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rfc:rfc4514

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

Zeilenga Standards Track [Page 1] 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].

Zeilenga Standards Track [Page 2] 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
 [RFC3629] encoded Unicode [Unicode] character string representation.
 Other documents may describe other algorithms for converting a
 distinguished name to a string, but only strings that conform to the
 grammar defined in Section 3 SHALL be produced by LDAP
 implementations.

2.1. Converting the RDNSequence

 If the RDNSequence is an empty sequence, the result is the empty or
 zero-length string.
 Otherwise, the output consists of the string encodings of each
 RelativeDistinguishedName in the RDNSequence (according to Section
 2.2), starting with the last element of the sequence and moving
 backwards toward the first.
 The encodings of adjoining RelativeDistinguishedNames are separated
 by a comma (',' U+002C) character.

2.2. Converting RelativeDistinguishedName

 When converting from an ASN.1 RelativeDistinguishedName to a string,
 the output consists of the string encodings of each
 AttributeTypeAndValue (according to Section 2.3), in any order.
 Where there is a multi-valued RDN, the outputs from adjoining
 AttributeTypeAndValues are separated by a plus sign ('+' U+002B)
 character.

Zeilenga Standards Track [Page 3] RFC 4514 LDAP: Distinguished Names June 2006

2.3. Converting AttributeTypeAndValue

 The AttributeTypeAndValue is encoded as the string representation of
 the AttributeType, followed by an equals sign ('=' U+003D) character,
 followed by the string representation of the AttributeValue.  The
 encoding of the AttributeValue is given in Section 2.4.
 If the AttributeType is defined to have a short name (descriptor)
 [RFC4512] and that short name is known to be registered [REGISTRY]
 [RFC4520] as identifying the AttributeType, that short name, a
 <descr>, is used.  Otherwise the AttributeType is encoded as the
 dotted-decimal encoding, a <numericoid>, of its OBJECT IDENTIFIER.
 The <descr> and <numericoid> are defined in [RFC4512].
 Implementations are not expected to dynamically update their
 knowledge of registered short names.  However, implementations SHOULD
 provide a mechanism to allow their knowledge of registered short
 names to be updated.

2.4. Converting an AttributeValue from ASN.1 to a String

 If the AttributeType is of the dotted-decimal form, the
 AttributeValue is represented by an number sign ('#' U+0023)
 character followed by the hexadecimal encoding of each of the octets
 of the BER encoding of the X.500 AttributeValue.  This form is also
 used when the syntax of the AttributeValue does not have an LDAP-
 specific ([RFC4517], Section 3.1) string encoding defined for it, or
 the LDAP-specific string encoding is not restricted to UTF-8-encoded
 Unicode characters.  This form may also be used in other cases, such
 as when a reversible string representation is desired (see Section
 5.2).
 Otherwise, if the AttributeValue is of a syntax that has a LDAP-
 specific string encoding, the value is converted first to a UTF-8-
 encoded Unicode string according to its syntax specification (see
 [RFC4517], Section 3.3, for examples).  If that UTF-8-encoded Unicode
 string does not have any of the following characters that need
 escaping, then that string can be used as the string representation
 of the value.
  1. a space (' ' U+0020) or number sign ('#' U+0023) occurring at

the beginning of the string;

  1. a space (' ' U+0020) character occurring at the end of the

string;

Zeilenga Standards Track [Page 4] RFC 4514 LDAP: Distinguished Names June 2006

  1. one of the characters '"', '+', ',', ';', '<', '>', or '\'

(U+0022, U+002B, U+002C, U+003B, U+003C, U+003E, or U+005C,

      respectively);
  1. the null (U+0000) character.
 Other characters may be escaped.
 Each octet of the character to be escaped is replaced by a backslash
 and two hex digits, which form a single octet in the code of the
 character.  Alternatively, if and only if the character to be escaped
 is one of
    ' ', '"', '#', '+', ',', ';', '<', '=', '>', or '\'
    (U+0020, U+0022, U+0023, U+002B, U+002C, U+003B,
     U+003C, U+003D, U+003E, U+005C, respectively)
 it can be prefixed by a backslash ('\' U+005C).
 Examples of the escaping mechanism are shown in Section 4.

