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Versions: 00 01 02 03 04 05 RFC 3674

INTERNET-DRAFT                                      Kurt D. Zeilenga
Intended Category: Standard Track                   OpenLDAP Foundation
Expires in six months                               26 May 2003

                        Feature Discovery in LDAP

Status of this Memo

  This document is an Internet-Draft and is in full conformance with all
  provisions of Section 10 of RFC2026.

  This document is intended to be, after appropriate review and
  revision, submitted to the RFC Editor as an Standard Track document.
  Distribution of this memo is unlimited.  Technical discussion of this
  document will take place on the IETF LDAP Extension Working Group
  mailing list <ldapext@ietf.org>.  Please send editorial comments
  directly to the author <Kurt@OpenLDAP.org>.

  Internet-Drafts are working documents of the Internet Engineering Task
  Force (IETF), its areas, and its working groups.  Note that other
  groups may also distribute working documents as Internet-Drafts.
  Internet-Drafts are draft documents valid for a maximum of six months
  and may be updated, replaced, or obsoleted by other documents at any
  time.  It is inappropriate to use Internet-Drafts as reference
  material or to cite them other than as ``work in progress.''

  The list of current Internet-Drafts can be accessed at
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  Copyright (C) The Internet Society (2003).  All Rights Reserved.

  Please see the Full Copyright section near the end of this document
  for more information.


  The Lightweight Directory Access Protocol (LDAP) is an extensible
  protocol with numerous elective features.  This document introduces a
  general mechanism for discovery of elective features and extensions
  which cannot be discovered using existing mechanisms.

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1. Background and Intended Use

  The Lightweight Directory Access Protocol (LDAP) [RFC3377] is an
  extensible protocol with numerous elective features.  LDAP provides
  mechanisms for a client to discover supported protocol versions,
  controls, extended operations, Simple Authentication and Security
  Layer (SASL) mechanisms, and subschema information.  However, these
  mechanisms are not designed to support general feature discovery.

  This document describes a simple, general-purpose mechanism which
  clients may use to discover the set of elective features supported by
  a server.  For example, this mechanism could be used by a client to
  discover whether or not the server supports requests for all
  operational attributes, e.g. "+" [OPATTRS].  As another example, this
  mechanism could be used to discover absolute true, e.g. "(&)" and
  false, e.g. "(|)", search filters [T-F] support.

  This document extends the LDAP Protocol Mechanism registry [RFC3383]
  to support registration of values of the supportedFeatures attribute.
  This registry is managed by the Internet Assigned Numbers Authority

  Schema definitions are provided using LDAP description formats
  [RFC2252].  Definitions provided here are formatted (line wrapped) for

  The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
  document are to be interpreted as described in BCP 14 [RFC2119].

2. Discovery of supported features

  Each elective feature whose support may be discovered SHALL be
  identified by an Object Identifier (OID).  A server advertises its
  support for a given feature by providing the OID associated with the
  feature as a value of the 'supportedFeatures' attribute held in the
  root DSE.  A client may examine the values of this attribute to
  determine if a particular feature is supported by the server.  A
  client MUST ignore values it doesn't recognize as they refer to
  elective features it doesn't implement.

  Features associated with Standard Track protocol mechanisms MUST be
  registered.  Features associated with other protocol mechanisms SHOULD
  be registered.  Procedures for registering protocol mechanisms are are
  described in [RFC3383].  "Feature" should be placed in the usage field
  of the submitted LDAP Protocol Mechanism template.

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  The 'supportedFeatures' attribute type is described as follows:

        NAME 'supportedFeatures'
        DESC 'features supported by the server'
        EQUALITY objectIdentifierMatch
        USAGE dSAOperation )

  Servers MUST be capable of recognizing this attribute type by the name
  'supportedFeatures'.  Servers MAY recognize the attribute type by
  other names.

4. Security Considerations

  As rogue clients can discover features of a server by other means
  (such as by trial and error), this feature discovery mechanism is not
  believed to introduce any new security risk to LDAP.

5. IANA Considerations

5.1. Registration of Features as Protocol Mechanisms

  Future specifications detailing LDAP features are to register each
  feature as a LDAP Protocol Mechanism per guidance given in BCP 64
  [RFC3383].  A usage of "Feature" in a Protocol Mechanism registration
  template indicates that the value to be registered is associated with
  an LDAP feature.

5.2. Registration of the supportedFeatures descriptor

  It is requested that IANA register upon Standards Action the LDAP
  'supportedFeatures' descriptor.  The following registration template
  is suggested:

      Subject: Request for LDAP Descriptor Registration
      Descriptor (short name): supportedFeatures
      Object Identifier:
      Person & email address to contact for further information:
          Kurt Zeilenga <kurt@OpenLDAP.org>
      Usage: Attribute Type
      Specification: RFC XXXX
      Author/Change Controller: IESG

  This OID was assigned [ASSIGN] by OpenLDAP Foundation under its IANA

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  assigned private enterprise allocation [PRIVATE] for use in this

6. Acknowledgment

  This document is based upon input from the IETF LDAPEXT working group.

7. Author's Address

  Kurt D. Zeilenga
  OpenLDAP Foundation

8. Normative References

  [RFC2119]     Bradner, S., "Key words for use in RFCs to Indicate
                Requirement Levels", BCP 14 (also RFC 2119), March 1997.

  [RFC2252]     Wahl, M., A. Coulbeck, T. Howes, and S. Kille,
                "Lightweight Directory Access Protocol (v3):  Attribute
                Syntax Definitions", RFC 2252, December 1997.

  [RFC3377]     Hodges, J. and R. Morgan, "Lightweight Directory Access
                Protocol (v3): Technical Specification", RFC 3377,
                September 2002.

  [RFC3383]     Zeilenga, K., "IANA Considerations for LDAP", BCP 64
                (also RFC 3383), September 2002.

9. Informative References

  [OPATTRS]     Zeilenga, K., "LDAPv3: All Operational Attributes",
                draft-zeilenga-ldap-opattrs-xx.txt, a work in progress.

  [T-F]         Zeilenga, K., "LDAP True/False Filters",
                draft-zeilenga-ldap-t-f-xx.txt, a work in progress.

  [ASSIGN]      OpenLDAP Foundation, "OpenLDAP OID Delegations",

  [PRIVATE]     IANA, "Private Enterprise Numbers",

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Intellectual Property Rights

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Full Copyright

  Copyright (C) The Internet Society (2003). All Rights Reserved.

  This document and translations of it may be copied and furnished to
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  or as required to translate it into languages other than English.

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