thought, and will probably post the same article maybe a year from now if domains or pathalias don't provide neat solutions for the internetworking of mail messages. -- Do not meddle in the affairs of wizards, for they are subtle and quick to anger. Greg Skinner (gregbo) {decvax!genrad, allegra, ihnp4}!mit-eddie!gds gds@mit-eddie.mit.edu