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From: stodola@FCCC.EDU (Bob Stodola)
Newsgroups: comp.protocols.tcp-ip.domains
Subject: Re: Experimental DNS RFC (Re: MX Records)
Message-ID: <9104101350.AA10282@relay.fccc.edu>
Date: 10 Apr 91 13:50:45 GMT
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I read with great interest the proposal for LMX RR's.  While I see the
purpose (indeed, campus mail routing here goes through all sorts of
channels, and keeping it straight is a headache).  I have three reasons
why this proposal is not an ideal solution to this problem:

	1.  I am not sure that it is not redundant.  Higher preference MX's
	    (lower numbered) citing systems which are not accessible to the
	    outside world are one of the cited purposes of MX preference
	    codes -- outside mailers simply fail to find the internally
	    accessible systems, and proceed to find the gateway system.
	    In the context of the example in the XRFC, the DNS entries would
	    be:
		public.rutgers.edu  MX 0 public.rutgers.edu
		                    MX 10 gateway.rutgers.edu
	    Outsiders will fail on delivery to public and then try gateway.
	    Gateway is supposed to know that it cannot attempt delivery to
	    preference values  equal to or greater than itself, and should
	    attempt delivery to public.

	2.  It is unclear what I would put in the LMX RDATA field that would
	    eliminate the need for an external routing database.  For example,
	    our campus mailer delivers mail to systems via TCP/IP, DECNet,
	    appletalk shared disks, serial dial-up connections and other more
	    bizzare routing.  If you need the external routing database,
	    the LMX seems to be an unnecessary level of complication.

	3.  Given that the information has no value whatsoever to the outside
	    world, I'm a little uncomfortable including it in the IN class
	    database (as opposed to the HS or ?? class).


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Robert K. Stodola                            Phone: (215) 728-3660
Manager, Research Computing Services         FAX: (215) 728-3574
The Fox Chase Cancer Center                  internet: stodola@fccc.edu
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