3. Parsing a String Back to a Distinguished Name

 The string representation of Distinguished Names is restricted to
 UTF-8 [RFC3629] encoded Unicode [Unicode] characters.  The structure
 of this string representation is specified using the following
 Augmented BNF [RFC4234] grammar:
    distinguishedName = [ relativeDistinguishedName
        *( COMMA relativeDistinguishedName ) ]
    relativeDistinguishedName = attributeTypeAndValue
        *( PLUS attributeTypeAndValue )
    attributeTypeAndValue = attributeType EQUALS attributeValue
    attributeType = descr / numericoid
    attributeValue = string / hexstring
    ; The following characters are to be escaped when they appear
    ; in the value to be encoded: ESC, one of <escaped>, leading
    ; SHARP or SPACE, trailing SPACE, and NULL.
    string =   [ ( leadchar / pair ) [ *( stringchar / pair )
       ( trailchar / pair ) ] ]
    leadchar = LUTF1 / UTFMB
    LUTF1 = %x01-1F / %x21 / %x24-2A / %x2D-3A /
       %x3D / %x3F-5B / %x5D-7F
    trailchar  = TUTF1 / UTFMB
    TUTF1 = %x01-1F / %x21 / %x23-2A / %x2D-3A /

Zeilenga Standards Track [Page 5] RFC 4514 LDAP: Distinguished Names June 2006

       %x3D / %x3F-5B / %x5D-7F
    stringchar = SUTF1 / UTFMB
    SUTF1 = %x01-21 / %x23-2A / %x2D-3A /
       %x3D / %x3F-5B / %x5D-7F
    pair = ESC ( ESC / special / hexpair )
    special = escaped / SPACE / SHARP / EQUALS
    escaped = DQUOTE / PLUS / COMMA / SEMI / LANGLE / RANGLE
    hexstring = SHARP 1*hexpair
    hexpair = HEX HEX
 where the productions <descr>, <numericoid>, <COMMA>, <DQUOTE>,
 <EQUALS>, <ESC>, <HEX>, <LANGLE>, <NULL>, <PLUS>, <RANGLE>, <SEMI>,
 <SPACE>, <SHARP>, and <UTFMB> are defined in [RFC4512].
 Each <attributeType>, either a <descr> or a <numericoid>, refers to
 an attribute type of an attribute value assertion (AVA).  The
 <attributeType> is followed by an <EQUALS> and an <attributeValue>.
 The <attributeValue> is either in <string> or <hexstring> form.
 If in <string> form, a LDAP string representation asserted value can
 be obtained by replacing (left to right, non-recursively) each <pair>
 appearing in the <string> as follows:
    replace <ESC><ESC> with <ESC>;
    replace <ESC><special> with <special>;
    replace <ESC><hexpair> with the octet indicated by the <hexpair>.
 If in <hexstring> form, a BER representation can be obtained from
 converting each <hexpair> of the <hexstring> to the octet indicated
 by the <hexpair>.
 There is one or more attribute value assertions, separated by <PLUS>,
 for a relative distinguished name.
 There is zero or more relative distinguished names, separated by
 <COMMA>, for a distinguished name.
 Implementations MUST recognize AttributeType name strings
 (descriptors) listed in the following table, but MAY recognize other
 name strings.

Zeilenga Standards Track [Page 6] RFC 4514 LDAP: Distinguished Names June 2006

    String  X.500 AttributeType
    ------  --------------------------------------------
    CN      commonName (2.5.4.3)
    L       localityName (2.5.4.7)
    ST      stateOrProvinceName (2.5.4.8)
    O       organizationName (2.5.4.10)
    OU      organizationalUnitName (2.5.4.11)
    C       countryName (2.5.4.6)
    STREET  streetAddress (2.5.4.9)
    DC      domainComponent (0.9.2342.19200300.100.1.25)
    UID     userId (0.9.2342.19200300.100.1.1)
 These attribute types are described in [RFC4519].
 Implementations MAY recognize other DN string representations.
 However, as there is no requirement that alternative DN string
 representations be recognized (and, if so, how), implementations
 SHOULD only generate DN strings in accordance with Section 2 of this
 document.

4. Examples

 This notation is designed to be convenient for common forms of name.
 This section gives a few examples of distinguished names written
 using this notation.  First is a name containing three relative
 distinguished names (RDNs):
    UID=jsmith,DC=example,DC=net
 Here is an example of a name containing three RDNs, in which the
 first RDN is multi-valued:
    OU=Sales+CN=J.  Smith,DC=example,DC=net
 This example shows the method of escaping of a special characters
 appearing in a common name:
    CN=James \"Jim\" Smith\, III,DC=example,DC=net
 The following shows the method for encoding a value that contains a
 carriage return character:
    CN=Before\0dAfter,DC=example,DC=net
 In this RDN example, the type in the RDN is unrecognized, and the
 value is the BER encoding of an OCTET STRING containing two octets,
 0x48 and 0x69.

