X.500 and Domains
RFC 1279

Document Type RFC - Experimental (November 1991; No errata)
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Network Working Group                            S.E. Hardcastle-Kille
Requests for Comments 1279                   University College London
                                                         November 1991

                          X.500 and Domains

Status of this Memo
    This memo defines an Experimental Protocol for the Internet
    community.  Discussion and suggestions for improvement are
    requested.  Please refer to the current edition of the ``IAB
    Official Protocol Standards'' for the standardization state and
    status of this protocol.  Distribution of this memo is unlimited.

    This RFCconsiders X.500 in relation to Internet and UK Domains.
    A basic model of X.500 providing a higher level and more
    descriptive naming structure is emphasised.  In addition, a
    mapping of domains onto X.500 is proposed, which gives a range of
    new management and user facilities over and above those currently
    available.  This specification proposes an experimental new
    mechanism to access and manage domain information on the Internet
    and in the UK Academic Community.  There is no current intention
    to provide an operational replacement for DNS.

RFC 1279                X.500 and Domains                November 1991

1  The Domain Name System

The Domain (Nameserver) System (DNS) provides a hierarchical resource
labelling system [Moc87a] [Moc87b] [Lar83].  Example domains are:


Entries usually have a single name, although pointers to entries (not
subtrees) may be provided by CNAME records.  Information (resource
records) is associated with each entry.  Name components are typically
chosen to be shortish (e.g., ``CS'').
RFC 822 mailbox names are closely related [Cro82].  For example:


The local-part of the RFC 822 mailbox can be considered as one level
lower in the domain hierarchy.

2  X.500

The OSI Directory, usually known as X.500, provides a very general
naming framework [CCI88].  A basic usage of X.500 is to provide
Organisationally Structured Names.  A Schema for this is defined
within the standard.  Name components will typically have longish
values.  This is an example directory name represented in Tabular

           Country              GB
           Organisation         University College London
           Organisational Unit  Computer Science
           Common Name          Stephen E. Hardcastle-Kille

This can also be written in the ``User Friendly Name'' notation
defined in [HK91].  This syntax is used for names in the rest of this

    Stephen E. Hardcastle-Kille, Computer Science,

Hardcastle-Kille                                                Page 1

RFC 1279                X.500 and Domains                November 1991

    University College London, GB

This type of structure is termed ``organisational X.500''.  This is a
subset of the general capabilities.

3  The basic model

    X.500 has as much relation to the DNS as DNS has to ARP. Paul

This is, essentially, the position adopted here.  The basic model is
that organisational X.500 is providing a layer of naming at the level
above domain names.  These structured names can be considered to form
a naming layer above domain names.  There are the following key

 o  Organisational X.500 tends to use longer and more descriptive

 o  The organisational X.500 DIT is slightly shallower than the DNS

 o  X.500 has a richer information framework than DNS

These differences suggest that the following should NOT be done:

 o  Represent X.500 information in the DNS

 o  Have an algorithmic mapping between the two hierarchies

This note proposes to represent DNS information in the DIT, and to
provide for a loose coupling between the two trees.  This note does
not propose an equivalencing of X.500 and Domains.

The proposed model is illustrated in Figure 1.  Both an organisational
and domain structure is represented in the DIT, by use of appropriate
object classes and attribute types.  A weak linkage is provided
between the two parts of the tree by use of special attributes.  Here,
the linkage is 1:1, but it may be more complex for some parts of the
organisational DIT or domain namespace.  The linkage is achieved by
use of special attributes, as described in Section 11.

Hardcastle-Kille                                                Page 2

RFC 1279                X.500 and Domains                November 1991

                  j jZ Z

               j j       ZZ
            jj              Z Z
        jjj                    ZZ

Domain Component=UK          Country Name=GB
Domain Component=AC       Organisation Name=Univeristy College London

                        *        BB
              ss                  BBB

Domain Component=UCL      Org Unit Name=Computer Science
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