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Subject: Symphony for the Devil (sic)

Date: Friday, 15 February 1985  18:46-EST
From: RMXJITRY%CORNELLA.BITNET at Berkeley
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Re:   (copy) ASK MR. PROTOCOL (#4) "

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From: "Michael O'Brien -- 'Mr. Protocol'" <obrien@CSNET-SH.ARPA>
To: RMXJITRY@CORNELLA.BITNET
Cc: cic@CSNET-SH.ARPA
Subject: ASK MR. PROTOCOL (#4) "Music to My Eyes"
         [Reprinted by permission from CSNET-FORUM, v1 #5, 5 Feb 85.]
Date: 15 Feb 85 12:17:00 EST (Fri)
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Q: You nice folks at the CSNET CIC have given us some "simple, easy
guidelines" on the proper format of mail addresses.  How do you explain
those monsters we keep seeing in real mail?

A: Mr. Protocol is glad you asked.  He has been watching the address wars
for some time now and has been amazed at the creativity shown, not only
by users, but by programs.  He feels that the neglected area of address
composition is one of the most fertile artistic arenas in the latter
half of the Twentieth Century.  While artists are still stupefied by
the invention of photography, and attempt to create works which either
look like giant soup cans, or like nothing at all, and while musicians
attempt to destroy their instruments without losing rhythm, network users
are composing entire symphonies where a simple address would do.

These compositions have a structure familiar to students of music.
They begin with the introduction of a theme, generally involving various
mixtures of host names and exclamation points.  From there they move to
the development, involving more host names, percent signs, and perhaps
the introduction of an actual user name.  There follows a climax, involving
one, two, and possibly even three "@" signs, from which develops a coda
of one or two final host names, plus a domain or three, generally pulled
from the mists of artistic creativity rather than any real specification.
These marvelous creations are then subjected to the tender mercies of
various automatic mail routing systems, which will often, in an attempt
to be helpful, introduce further complexities.  Often the final product,
so far from being legal, cannot be understood by any known entity, human
or mechanical.  (Mr. Procotol regards much electronic music in the same
light, but then he IS a fuddy old so-and-so, isn't he?)

Mr. Protocol is particularly enamored of the solution proposed by Peter
Honeyman, who, given a message which has already traversed a path, is able
to construct the best possible return path using a priori knowledge and a
healthy dose of graph theory.  (See "A Parser for Electronic Mail
Addresses", by Peter Honeyman and Pat E.  Parseghian, PROCEEDINGS, USENIX
Association Winter Conference, Dallas 1985, pp 184-190.)

This theory, of course, only works on healthy addresses, complex as they
may be.  It would take an expert system (or an expert postmaster) to
determine what, if anything, can be done with some of the wonders spewed
forth by the Internet soup.

Let us examine one of these compositions, and see if we can make some sense
of it:

princeton!down!honey%purdue@csnet-relay.ARPA

This pleasant little melody is actually relatively healthy.  While there is
no single Official Specification which describes how to parse it, there are
a number of ad hoc rules which may be applied.  The real problem
represented here is that this address includes pieces of three networks:
UUCP, CSNET, and Internet.

"princeton!down!honey" is in the key of UUCP. "honey" is evidently the user.
However, we do not know offhand if "honey" is at host "down", which we are
supposed to get to from "princeton" via "purdue@csnet-relay.ARPA", or if
the user is really "honey@purdue", and host "down" is supposed to talk to
host "purdue".

Mr. Protocol's long-standing migraine is caused by the fact that there
is no obvious answer to this question.  In fact, he is often to be found
hunched over a glass of milk at his kitchen table at 3 A.M., mourning the
fact that fundamental independence of network addressing schemes means
fundamental ambiguity in network address parsing.

In fact, as Mr. Honeyman has pointed out, only a priori knowledge can
tell us how to parse this example.  We must know either that "princeton"
talks to "purdue" and that "down" does not, or we must know that "honey"
is at "down" and not at "purdue".  (Pop Quiz: Is "purdue" in the key of
UUCP, the key of CSNET, or B-flat Minor?)

All of this assumes that the "@" sign has the loosest binding, and that
the address is to be "cracked" there first.  In cases with multiple "@"
signs, all bets may be off:

honey@princeton!down%purdue@csnet-relay

This thundering piece of network nonsense is typical of the sort of address
which goes nowhere fast. (Mr.  Protocol is reminded of the works of
Mahler, but is much too polite to suggest such a thing.)  This cripple is
destined for the bit basement at some host, and which host that will be
cannot easily be predicted.  In fact, a human who had seen correctly
formatted addresses would probably be able to recast this, but such work is
chancy, and generally beyond the capabilities of automatic programs.  Of
course, there is always the chance that the mail systems along the way will
all happen to do the right thing, in which case the user who originated
this address will continue to use it quite happily, until someone along the
way changes their software and the address breaks forever.

A few simple rules:

1) BE LAZY.  Try to use domain routing where possible.  If your destination
address lies in UUCP-land, try to get someone else to figure out how to do
the work.  The Relay will forward mail sent to "user@host.UUCP" to a host
which can generally figure out a path.

2) STAY ON KEY.  Try to gather together all information having to do with a
single network.  That is, keep all "!"'s together, all "%"'s together, and
please, for the sake of Mr.  Protocol's digestion, and that of all mailers
along the way, try to use only ONE "@" sign.

3) BE CURIOUS.  When in doubt, ask the CSNET CIC.  The wizards here have
been constructing address symphonies for some time, and have some ideas as
to what works and what doesn't.

When domain routing becomes real, all of this external ugliness will
disappear, and be replaced by internal ugliness, hidden from the user.
While this notion often does not work terribly well in society at large, it
is a genuine relief in mail systems.  Of course, this means the Death of
an Art Form, but it was a pretty noisy art form, at that.

[Thanks to "Charlie" <boncelet@udel.ARPA>, for corrections to the
original CSNET-FORUM article. --Mr. P.]