Zeilenga Standards Track [Page 7] RFC 4514 LDAP: Distinguished Names June 2006

    1.3.6.1.4.1.1466.0=#04024869
 Finally, this example shows an RDN whose commonName value consists of
 5 letters:
    Unicode Character                Code       UTF-8   Escaped
    -------------------------------  ------     ------  --------
    LATIN CAPITAL LETTER L           U+004C     0x4C    L
    LATIN SMALL LETTER U             U+0075     0x75    u
    LATIN SMALL LETTER C WITH CARON  U+010D     0xC48D  \C4\8D
    LATIN SMALL LETTER I             U+0069     0x69    i
    LATIN SMALL LETTER C WITH ACUTE  U+0107     0xC487  \C4\87
 This could be encoded in printable ASCII [ASCII] (useful for
 debugging purposes) as:
    CN=Lu\C4\8Di\C4\87

5. Security Considerations

 The following security considerations are specific to the handling of
 distinguished names.  LDAP security considerations are discussed in
 [RFC4511] and other documents comprising the LDAP Technical
 Specification [RFC4510].

5.1. Disclosure

 Distinguished Names typically consist of descriptive information
 about the entries they name, which can be people, organizations,
 devices, or other real-world objects.  This frequently includes some
 of the following kinds of information:
  1. the common name of the object (i.e., a person's full name)
  2. an email or TCP/IP address
  3. its physical location (country, locality, city, street address)
  4. organizational attributes (such as department name or

affiliation)

 In some cases, such information can be considered sensitive.  In many
 countries, privacy laws exist that prohibit disclosure of certain
 kinds of descriptive information (e.g., email addresses).  Hence,
 server implementers are encouraged to support Directory Information
 Tree (DIT) structural rules and name forms [RFC4512], as these
 provide a mechanism for administrators to select appropriate naming
 attributes for entries.  Administrators are encouraged to use
 mechanisms, access controls, and other administrative controls that
 may be available to restrict use of attributes containing sensitive
 information in naming of entries.   Additionally, use of

Zeilenga Standards Track [Page 8] RFC 4514 LDAP: Distinguished Names June 2006

 authentication and data security services in LDAP [RFC4513][RFC4511]
 should be considered.

5.2. Use of Distinguished Names in Security Applications

 The transformations of an AttributeValue value from its X.501 form to
 an LDAP string representation are not always reversible back to the
 same BER (Basic Encoding Rules) or DER (Distinguished Encoding Rules)
 form.  An example of a situation that requires the DER form of a
 distinguished name is the verification of an X.509 certificate.
 For example, a distinguished name consisting of one RDN with one AVA,
 in which the type is commonName and the value is of the TeletexString
 choice with the letters 'Sam', would be represented in LDAP as the
 string <CN=Sam>.  Another distinguished name in which the value is
 still 'Sam', but is of the PrintableString choice, would have the
 same representation <CN=Sam>.
 Applications that require the reconstruction of the DER form of the
 value SHOULD NOT use the string representation of attribute syntaxes
 when converting a distinguished name to the LDAP format.  Instead,
 they SHOULD use the hexadecimal form prefixed by the number sign ('#'
 U+0023) as described in the first paragraph of Section 2.4.

6. Acknowledgements

 This document is an update to RFC 2253, by Mark Wahl, Tim Howes, and
 Steve Kille.  RFC 2253 was a product of the IETF ASID Working Group.
 This document is a product of the IETF LDAPBIS Working Group.

7. References

7.1. Normative References

 [REGISTRY]    IANA, Object Identifier Descriptors Registry,
               <http://www.iana.org/assignments/ldap-parameters>.
 [Unicode]     The Unicode Consortium, "The Unicode Standard, Version
               3.2.0" is defined by "The Unicode Standard, Version
               3.0" (Reading, MA, Addison-Wesley, 2000.  ISBN 0-201-
               61633-5), as amended by the "Unicode Standard Annex
               #27: Unicode 3.1"
               (http://www.unicode.org/reports/tr27/) and by the
               "Unicode Standard Annex #28: Unicode 3.2"
               (http://www.unicode.org/reports/tr28/).

