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From: buclin@sic.epfl.ch (Bertrand Buclin)
Newsgroups: comp.protocols.iso.x400.gateway
Subject: Re: The disjunct-RFC822 domain problem and DD.RFC-822
Message-ID: <1153@sicsun.epfl.ch>
Date: 28 Feb 91 00:12:36 GMT
Reply-To: Buclin@sic.epfl.ch
Organization: Ecole Polytechnique Federale de Lausanne
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ReSent-From: Jerry Sweet <ifip-gtwy-request@ICS.UCI.EDU>
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Harald,

>Since the gateway got the message from Manchester by SMTP in the first
>place, it seems not unreasonable to impose the condition that it be able
>to return the message to Manchester using SMTP.

This is a political issue ... In Switzerland, it has been decided that all
mail outside a given site is routed using X.400 and not SMTP, even if it is
technically possible (and easier). Incoming mail, could follow whatever route
(direct SMTP, Bitnet, X.400). I don't want to argue on this axiom, but
it fixes the context. Every site has two choices :

- Either it uses X.400 internally (what is generally the case)
- or it has a local gateway able to convert from the internally used mail
  protocol (SMTP, VMS Mail, QuickMail, etc ...) to X.400 (this is the case
  at EPFL).

We then have the situation given by Simon (local SMTP domains, an X.400
backbone, and at the other end of the backbone another RFC987 gateway
for mail directed to Internet).

Now, come back to the example I gave (user%host.decnet@cs.manchester.ac.uk).

>I would assume that the gatewayed address is generated by a gateway that
>gets a message from Manchester on SMTP, and wants to generate an X.400
>address.

Let's make a more general assumption : the mail does not come from any gateway;
the user composes it. He takes the address from anywhere (business card,
publication, from a friend, or whatever source; the point is that a user
sends a mail with that address for the recipient).

>We then have 2 cases:
>1) The gateway has a table entry for it, for example the one you use.

There is no specific entry, the gateway use the generic one for .ac.uk :

ac.uk#PRMD$UK\.AC.ADMD$ .C$GB#

And this leads to the O/R address :

C=GB;A= ;P=UK.AC;O=Manchester;OU=cs;DD.RFC-822=...

As Steve quoted, there is no RFC 987 gateway at Manchester, and if I want
the mail to reach its recipient, the gateway should use the SA :

C=GB;A= ;P=UK.AC;O=mhs-relay;DD.RFC-822=...
(or O=nsfnet-relay or any other SA identifying a valid RFC987 gateway
that serves Manchester).

The current mapping without gateway table assumes that on the path from
my gateway to Manchester there is an MTA which identify the above recipient
address as being aimed to be delivered by it. I think this is quite a strong
hypothesis.

--
Bertrand Buclin                              Internet: Buclin@Sic.Epfl.CH
Service Informatique Central                 X.400:    C=CH;A=ARCOM;P=SWITCH;
Ecole Polytechnique Federale de Lausanne               O=EPFL;OU=SIC;S=Buclin;
CH-1015 Lausanne                             Tel:      +41 21 693 22 11
(Switzerland)                                Fax:      +41 21 693 22 20