Use of the X.500 Directory to support mapping between X.400 and RFC 822 Addresses
RFC 1838

Document Type RFC - Experimental (August 1995; No errata)
Obsoleted by RFC 2164
Author Steve Kille 
Last updated 2013-03-02
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Network Working Group                                           S. Kille
Request for Comments: 1838                              ISODE Consortium
Category: Experimental                                       August 1995

      Use of the X.500 Directory to support mapping between X.400
                         and RFC 822 Addresses

Status of this Memo

   This memo defines an Experimental Protocol for the Internet
   community.  This memo does not specify an Internet standard of any
   kind.  Discussion and suggestions for improvement are requested.
   Distribution of this memo is unlimited.


   This document defines how to use directory to support the mapping
   between X.400 O/R Addresses and mailboxes defined in RFC 1327 [2].

1.  X.400/RFC 822 Mappings

   RFC 1327 defines an algorithm for maintaining a global mapping
   between X.400 and RFC 822 addresses directory [2].  RFC 1327 also
   defines a table based mechanism for maintaining this mapping.  There
   is substantial benefit to maintaining this mapping within the
   directory.  In particular, this will lead to an approach for managing
   the mapping which is both distributed and scalable.

   Mechanisms for representing O/R Address and Domain hierarchies within
   the DIT are defined in [1, 5].  These techniques are used to define
   two independent subtrees in the DIT, which contain the mapping
   information.  The benefits of this approach are:

   1.  The mapping information is kept in a clearly defined area which
       can be widely replicated in an efficient manner.  The tree is
       constrained to hold only information needed to support the
       mapping.  This is important as gateways need good access to the
       entire mapping.

   2.  It facilitates migration from the currently deployed table-based

   3.  It handles the issues of "missing components" in a natural

Kille                         Experimental                      [Page 1]
RFC 1838             RFC 822/X.400 Mapping by X.500          August 1995

          An alternative approach which is not taken is to locate the
          information in the routing subtrees.  The benefits of this
          would be:

        o  It is the "natural" location, and will also help to
           ensure correct administrative authority for a mapping

        o  The tree will usually be accessed for routing, and so it
           will be efficient for addresses which are being routed.

          This is not done, as the benefits of the approach proposed
          are greater.

   There are three mappings, which are represented by two subtrees
   located under:

   OU=X.400/RFC 822 Mapping,  O=Internet

   These subtree roots are of object class subtree, and use the
   mechanism for representing subtrees defined in [4].

   X.400 to RFC 822 This table gives the equivalence mapping from X.400
       to RFC 822.  There is an O/R Address tree under this.  An example
       entry is:

       PRMD=UK.AC, ADMD=Gold 400, C=GB, CN=X.400 to RFC 822,
       OU=X.400/RFC 822 Mapping,  O=Internet

   RFC 822 to X.400 There is a domain tree under this.  This table holds
       the equivalence mapping from RFC 822 to X.400, and the gateway
       mapping defined in RFC 1327.  An example entry is:

       DomainComponent=ISODE, DomainComponent=COM,
       CN=RFC 822 to X.400,
       OU=X.400/RFC 822 Mapping,  O=Internet

   The values of the table mapping are defined by use of two new object
   classes, as specified in Figure 1.  The objects give pointers to the
   mapped components.

Kille                         Experimental                      [Page 2]
RFC 1838             RFC 822/X.400 Mapping by X.500          August 1995

2.  Omitted Components

   In RFC 1327, it is possible to have omitted components in O/R
   Addresses on either side of the mapping.  A mechanism to represent
   such omitted components is defined in Figure 2.

   The attribute at-or-address-component-type is set to the X.500
   attribute type associated with the omitted component (e.g., at-prmd-
   name).  This mechanism is for use only within the X.400 to RFC 822
   subtree and for the at-associated-or-address attribute.

rFC822ToX400Mapping OBJECT-CLASS ::= {
    SUBCLASS OF {domain-component}
    ID oc-rfc822-to-x400-mapping}

x400ToRFC822Mapping OBJECT-CLASS ::= {
    SUBCLASS OF {top}
    MAY CONTAIN {                                                   10
    ID oc-x400-to-rfc822-mapping}

associatedORAddress ATTRIBUTE ::= {
    SUBTYPE OF distinguishedName
    ID at-associated-or-address}

associatedX400Gateway ATTRIBUTE ::= {
    SUBTYPE OF mhs-or-addresses
    ID at-associated-x400-gateway}
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