Zeilenga Standards Track [Page 9] RFC 4514 LDAP: Distinguished Names June 2006

 [X.501]       International Telecommunication Union -
               Telecommunication Standardization Sector, "The
               Directory -- Models," X.501(1993) (also ISO/IEC 9594-
               2:1994).
 [X.680]       International Telecommunication Union -
               Telecommunication Standardization Sector, "Abstract
               Syntax Notation One (ASN.1) - Specification of Basic
               Notation", X.680(1997) (also ISO/IEC 8824-1:1998).
 [RFC2119]     Bradner, S., "Key words for use in RFCs to Indicate
               Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC3629]     Yergeau, F., "UTF-8, a transformation format of ISO
               10646", STD 63, RFC 3629, November 2003.
 [RFC4234]     Crocker, D. and P. Overell, "Augmented BNF for Syntax
               Specifications: ABNF", RFC 4234, October 2005.
 [RFC4510]     Zeilenga, K., Ed., "Lightweight Directory Access
               Protocol (LDAP): Technical Specification Road Map", RFC
               4510, June 2006.
 [RFC4511]     Sermersheim, J., Ed., "Lightweight Directory Access
               Protocol (LDAP): The Protocol", RFC 4511, June 2006.
 [RFC4512]     Zeilenga, K., "Lightweight Directory Access Protocol
               (LDAP): Directory Information Models", RFC 4512, June
               2006.
 [RFC4513]     Harrison, R., Ed., "Lightweight Directory Access
               Protocol (LDAP): Authentication Methods and Security
               Mechanisms", RFC 4513, June 2006.
 [RFC4517]     Legg, S., Ed., "Lightweight Directory Access Protocol
               (LDAP): Syntaxes and Matching Rules", RFC 4517, June
               2006.
 [RFC4519]     Sciberras, A., Ed., "Lightweight Directory Access
               Protocol (LDAP): Schema for User Applications", RFC
               4519, June 2006.
 [RFC4520]     Zeilenga, K., "Internet Assigned Numbers Authority
               (IANA) Considerations for the Lightweight Directory
               Access Protocol (LDAP)", BCP 64, RFC 4520, June 2006.

Zeilenga Standards Track [Page 10] RFC 4514 LDAP: Distinguished Names June 2006

7.2. Informative References

 [ASCII]       Coded Character Set--7-bit American Standard Code for
               Information Interchange, ANSI X3.4-1986.
 [CharModel]   Whistler, K. and M. Davis, "Unicode Technical Report
               #17, Character Encoding Model", UTR17,
               <http://www.unicode.org/unicode/reports/tr17/>, August
               2000.
 [Glossary]    The Unicode Consortium, "Unicode Glossary",
               <http://www.unicode.org/glossary/>.
 [X.500]       International Telecommunication Union -
               Telecommunication Standardization Sector, "The
               Directory -- Overview of concepts, models and
               services," X.500(1993) (also ISO/IEC 9594-1:1994).
 [X.511]       International Telecommunication Union -
               Telecommunication Standardization Sector, "The
               Directory: Abstract Service Definition", X.511(1993)
               (also ISO/IEC 9594-3:1993).
 [X.690]       International Telecommunication Union -
               Telecommunication Standardization Sector,
               "Specification of ASN.1 encoding rules: Basic Encoding
               Rules (BER), Canonical Encoding Rules (CER), and
               Distinguished Encoding Rules (DER)", X.690(1997) (also
               ISO/IEC 8825-1:1998).
 [RFC2849]     Good, G., "The LDAP Data Interchange Format (LDIF) -
               Technical Specification", RFC 2849, June 2000.

Zeilenga Standards Track [Page 11] RFC 4514 LDAP: Distinguished Names June 2006

Appendix A. Presentation Issues

 This appendix is provided for informational purposes only; it is not
 a normative part of this specification.
 The string representation described in this document is not intended
 to be presented to humans without translation.  However, at times it
 may be desirable to present non-translated DN strings to users.  This
 section discusses presentation issues associated with non-translated
 DN strings.  Issues with presentation of translated DN strings are
 not discussed in this appendix.  Transcoding issues are also not
 discussed in this appendix.
 This appendix provides guidance for applications presenting DN
 strings to users.  This section is not comprehensive; it does not
 discuss all presentation issues that implementers may face.
 Not all user interfaces are capable of displaying the full set of
 Unicode characters.  Some Unicode characters are not displayable.
 It is recommended that human interfaces use the optional hex pair
 escaping mechanism (Section 2.3) to produce a string representation
 suitable for display to the user.  For example, an application can
 generate a DN string for display that escapes all non-printable
 characters appearing in the AttributeValue's string representation
 (as demonstrated in the final example of Section 4).
 When a DN string is displayed in free-form text, it is often
 necessary to distinguish the DN string from surrounding text.  While
 this is often done with whitespace (as demonstrated in Section 4), it
 is noted that DN strings may end with whitespace.  Careful readers of
 Section 3 will note that the characters '<' (U+003C) and '>' (U+003E)
 may only appear in the DN string if escaped.  These characters are
 intended to be used in free-form text to distinguish a DN string from
 surrounding text.  For example, <CN=Sam\ > distinguishes the string
 representation of the DN composed of one RDN consisting of the AVA
 (the commonName (CN) value 'Sam ') from the surrounding text.  It
 should be noted to the user that the wrapping '<' and '>' characters
 are not part of the DN string.
 DN strings can be quite long.  It is often desirable to line-wrap
 overly long DN strings in presentations.  Line wrapping should be
 done by inserting whitespace after the RDN separator character or, if
 necessary, after the AVA separator character.  It should be noted to
 the user that the inserted whitespace is not part of the DN string
 and is to be removed before use in LDAP.  For example, the following
 DN string is long:

