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From: edguer@alpha.ces.cwru.edu (Aydin Edguer)
Newsgroups: comp.mail.misc
Subject: Re: sigh (was Re: Short-circuiting a route)
Message-ID: <432@cwjcc.CWRU.Edu>
Date: 19 Jul 89 19:10:17 GMT
References: <562@daitc.daitc.mil> <12167@polyslo.CalPoly.EDU>
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Reply-To: edguer@ces.cwru.edu (Aydin Edguer)
Organization: CWRU Dept of Computer Engineering and Science
Lines: 40

A while ago I wrote:
 >> Option three is to say that it should try to deliver mail to site "b"
 >> using the information available to it, treating pathalias data as
 >> just another form of MX record.  When looking up a name via the
 >> Domain Name Service (DNS) we accept an MX record to be the equivalent of
 >> a host record for ALL mail purposes (including source routing).
 >> What this option asks us to do is treat a pathalias record as the equivalent
 >> of a host record for mail purposes.

In <the previous article> karl@cis.ohio-state.edu (Karl Kleinpaste) writes:
 [an excellent summary (with one minor mistake) of RFC974 deleted for brevity]
 > ...I submit that the RFC delivery algorithm requires that active
 > reroute of the first hop must occur at each relay point along the path
 > to the destination.
Hmm.  Yes, the RFC974 algorithm may require a reroute of the first hop at
each relay point along the path to the destination.  Note, however this is only
a reroute of THE FIRST HOP and thus would be the same as passive rerouting,
not active (rabid) rerouting.
RFC974 does not say to look down the list trying to find known hosts, it merely
says to look at the first domain (host) in the path and try to reach it.

 > I argue that this is patently silly; that a _requirement_ to reroute
 > actively at each relay is consummately wrong, and hence is to be
 > ignored.  Therefore, I conclude that !-paths must not be source routes
 > if source routes require such mechanisms.
I would agree, if it was a requirement to actively reroute.  It is my opinion,
however, NOT requiring active rerouting.  It is requiring passively rerouting
and thus I still conclude that "!" paths are source routes.

 > Allowing for the following equivalences...
 > SMTP/DNS	UUCP/comp.mail.maps
 > --------	-------------------
 > A records	entries in Systems/L.sys files
 > MX records	pathalias data, usually as compiled into /usr/lib/uucp/paths
This agrees well with my view of the equivalences but minus one addition
I would make.  I submit that the pathalias data also contain CNAME RR's 
(relation records).

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