Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!cs.utexas.edu!tut.cis.ohio-state.edu!snorkelwacker!ira.uka.de!smurf!urlichs
From: urlichs@smurf.sub.org (Matthias Urlichs)
Newsgroups: comp.mail.uucp
Subject: Re: Paths and Precedence (Re: Question about From: lines)
Message-ID: <[$6je2.vl6@smurf.sub.org>
Date: 13 Jul 90 22:52:25 GMT
References: <3RK4TQE@xds13.ferranti.com> <269B6560.3F1E@intercon.com> <S2M4Q11@xds13.ferranti.com>
Organization: University of Karlsruhe, FRG
Lines: 48

In comp.mail.uucp, article <S2M4Q11@xds13.ferranti.com>,
  peter@ficc.ferranti.com (Peter da Silva) writes:
< In article <269B6560.3F1E@intercon.com> amanda@mermaid.intercon.com (Amanda Walker) writes:
< > We don't.  You send paths through UUCP.  The fact that currently you can
< > "tunnel" UUCP paths through the internet is a bug, not a feature.  Once
< > mail gets to the Internet, it should have an address, not a route.
< 
< That's all very well, but in the real world you have little UUCP trees
< hanging off the internet, and pathalias gives you a nice little bang path
< all the way through to the end.
< Your idealism is commendable, but for the forseeable future it's going to
< be necessary to "tunnel" uucp paths through the internet. So how does one
< do it?

I'm currently running my mailer (MMDF, with the UUCP stuff somewhat modified)
based on the reasonable assumption that anyone hanging off me has either
Pathalias, is on the Internet, or is a node with one single connection (to
me).
So I don't generate paths, I generate "uux - nexthop!rmail user@somewhere"
(with 'somewhere' either a FQDN or a hostname.UUCP), or somewhere!user for the
one site which can't understand the former yet.
Mangling Pathalias output to do the same is real easy via a simple sed script,
which transforms
	host: hop1!hop2!hop3!host!%s
into
	host: hop1!host!%s
and which is left as an exercise to the reader.)

This is based on the simple assumption that the next site along the path
really should know better how to get to the destination than I do, since it's
assumed to be closer to it.
Of course, that Internet site, probably not running Pathalias, might need
another FQDN so that it will know where to send that mail. (Why is no one
offering .UUCP MX service? Just distill the pointers from the maps, everyone
should be happy -- right?) A Perl script which analyzes the raw maps will help
determine the FQDN of the correct host; I'm currently testing it.

The equivalent operation on the other side of the mailer, called "Rerouting",
is kind of a religious issue by itself... Right now I'm chopping off incoming
elements from the left until I either see the end (i.e. a user name) or an
unknown host, and then back off one. It has yet to break anything at this
site; in this is differs from the widely used method of examining the path
from the right and stopping at the first _known_ host, which _does_ break
things.)

-- 
Matthias Urlichs -- urlichs@smurf.sub.org -- urlichs@smurf.ira.uka.de
Humboldtstrasse 7 - 7500 Karlsruhe 1 - FRG -- +49+721+621127(Voice)/621227(PEP)