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From: Stef@ics.uci.edu (Einar Stefferud)
Newsgroups: comp.protocols.iso.x400
Subject: Re: Addressibility of UAs?
Message-ID: <18473.674152353@nma.com>
Date: 13 May 91 17:35:42 GMT
Reply-To: Stef@ics.uci.edu
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Approved: usenet@ics.uci.edu
In-reply-to: Your message of 13 May 91 09:12:21 +0000.
             <9105130910.AA05614@jerry.inria.fr>

> "- The MTA controls little more than the country code, ADMD, and PRMD."

> This is "the right thing" according to X.400 84. The other
> attributes should be used as a search key in the local directory,
> which should result in the identification of a "delivery method"...
> Problem is that there was no way to define how several MTAs could
> share the same PRMD in X.400 84...Christian huitema

CCITT had no interest in how routing would be doen inside a PRMD, and
so left it as "a local matter".  This was actually a very wise
decision, though it does not provide a "cook book" receipe for the
unintiated (or the unanointed).

The basic fact remains, learned from internet experience with domain
names used for mail addresses, that rotuing is best done by taking the
entire address as a key, and doing a "longest match" on this
"address-as-a-key" to find the preferred next hop from the table.

Of course, the table has to be constructed so that the "longest match"
is indeed the preferred next hop, adn so it is easy to find in the
normal process of table lookup.

Now, with more experience, includijg the thought of dealing with
multiple ADMDs from a single PRMD, and dealing with complex PRMD
situations with shared domains (another cold dash of hard reality), it
should be clear that the "key" for table lookup should utilize every
relevant bit of "per-recipient+per-domain" information that the MTA
can gets its hands on, and had best be able to do sophisticated things
with that information.

This will be required to provide "bill control" where-in a PRMD
selects routes to ADMDs based on tarrif tables for routing domains,
and on security considerations for security reasons, and on quality of
service considerations, and on where spcific individual recipients
actually are from time to time.

Routing is not a simple thing, and it is not the business of CCITT to
specifiy how it is to be done by any PRMD.

The business of interpreting CCITT silence to mean anytnign was (and
is) a big mistake.  The silence only means that their lips were not
moving.  It also means that they did not know what to say, or they
wisely recognized that it is not their province to say anything about
intra-PRMD routing.

Suffice to note that some of us will do it better than others, for
whatever this sage observation may be worth.

Best...\Stef