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From: cliff@garnet.berkeley.edu (Cliff Frost)
Newsgroups: comp.protocols.tcp-ip.domains
Subject: Re: Proposed extensions to MX records.
Message-ID: <1991Apr1.174442.17107@agate.berkeley.edu>
Date: 1 Apr 91 17:44:42 GMT
Article-I.D.: agate.1991Apr1.174442.17107
References: <1991Mar28.182232.13467@agate.berkeley.edu> <9103301612.AA16080@mp.cs.niu.edu>
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In article <9103301612.AA16080@mp.cs.niu.edu> rickert@CS.NIU.EDU ("Neil Rickert, N Illinois U, CS") writes:
>>This proposal implies using Domain Names for routing decisions.  It's always
>>been my understanding that a DNS name implies nothing at all about routing
>>(for IP or mail or anything else).  Is this no longer true?
...
> Whether or not the domain names reflect the packet routing in general, they
>heavily effect mail forwarding based on these policy decisions.

Neil,
How about you change the wording of your proposal very slightly.  Instead of
using "normal" DNS domains, call them "MX-domains".  In the cases where policy
enforces the types of naming you're talking about there is no difference
between a machine's MX-domain and its DNS name's subdomain.

Now, require mailers that implement this to allow a host to think of itself
in multiple MX-domains.  A host would normally be in the same MX-domain
as it's Domain Name, but it could be configured to be in others as well,
and it could also be configured NOT to be in the MX-domain that matches
its Domain Name.  (You do suggest this in your proposal as an option.)

That is; X.FOO.BAR.COM's mailer could be configured to be in the MX-domain
ABC.EDU.  That could be *as well as* being in the MX-domain FOO.BAR.COM, or
it could be *instead* of being in the MX-domain FOO.BAR.COM.  

It seems like the underlying problem to be solved is this:  Given a list of
source and destination IP addresses, an application (eg mail, telnet, ftp),
and a list of policy constraints, how does a host choose which ones to use,
and in what order?

Well, I don't have any brilliant idea how to approach this, so your
proposal seems like a clever way of handling some of this for email. 
I'd just hate to see fine upstanding addresses like rickert@CS.NIU.EDU
degenerate into things like EDU!NIU!CS!rickert.  ;-)

	Cliff