Using the Internet DNS to Distribute MIXER Conformant Global Address Mapping (MCGAM)
RFC 2163

Document Type RFC - Proposed Standard (January 1998; No errata)
Updated by RFC 3597
Obsoletes RFC 1664
Author Claudio Allocchio 
Last updated 2013-03-02
Stream Internet Engineering Task Force (IETF)
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IESG IESG state RFC 2163 (Proposed Standard)
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Network Working Group                                       C. Allocchio
Request for Comments: 2163                                    GARR-Italy
Obsoletes: 1664                                             January 1998
Category: Standards Track

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

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (1998).  All Rights Reserved.


   This memo is the complete technical specification to store in the
   Internet Domain Name System (DNS) the mapping information (MCGAM)
   needed by MIXER conformant e-mail gateways and other tools to map
   RFC822 domain names into X.400 O/R names and vice versa.  Mapping
   information can be managed in a distributed rather than a centralised
   way. Organizations can publish their MIXER mapping or preferred
   gateway routing information using just local resources (their local
   DNS server), avoiding the need for a strong coordination with any
   centralised organization. MIXER conformant gateways and tools located
   on Internet hosts can retrieve the mapping information querying the
   DNS instead of having fixed tables which need to be centrally updated
   and distributed.

   This memo obsoletes RFC1664. It includes the changes introduced by
   MIXER specification with respect to RFC1327: the new 'gate1' (O/R
   addresses to domain) table is fully supported. Full backward
   compatibility with RFC1664 specification is mantained, too.

   RFC1664 was a joint effort of IETF X400 operation working group
   (x400ops) and TERENA (formely named "RARE") Mail and Messaging
   working group (WG-MSG). This update was performed by the IETF MIXER
   working group.

Allocchio                   Standards Track                     [Page 1]
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 RFC822 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 RFC822 and foreign

   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 RFC822 mail protocol, or protocols derived from
   RFC822. 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 RFC822 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 RFC1327 this database was statically defined.

   The original approach in RFC1327 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

   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.

Allocchio                   Standards Track                     [Page 2]
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