Path: utzoo!utgpu!water!watmath!clyde!att!ucbvax!decwrl!palo-alto!vixie
From: vixie@palo-alto.DEC.COM (Paul Vixie)
Newsgroups: comp.mail.uucp
Subject: why you should say "-d rutgers -d sun" in your pathalias command line
Message-ID: <3674@palo-alto.DEC.COM>
Date: 4 Aug 88 21:04:18 GMT
References: <676@bacchus.DEC.COM> <881@vsi1.UUCP> <Aug.4.13.20.49.1988.373@pilot.njin.net>
Organization: DEC Western Research Lab
Lines: 75


				R U T G E R S

brisco@pilot.njin.net (Thomas Paul Brisco) writes:
# 	In fact, there is nothing wrong will letting your MTA do all
# the routing for you.  I've had very few sites bouncing back to me,
# and I _usually_ route through rutgers.  

This depends on what you mean by "all your routing".

Rutgers does it WRONG.  BIG TIME EL WRONGO.  Always has, always will.

If I send to <...!rutgers!foo!bar!person>, and rutgers looks in its map
database and says "oh, site <<<bar>>> can be reached through ...!baz!bar!user",
IT HAS JUST DONE THE WRONG THING.

<baz!bar!user> is never nec'ily the same person as <foo!bar!user>.  <<<bar>>>
can be contextual: <baz!bar> and <foo!bar> aren't nec'ily the same machine.

This is not "routing", it's <<<rerouting>>> and it's EVIL and RUDE.

Now, if I send mail to <rutgers!bar!user>, then rutgers is free to send to
whatever entity it calls "bar", whether a direct UUCP neighbor or an indirect
neighbor reachable only through a routing database.  This is "routing" and
it's very convenient.  Many sites do this.  Smail does this (by default,
unless misconfigured with a stupid option that shouldn't be in there).

Rule of thumb:
	Don't look for a route in your UUCP map database / pathalias database
	unless you are about to throw the message away out of unreachability
	of the "next host" in the source route.


				   S U N

Sun thinks it owns the world.  I send mail from my home machine (vixie.uucp)
with a From: line like this:

	From: vixie!paul

or like this:

	From: paul@vixie.UUCP (this is ugly and bad)

If this message passes through pacbell, or decwrl, or ubvax, or uunet, or
half a dozen other major sites within one or two hops of vixie.UUCP, the
message is forwarded on with a From: line that looks like this:

	From: vixie!paul

Note that it's the same as I left it.  Note that the From_ line (sometimes
called the UUCP From_ line) is growing and probably looks like:

	From pacbell!vixie!paul <date>

Which is okay.  But if this message goes through Sun.COM, it will be forwarded
on with a From: line like this:

	From: vixie!paul@Sun.COM

This is EVIL and RUDE.  Sun doesn't talk to vixie.UUCP; replies to the
message are broken, Sun.COM bounces things that come to it looking like:

	To: vixie!paul@Sun.COM

The mistake?  Sun is rewriting HEADER sender addresses; it's only supposed
to rewrite ENVELOPE sender addresses unless the message is passing into the
internal network (inside Sun).

						Paul
-- 
Paul Vixie
Digital Equipment Corporation	Work:  vixie@dec.com	Play:  paul@vixie.UUCP
Western Research Laboratory	 uunet!decwrl!vixie	   uunet!vixie!paul
Palo Alto, California, USA	  +1 415 853 6600	   +1 415 864 7013