Path: utzoo!utgpu!water!watmath!clyde!att!pacbell!lll-tis!kehres
From: kehres@tis.llnl.gov (Tim Kehres)
Newsgroups: comp.mail.uucp
Subject: Re: an example of why I don't believe in automatic routing
Message-ID: <22350@tis.llnl.gov>
Date: 4 Aug 88 02:29:21 GMT
References: <676@bacchus.DEC.COM>
Reply-To: kehres@tis.llnl.gov (Tim Kehres)
Organization: Lawrence Livermore National Laboratory, Livermore CA
Lines: 54

In article <676@bacchus.DEC.COM> reid@decwrl.UUCP (Brian Reid) writes:
> 
> This evening, after weeks of behaving itself, decwrl's pathalias database
> told me that the best route to mcvax from here is 
> 
> sun!daver!altnet!altmail!altger!unido!mcvax!%s
> 
> This is completely preposterous. If my MTA started routing mail along paths
> like this I would newfs it and start using the telephone. I'm sure that if I
> take the trouble to go look (I probably won't) I'll find that according to
> the current pathalias data this really *is* the best path from decwrl to
> mcvax. It's just that pathalias and I have different ideas of what
> constitutes "best". Remember, folks, pathalias believes exactly what you tell
> it.
> 
> Until problems like this stop happening, MTA's should not do routing.

Yes, this is a preposterous route, especially considering you are an internet
site.  It is also highly likely that pathalias thinks that this is a "best"
route from your site to mcvax.  It is also quite true that you can get to 
mcvax in just a few hops from where you are.  If you were to look into what
pathalias generates, I am sure that you could come up with countless other
examples of how the routing could be done in a more efficient and cost
effective way.

This is not however a valid reason for not letting MTA'a handle routing,
whenever an explicit route is not specified.  Some of the reasons most modern 
mail systems are evolving to domain based addressing are:

	o  Optimal source routing can be dynamic and the originator/recipient
	   cannot always determine best routing.

	o  Most users are only concerned about getting their mail through,
	   not how it gets there.  When is the last time you specified the
	   route the postal service should use to get a letter delivered?
	   How many of your users can tell you the best route to mcvax
	   without looking through past mail messages or uucp tables?

	o  The use of a common set of domains makes the use and implementation
	   of gateways between different electronic mail systems easier.  This
	   is one of the reasons for the establishment of standard domain 
	   names.

These are probably not the only reasons, but enough to make the point.
There is sometimes a tradeoff between best routing and making the use of
electronic mail possible for a wider range of users.  Although pathalias
(or the data that gets fed into pathalias) certainly can be improved, it
does help (most of the time) in generating good paths, and provides some
isolation to a wide range of users to routing decisions.

Tim Kehres
Control Data Corporation / Lawrence Livermore National Laboratory
MILNET: kehres@tis.llnl.gov
AT&T:   (415) 463-6852