Using Domains in LDAP/X.500 Distinguished Names
RFC 2247

Document Type RFC - Proposed Standard (January 1998; No errata)
Updated by RFC 4519, RFC 4524
Last updated 2013-03-02
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Network Working Group                                           S. Kille
Request for Comments: 2247                                    Isode Ltd.
Category: Standards Track                                        M. Wahl
                                                     Critical Angle Inc.
                                                             A. Grimstad
                                                                    AT&T
                                                                R. Huber
                                                                    AT&T
                                                             S. Sataluri
                                                                    AT&T
                                                            January 1998

            Using Domains in LDAP/X.500 Distinguished Names

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.

1. Abstract

   The Lightweight Directory Access Protocol (LDAP) uses X.500-
   compatible distinguished names [3] for providing unique
   identification of entries.

   This document defines an algorithm by which a name registered with
   the Internet Domain Name Service [2] can be represented as an LDAP
   distinguished name.

2. Background

   The Domain (Nameserver) System (DNS) provides a hierarchical resource
   labeling system.   A name is made up of an ordered set of components,
   each of which are short strings. An example domain name with two
   components would be "CRITICAL-ANGLE.COM".

Kille, et. al.              Standards Track                     [Page 1]
RFC 2247              Using Domains in LDAP/X.500           January 1998

   LDAP-based directories provide a more general hierarchical naming
   framework. A primary difference in specification of distinguished
   names from domain names is that each component of an distinguished
   name has an explicit attribute type indication.

   X.500 does not mandate any particular naming structure.  It does
   contain suggested naming structures which are based on geographic and
   national regions, however there is not currently an established
   registration infrastructure in many regions which would be able to
   assign or ensure uniqueness of names.

   The mechanism described in this document automatically provides an
   enterprise a distinguished name for each domain name it has obtained
   for use in the Internet.  These distinguished names may be used to
   identify objects in an LDAP directory.

   An example distinguished name represented in the LDAP string format
   [3] is "DC=CRITICAL-ANGLE,DC=COM".  As with a domain name, the most
   significant component, closest to the root of the namespace, is
   written last.

   This document does not define how to represent objects which do not
   have domain names.  Nor does this document define the procedure to
   locate an enterprise's LDAP directory server, given their domain
   name.  Such procedures may be defined in future RFCs.

3. Mapping Domain Names into Distinguished Names

   This section defines a subset of the possible distinguished name
   structures for use in representing names allocated in the Internet
   Domain Name System.  It is possible to algorithmically transform any
   Internet domain name into a distinguished name, and to convert these
   distinguished names back into the original domain names.

   The algorithm for transforming a domain name is to begin with an
   empty distinguished name (DN) and then attach Relative Distinguished
   Names (RDNs) for each component of the domain, most significant (e.g.
   rightmost) first. Each of these RDNs is a single
   AttributeTypeAndValue, where the type is the attribute "DC" and the
   value is an IA5 string containing the domain name component.

   Thus the domain name "CS.UCL.AC.UK" can be transformed into

        DC=CS,DC=UCL,DC=AC,DC=UK

Kille, et. al.              Standards Track                     [Page 2]
RFC 2247              Using Domains in LDAP/X.500           January 1998

   Distinguished names in which there are one or more RDNs, all
   containing only the attribute type DC, can be mapped back into domain
   names. Note that this document does not define a domain name
   equivalence for any other distinguished names.

4. Attribute Type Definition

   The DC (short for domainComponent) attribute type is defined as
   follows:

    ( 0.9.2342.19200300.100.1.25 NAME 'dc' EQUALITY caseIgnoreIA5Match
     SUBSTR caseIgnoreIA5SubstringsMatch
     SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 SINGLE-VALUE )
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