RFC 2163 (rfc2163) - Page 3 of 26

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

RFC 2163                      MIXER MCGAM                   January 1998


   Two much more efficient methods are proposed by MIXER for publication
   of MCGAM: the Internet DNS and X.500. This memo is the complete
   technical specification for publishing MCGAM via Internet DNS.

   A first proposal to use the Internet DNS to store, retrieve and
   maintain those mappings was introduced by two of the authors of
   RFC 1664 (B. Cole and R. Hagens) adopting two new DNS resource record
   (RR)  types: TO-X400 and TO-822. This proposal now adopts a more
   complete strategy, and requires one new RR only. The distribution of
   MCGAMs via DNS is in fact an important service for the whole Internet
   community: it completes the information given by MX resource record
   and it allows to produce clean addresses when messages are exchanged
   among the Internet RFC 822 world and the X.400 one (both Internet and
   Public X.400 service providers).

   A first experiment in using the DNS without expanding the current set
   of RR and using available ones was deployed by some of the authors of
   RFC 1664 at the time of its development. The existing PTR resource
   records were used to store the mapping rules, and a new DNS tree was
   created under the ".it" top level domain. The result of the
   experiment was positive, and a few test applications ran under this
   provisional set up. This test was also very useful in order to define
   a possible migration strategy during the deployment of the new DNS
   containing the new RR. The Internet DNS nameservers wishing to
   provide this mapping information need in fact to be modified to
   support the new RR type, and in the real Internet, due to the large
   number of different implementations, this takes some time.

   The basic idea is to adopt a new DNS RR to store the mapping
   information. The RFC 822 to X.400 mapping rules (including the so
   called 'gate2' rules) will be stored in the ordinary DNS tree, while
   the definition of a new branch of the name space defined under each
   national top level domain is envisaged in order to contain the X.400
   to RFC 822 mappings ('table1' and 'gate1'). A "two-way" mapping
   resolution schema is thus fully implemented.

   The creation of the new domain name space representing the X.400 O/R
   names structure also provides the chance to use the DNS to distribute
   dynamically other X.400 related information, thus solving other
   efficiency problems currently affecting the X.400 MHS service.

   In this paper we will adopt the MCGAM syntax, showing how it can be
   stored into the Internet DNS.








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