Zeilenga Standards Track [Page 12] RFC 4514 LDAP: Distinguished Names June 2006

       CN=Kurt D.  Zeilenga,OU=Engineering,L=Redwood Shores,
       O=OpenLDAP Foundation,ST=California,C=US
 So it has been line-wrapped for readability.  The extra whitespace is
 to be removed before the DN string is used in LDAP.
 Inserting whitespace is not advised because it may not be obvious to
 the user which whitespace is part of the DN string and which
 whitespace was added for readability.
 Another alternative is to use the LDAP Data Interchange Format (LDIF)
 [RFC2849].  For example:
       # This entry has a long DN...
       dn: CN=Kurt D.  Zeilenga,OU=Engineering,L=Redwood Shores,
        O=OpenLDAP Foundation,ST=California,C=US
       CN: Kurt D.  Zeilenga
       SN: Zeilenga
       objectClass: person

Appendix B. Changes Made since RFC 2253

 This appendix is provided for informational purposes only, it is not
 a normative part of this specification.
 The following substantive changes were made to RFC 2253:
  1. Removed IESG Note. The IESG Note has been addressed.
  2. Replaced all references to ISO 10646-1 with [Unicode].
  3. Clarified (in Section 1) that this document does not define a

canonical string representation.

  1. Clarified that Section 2 describes the RECOMMENDED encoding

algorithm and that alternative algorithms are allowed. Some

      encoding options described in RFC 2253 are now treated as
      alternative algorithms in this specification.
    - Revised specification (in Section 2) to allow short names of any
      registered attribute type to appear in string representations of
      DNs instead of being restricted to a "published table".  Removed
      "as an example" language.  Added statement (in Section 3)
      allowing recognition of additional names but require recognition
      of those names in the published table.  The table now appears in
      Section 3.
    - Removed specification of additional requirements for LDAPv2
      implementations which also support LDAPv3 (RFC 2253, Section 4)
      as LDAPv2 is now Historic.
    - Allowed recognition of alternative string representations.
    - Updated Section 2.4 to allow hex pair escaping of all characters
      and clarified escaping for when multiple octet UTF-8 encodings

Zeilenga Standards Track [Page 13] RFC 4514 LDAP: Distinguished Names June 2006

      are present.  Indicated that null (U+0000) character is to be
      escaped.  Indicated that equals sign ('=' U+003D) character may
      be escaped as '\='.
    - Rewrote Section 3 to use ABNF as defined in RFC 4234.
    - Updated the Section 3 ABNF.  Changes include:
      + allowed AttributeType short names of length 1 (e.g., 'L'),
      + used more restrictive <oid> production in AttributeTypes,
      + did not require escaping of equals sign ('=' U+003D)
        characters,
      + did not require escaping of non-leading number sign ('#'
        U+0023) characters,
      + allowed space (' ' U+0020) to be escaped as '\ ',
      + required hex escaping of null (U+0000) characters, and
      + removed LDAPv2-only constructs.
    - Updated Section 3 to describe how to parse elements of the
      grammar.
    - Rewrote examples.
    - Added reference to documentations containing general LDAP
      security considerations.
    - Added discussion of presentation issues (Appendix A).
    - Added this appendix.
 In addition, numerous editorial changes were made.

Editor's Address

 Kurt D.  Zeilenga
 OpenLDAP Foundation
 EMail: Kurt@OpenLDAP.org

Zeilenga Standards Track [Page 14] RFC 4514 LDAP: Distinguished Names June 2006

Full Copyright Statement

 Copyright (C) The Internet Society (2006).
 This document is subject to the rights, licenses and restrictions
 contained in BCP 78, and except as set forth therein, the authors
 retain all their rights.
 This document and the information contained herein are provided on an
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 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
 ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
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 INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
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Acknowledgement

 Funding for the RFC Editor function is provided by the IETF
 Administrative Support Activity (IASA).

Zeilenga Standards Track [Page 15]

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