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Path: utzoo!linus!philabs!cmcl2!seismo!umcp-cs!cvl!umd5!zben
From: zben@umd5.UUCP
Newsgroups: net.mail
Subject: Re: Mail routing -- problems showing up
Message-ID: <686@umd5.UUCP>
Date: Mon, 29-Jul-85 19:39:24 EDT
Article-I.D.: umd5.686
Posted: Mon Jul 29 19:39:24 1985
Date-Received: Wed, 31-Jul-85 22:40:46 EDT
References: <3018@nsc.UUCP> <2875@topaz.ARPA> <536@down.FUN>
Reply-To: zben@umd5.UUCP (Ben Cranston)
Organization: U of Md, CSC, College Park, Md
Lines: 52
Summary: Agree with breaking syntax loose from semantics

In article <536@down.FUN> honey@down.FUN (Peter Honeyman) writes:
>let me join in hedrick's request that gateways between dissimilar
>networks do the dirty work of translating between addressing styles.
>then i'll send him mail at topaz!rutgers!hedrick, and he'll send me
>mail at honey%princeton@topaz; naturally, the gateway at topaz will
>translate the addresses as they pass through.
>
>i must disagree with his suggestion that we tie transport to syntax:
>graph traversals are everything.  give me a sequence of hosts, in any
>damn syntax you please, and i'll betcha i can get the mail through.
>but on the whole, hedrick is right on the mark.
>
Agree.  A least-common denominator between most (all?) networks is an
ordered list of site names (followed by a user name, to be sure).  The
exact syntax is irrelevant:

    @umd2,@maryland:user@eneevax
    user%eneevax%maryland@umd2
    umd2!maryland!eneevax!user

Specify exactly the same information:  the message is to go to machine
umd2, then to maryland, then to eneevax, then to the specified user.
Unfortunately, when rooted at say UMDA (IBM 4341) this path involves
bitnet from umda to umd2, arpa from umd2 to maryland, and uucp from
maryland to eneevax.  This is not a misuse of the arpanet, as the link
from umd2 to maryland is entirely our local etherstuff, and never passes
through an arpa tip or imp or whatever.

I tell the people on umda to send mail to:

     maryland!eneevax!user@umd2

BitNet gets it to umd2, where my software lives.  I fudge translate the
"maryland!eneevax!user" string to "eneevax!user@maryland" in the arpanet
send program itself, just to get it up there.  If the mailer at umda were
just a LITTLE bit smarter I could have them code it as:

     umd2!maryland!eneevax!user

and be done with it.  This scheme is based on a subroutine to extract the
"next" site name from an address, and to return the "rest" of the address
(remaining site names, or just user name).  The only arbitraryness is in
which order it looks for each syntax - I do @ first, then %, then !, then
RFC733 (user AT site) ugh but advisories from the IBM machines come back
in that syntax so I gotta do it.

Conclusion/summary: visualizing mail addresses as an ordered list of sites,
followed by a user name, is a useful abstraction, and can be used to some
effectiveness when multi-net addresses must be processed.

-- 
Ben Cranston  ...{seismo!umcp-cs,ihnp4!rlgvax}!cvl!umd5!zben  zben@umd2.ARPA