Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!gatech!cwjcc!charlie!edguer
From: edguer@charlie.CES.CWRU.Edu (Aydin Edguer)
Newsgroups: comp.mail.misc
Subject: Re: sigh (was Re: Short-circuiting a route)
Message-ID: <423@cwjcc.CWRU.Edu>
Date: 13 Jul 89 21:57:22 GMT
References: <562@daitc.daitc.mil> <12167@polyslo.CalPoly.EDU> <VIXIE.89Jul5150330@bacchus.pa.dec.com> <1888@prune.bbn.com>
Sender: news@cwjcc.CWRU.Edu
Reply-To: edguer@ces.cwru.edu (Aydin Edguer)
Organization: CWRU Dept of Computer Engineering and Science, Cleveland, OH
Lines: 79

In article <1888@prune.bbn.com> rsalz@bbn.com (Rich Salz) writes:
 >In article <VIXIE.89Jul5150330@bacchus.pa.dec.com> (Paul Vixie) writes:
 >>The Moral: don't short-circuit.
 >
 >Wrong.  The Moral:  don't put full domain names into email paths if
 >they're going through the Internet and you don't want them short-circuited.
 >Hack the path to be something like
 >	noe!packet_radio!kg6kf_ampr_org!callsign!callsign
Wrong.  The Moral: if you want to play in the game,
		   don't skip some of the rules.

 >>I'd better say it again, several times, since people always mix this up:
 >>	if you don't like the paths people use, change the source mailers
 >
 >If you shoot mail into the Internet with a fully-qualified domain name
 >in the address -- yes, Paul, even if it's in the Path line -- than you
 >should expect people to follow it.
That's right :-)  I should expect people to follow the path I have given
them.

Rich, I disagree with you.  I refer you specifically to "the rules."

According to RFC 822, pages 32-33

 ]   6.2.7.  EXPLICIT PATH SPECIFICATION
 ]
 ]      At times, a  message  originator  may  wish  to  indicate  the
 ]      transmission  path  that  a  message  should  follow.  This is
 ]      called source routing.  The normal addressing scheme, used  in
 ]      an  addr-spec,  is  carefully separated from such information;
 ]      the <route> portion of a route-addr is provided for such occa-
 ]      sions.  It specifies the sequence of hosts and/or transmission
 ]      services that are  to  be  traversed.   Both  domain-refs  and
 ]      domain-literals may be used.

This means that if you are given an explicit source route, YOU SHOULD
OBEY IT.  It's in the rules in black and white (or whatever the colors
are on your printer or display).

If I hand you a path <@prune.bbn.com,@bacchus.pa.dec.com:edguer@ces.cwru.edu>
you should hand it to bacchus.pa.dec.com.  To do otherwise is a violation
of RFC 822.  Period.  No looking ahead.  No getting smart.

I agree it is frowned upon to use source routes:
From RFC 822, page 33

 ]      Note:  The use of source routing is discouraged.   Unless  the
 ]             sender has special need of path restriction, the choice
 ]             of transmission route should be left to the mail  tran-
 ]             sport service.

but if given one you should obey it.

The rules for translating between UUCP and the Internet are contained in
RFC 976.  I quote:

RFC 976, page 7

 ] 3.  Algorithm
 ]
 ]    The algorithm for delivering a message to an address "user@domain"
 ]    over UUCP links can be summarized as follows:
 ]
 ]       a.  If the address is actually of the form @domain1:user@domain2,
 ]           the "domain" used for the remainder should be "domain1"
 ]           instead of "domain2", and the bang form reads
 ]           domain1!domain2!user.

This leads me to believe that there should a direct mapping from "proper"
"!" notation to "proper" RFC 822 and back (in the absence of mixed notations).
This means that a "proper" Class C host should treat a bang path as a
source route and SHOULD NOT MESS WITH IT.

I think that if everyone wants to follow the rules then active rerouting
should be EXTREMELY frowned upon.  Passive rerouting (the UUCP equivalent
of an MX record) is good.

Aydin Edguer		+1 216 368 6123		edguer@alpha.ces.cwru.edu
Department of Computer Engineering, Crawford Hall, Case Western Reserve Univ.