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From: dan@SCI.CCNY.CUNY.EDU (Dan Schlitt)
Newsgroups: comp.protocols.tcp-ip.domains
Subject: Re: Proposed extensions to MX records.
Message-ID: <9104051527.AA18234@sci.ccny.cuny.edu>
Date: 5 Apr 91 15:27:00 GMT
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I have been following this discussion with some interest but with not much
of an idea on what would constitute a really good solution.  From the amount
of discussion it is clear that there is a real problem to be solved.

In my mind there is a problem with the use of preferences in the way that
has been suggested.  There is simply no way that the use of these numbers 
can be made uniform.  It is a bit like port numbers.  There are reserved 
port numbers that are assigned by the NIC.  That part works well because
they are centrally assigned.  But there is the hack of privileged ports which
gives special meaning to a subset and some, but not all, software treats them
in that way (at least that is how I remeber the situation to be).  That 
creates problems for people who assume that they are treated specially when
they communicate with software that doesn't make that assumption.  You are
setting up a similar situation for MX records.

Before adopting the proposal we ought to see some analysis that establishes
that the system is robust in the face of failure of opposite ends of a
connection making differing assumptions.  I think I saw the start of this
kind of analysis but it wasn't very convincing.

The second problem is that the DNS translates names to numbers and doesn't
have anything to do with routing.  This problem is really about routing.
Is there a solution within the realm of routing without bringing the
DNS directly into it?  Could we drag the solution back into the domain of
assigned numbers?  Is it possible that autonomous system numbers or something
like them could be a better way to attack the problem?  (Said by someone
who knows and wants to know little about EGP and friends.)

/dan