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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
+
+
+
+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.
+
+      - a space (' ' U+0020) or number sign ('#' U+0023) occurring at
+        the beginning of the string;
+
+      - a space (' ' U+0020) character occurring at the end of the
+        string;
+
+
+
+
+
+
+Zeilenga                    Standards Track                     [Page 4]
+
+RFC 4514               LDAP: Distinguished Names               June 2006
+
+
+      - one of the characters '"', '+', ',', ';', '<', '>',  or '\'
+        (U+0022, U+002B, U+002C, U+003B, U+003C, U+003E, or U+005C,
+        respectively);
+
+      - 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:
+
+      - the common name of the object (i.e., a person's full name)
+      - an email or TCP/IP address
+      - its physical location (country, locality, city, street address)
+      - 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:
+
+      - Removed IESG Note.  The IESG Note has been addressed.
+      - Replaced all references to ISO 10646-1 with [Unicode].
+      - Clarified (in Section 1) that this document does not define a
+        canonical string representation.
+      - 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.
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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]
+