Lightweight Directory Access Protocol (LDAP): String Representation of Distinguished Names
RFC 4514

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Network Working Group                                   K. Zeilenga, Ed.
Request for Comments: 4514                           OpenLDAP Foundation
Obsoletes: 2253                                                June 2006
Category: Standards Track

             Lightweight Directory Access Protocol (LDAP):
              String Representation of 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 (2006).

Abstract

   The X.500 Directory uses distinguished names (DNs) as primary keys to
   entries in the directory.  This document defines the string
   representation used in the Lightweight Directory Access Protocol
   (LDAP) to transfer distinguished names.  The string representation is
   designed to give a clean representation of commonly used
   distinguished names, while being able to represent any distinguished
   name.

1.  Background and Intended Usage

   In X.500-based directory systems [X.500], including those accessed
   using the Lightweight Directory Access Protocol (LDAP) [RFC4510],
   distinguished names (DNs) are used to unambiguously refer to
   directory entries [X.501][RFC4512].

   The structure of a DN [X.501] is described in terms of ASN.1 [X.680].
   In the X.500 Directory Access Protocol [X.511] (and other ITU-defined
   directory protocols), DNs are encoded using the Basic Encoding Rules
   (BER) [X.690].  In LDAP, DNs are represented in the string form
   described in this document.

   It is important to have a common format to be able to unambiguously
   represent a distinguished name.  The primary goal of this
   specification is ease of encoding and decoding.  A secondary goal is
   to have names that are human readable.  It is not expected that LDAP

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RFC 4514               LDAP: Distinguished Names               June 2006

   implementations with a human user interface would display these
   strings directly to the user, but that they would most likely be
   performing translations (such as expressing attribute type names in
   the local national language).

   This document defines the string representation of Distinguished
   Names used in LDAP [RFC4511][RFC4517].  Section 2 details the
   RECOMMENDED algorithm for converting a DN from its ASN.1 structured
   representation to a string.  Section 3 details how to convert a DN
   from a string to an ASN.1 structured representation.

   While other documents may define other algorithms for converting a DN
   from its ASN.1 structured representation to a string, all algorithms
   MUST produce strings that adhere to the requirements of Section 3.

   This document does not define a canonical string representation for
   DNs.  Comparison of DNs for equality is to be performed in accordance
   with the distinguishedNameMatch matching rule [RFC4517].

   This document is a integral part of the LDAP technical specification
   [RFC4510], which obsoletes the previously defined LDAP technical
   specification, RFC 3377, in its entirety.  This document obsoletes
   RFC 2253.  Changes since RFC 2253 are summarized in Appendix B.

   This specification assumes familiarity with X.500 [X.500] and the
   concept of Distinguished Name [X.501][RFC4512].

1.1.  Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in BCP 14 [RFC2119].

   Character names in this document use the notation for code points and
   names from the Unicode Standard [Unicode].  For example, the letter
   "a" may be represented as either <U+0061> or <LATIN SMALL LETTER A>.

   Note: a glossary of terms used in Unicode can be found in [Glossary].
   Information on the Unicode character encoding model can be found in
   [CharModel].

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RFC 4514               LDAP: Distinguished Names               June 2006

2.  Converting DistinguishedName from ASN.1 to a String

   X.501 [X.501] defines the ASN.1 [X.680] structure of distinguished
   name.  The following is a variant provided for discussion purposes.

      DistinguishedName ::= RDNSequence

      RDNSequence ::= SEQUENCE OF RelativeDistinguishedName

      RelativeDistinguishedName ::= SET SIZE (1..MAX) OF
          AttributeTypeAndValue

      AttributeTypeAndValue ::= SEQUENCE {
          type  AttributeType,
          value AttributeValue }

   This section defines the RECOMMENDED algorithm for converting a
   distinguished name from an ASN.1-structured representation to a UTF-8