Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!uunet!seismo!mcvax!cernvax!ethz!peter
From: peter@ethz.UUCP (Peter Beadle)
Newsgroups: comp.mail.uucp,comp.mail.misc
Subject: Re: dynamic routing for UUCP mail
Message-ID: <171@bernina.UUCP>
Date: Wed, 5-Aug-87 05:12:33 EDT
Article-I.D.: bernina.171
Posted: Wed Aug  5 05:12:33 1987
Date-Received: Sat, 8-Aug-87 08:57:39 EDT
References: <915@bsu-cs.UUCP>
Reply-To: peter@bernina.UUCP (Peter Beadle)
Distribution: world
Organization: Institute for Integrated Systems, ETH Zuerich, Switzerland
Lines: 75
Summary: what is a uucp domain address anyway
Xref: mnetor comp.mail.uucp:744 comp.mail.misc:464

Introduction: I manage mail on a cluster of 5 vaxen, 36 sun3's and 2
symbolics work stations with about 12 links and gateways to 3 disparate
networks.  Internal mail is via HoneyDanBer UUCP on ethernet.  External
mail is via uucp, ACSnet and x400. We threw away sendmail about a year
ago and replaced it with upas (which at least has human readable
rewrite files and a name server). At the same time we forcably switched
to doamin addressing for uucp.

Debate: I have never seen smail, we can't run it for political reasons
(Switzerland lacks a top level domain name and somone to administer the
data base) so I think I am eminently qualified to coment about it.

The problem is that people still can't seperate the network transport
level from the mail system. UUCP and UUX (which actually does the work)
copy a file from one unix machine to another and optionally run a
command on the remote machine. That is all they do. Somone a long time
ago thought "why don't I run the mail program on the remote machine so
I can mail between machines". This worked fine at Bell Labs with about
the same number of machines we have (43). Unfortunately the world is a
big place.

More than 10 years on, smail and the whole uucp map project is an
attempt to introduce a routing layer between the the transport layer
(uucp) and the network application (mail). Hopefully one day it will
extend to file transfer and remote job execution like some other more
modern systems.

Smail replaces the rmail link to the mail program with a system that
takes the address on the incoming mail and returns a path route to the
system the mail is destined for from the current host.  A "sensible"
system would then send the mail with its address unchanged to the first
host in the path route where the process would be repeated.

The mail you send to eiger!peter will remain addressed to eiger!peter
even though smail says to route it to
seismo!mcvax!cernvax!ethz!eiger!peter. It will be dispatched from your
system with  a call to uux like:

	uux - -a dhesi seismo!rmail \(eiger!peter\)

We have had a system similar to this working for about 1 year. Explicit
routes go through unchanged so the problem of unregistered machines and
multiple machine names goes away. They are disambiguated by using an
explicit route from a registered host (ethz!tardis!peter works even
though tardis is a machine in sothern california, not Zuerich
Switzerland).

No additional meta characters are introduced.

Routing round dead links becomes easy because you don't have to rip
appart the address to do it.

The only problem of course is that routing has to be done at each node
and each node then has to know at least the first step of how to get to
every other node. This problem was solved long ago with hierarchical
domain addresses such as rfc822.

We finished the system by encoraging people to use rfc822 addresses
instead of ! addressed uucp so we could have minimal routing
information at each node. Of the 3611 remote delivery mail items sent
from our gateway machine since July 7, only 1818 have been ! addressed
(90% of the ! addressed mesages were generated by the nameserver data
base because local ! addresses are marginally faster than rfc
addresses).

Some questions:

1. Is what I have described the original intent of the uucp map/smail
project?

2. If it wasn't the original intent, what way?

Thanks to Rahul Dhesi for raising the problem.

Peter Beadle