RFC 2163 (rfc2163) - Page 2 of 26

Using the Internet DNS to Distribute MIXER Conformant Global Address Mapping (MCGAM)

RFC 2163                      MIXER MCGAM                   January 1998


1. Introduction

   The connectivity between the Internet SMTP mail and other mail
   services, including the Internet X.400 mail and the commercial X.400
   service providers, is assured by the Mail eXchanger (MX) record
   information distributed via the Internet Domain Name System (DNS). A
   number of documents then specify in details how to convert or encode
   addresses from/to RFC 822 style to the other mail system syntax.
   However, only conversion methods provide, via some algorithm or a set
   of mapping rules, a smooth translation, resulting in addresses
   indistinguishable from the native ones in both RFC 822 and foreign
   world.

   MIXER describes a set of mappings (MIXER Conformant Global Address
   Mapping - MCGAM) which will enable interworking between systems
   operating the CCITT X.400 (1984/88/92) Recommendations and systems
   using using the RFC 822 mail protocol, or protocols derived from
   RFC 822. That document addresses conversion of services, addresses,
   message envelopes, and message bodies between the two mail systems.
   This document is concerned with one aspect of MIXER: the mechanism
   for mapping between X.400 O/R addresses and RFC 822 domain names. As
   described in Appendix F of MIXER, implementation of the mappings
   requires a database which maps between X.400 O/R addresses and domain
   names; in RFC 1327 this database was statically defined.

   The original approach in RFC 1327 required many efforts to maintain
   the correct mapping: all the gateways needed to get coherent tables
   to apply the same mappings, the conversion tables had to be
   distributed among all the operational gateways, and also every update
   needed to be distributed.

   The concept of mapping rules distribution and use has been revised in
   the new MIXER specification, introducing the concept of MIXER
   Conformant Global Address Mapping (MCGAM). A MCGAM does not need to
   be globally installed by any MIXER conformant gateway in the world
   any more. However MIXER requires now efficient methods to publish its
   MCGAM.

   Static tables are one of the possible methods to publish MCGAM.
   However this static mechanism requires quite a long time to be spent
   modifying and distributing the information, putting heavy constraints
   on the time schedule of every update.  In fact it does not appear
   efficient compared to the Internet Domain Name Service (DNS).  More
   over it does not look feasible to distribute the database to a large
   number of other useful applications, like local address converters,
   e-mail User Agents or any other tool requiring the mapping rules to
   produce correct results.




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