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Network Working Group                                     J. Sermersheim
Internet-Draft                                               Novell, Inc
Updates: 2251 (if approved)                                 October 2004
Expires: April 4, 2005


               Subordinate Subtree Search Scope for LDAP
            draft-sermersheim-ldap-subordinate-scope-02.txt

Status of this Memo

   This document is an Internet-Draft and is subject to all provisions
   of Section 3 of RFC 3667.  By submitting this Internet-Draft, each
   author represents that any applicable patent or other IPR claims of
   which he or she is aware have been or will be disclosed, and any of
   which he or she become aware will be disclosed, in accordance with
   RFC 3668.

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   This Internet-Draft will expire on April 4, 2005.

Copyright Notice

   Copyright (C) The Internet Society (2004).

Abstract

   The Lightweight Directory Access Protocol (LDAP) specification
   supports three scope values for the search operation -- namely:
   baseObject, singleLevel, and wholeSubtree.  This document introduces
   a subordinateSubtree scope which constrains the search scope to all
   subordinates of the named base object.




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Discussion Forum

   Technical discussion of this document will take place on the IETF
   LDAP Extensions mailing list <ldapext@ietf.org>.  Please send
   editorial comments directly to the author.

1.  Overview

   There are a number of reasons which have surfaced for introducing a
   Lightweight Directory Application Protocol (LDAP) [RFC3377]
   SearchRequest.scope [RFC2251] which constrains the search scope to
   all subordinates of the named base object, and does not include the
   base object (as wholeSubtree does).  These reasons range from the
   obvious utility of allowing an LDAP client application the ability to
   exclude the base object from a wholeSubtree search scope, to
   distributed operation applications which require this scope for
   progressing search sub-operations resulting from an nssr DSE type
   reference.

   To meet these needs, the subordinateSubtree scope value is
   introduced.

   The subordinateSubtree scope is applied to the SearchRequest.scope
   field, the <scope> type and alternately the <extension> type of the
   LDAP URL [RFC2255] and may be applied to other specifications which
   include an LDAP search scope.  A mechanism is also given which allows
   LDAP Directory Server Agents (DSA)s to advertise support of this
   search scope.

2.  Application to SearchRequest.scope

   A new item is added to this ENUMERATED type.  The identifier is
   subordinateSubtree and the number is 3.

   A DSA which receives and supports the subordinateSubtree
   SearchRequest.scope constrains the search scope to all subordinate
   objects.

   As specified in [RFC2251] a DSA which receives but does not support
   the subordinateSubtree SearchRequest.scope returns a protocolError
   resultCode in the SearchResultDone.

2.1  Advertisement and discovery of support

   Servers supporting this feature SHOULD publish the object identifier
   IANA-ASSIGNED-OID.2 as a value of the 'supportedFeatures' [RFC3674]
   attribute in the root DSE.  Clients supporting this feature SHOULD
   NOT use the feature unless they have knowledge the server supports



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   it.

3.  LDAP URL applications

   The LDAP URL [RFC2255] specification allows the conveyance of a
   search scope.  This section intoduces two ways in which the
   subordinateScope search scope may be conveyed in an LDAP URL.  One
   way is by allowing a new "subordinates" scope in the <scope> part.
   Another way is through the introduction of an LDAP URL extension.
   The LDAP URL extension method is preferred for its criticality
   semantics.

3.1  Application to LDAP URL <scope>

   A new <scope> value of "subordinates" is added.  Using the <scope>
   type from LDAP URL [RFC2255], the ABNF is as follows:

   scope /= "subordinates"

   Implementations processing but which do not understand or support the
   "subordinates" <scope> of an LDAP URL raise an appropriate error.

   Servers MUST NOT return this scope value without knowledge that the
   client supports it.

3.2  Application to LDAP URL <extension>

   An LDAP URL <extension> mechanism is introduced here.  The <extype>
   is IANA-ASSIGNED-OID.1 or the descriptor 'subordinateScope', and the
   exvalue is omitted.  The extension may be marked as either critical
   or non-critical.

   If supported, the subordinateScope extension overrides any value set
   in the <scope> field.

4.  Security Considerations

   This specification introduces no security concerns above any
   associated with the existing wholeSubtree search scope value.

   As with the wholeSubtree search scope, this scope specifies that a
   search be applied to an entire subtree hierarchy.  Implementations
   should be aware of the relative cost of using or allowing this scope.

5.  Normative References

   [RFC2251]  Wahl, M., Howes, T. and S. Kille, "Lightweight Directory
              Access Protocol (v3)", RFC 2251, December 1997.



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   [RFC2255]  Howes, T. and M. Smith, "The LDAP URL Format", RFC 2255,
              December 1997.

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

   [RFC3383]  Zeilenga, K., "Internet Assigned Numbers Authority (IANA)
              Considerations for the Lightweight Directory Access
              Protocol (LDAP)", BCP 64, RFC 3383, September 2002.

   [RFC3674]  Zeilenga, K., "Feature Discovery in Lightweight Directory
              Access Protocol (LDAP)", RFC 3674, December 2003.


Author's Address

   Jim Sermersheim
   Novell, Inc
   1800 South Novell Place
   Provo, Utah  84606
   USA

   Phone: +1 801 861-3088
   Email: jimse@novell.com

Appendix A.  IANA Considerations

   Registration of the following values is requested [RFC3383].

A.1  LDAP Object Identifier Registrations

   It is requested that IANA register upon Standards Action an LDAP
   Object Identifier in identifying the protocol elements defined in
   this technical specification.  The following registration template is
   provided:

      Subject: Request for LDAP OID Registration
      Person & email address to contact for further information:
         Jim Sermersheim
         jimse@novell.com
      Specification: RFCXXXX
      Author/Change Controller: IESG
      Comments:
      2 delegations will be made under the assigned OID:
         IANA-ASSIGNED-OID.1 subordinateScope LDAP URL extension
         IANA-ASSIGNED-OID.2 subordinateScope Supported Feature




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A.2  LDAP Protocol Mechanism Registrations

   It is requested that IANA register upon Standards Action the LDAP
   protocol mechanism described in this document.  The following
   registration templates are given:

      Subject: Request for LDAP Protocol Mechanism Registration
      Object Identifier: IANA-ASSIGNED-OID.1
      Description: subordinateScope LDAP URL extension
      Person & email address to contact for further information:
         Jim Sermersheim
         jimse@novell.com
      Usage: Extension
      Specification: RFCXXXX
      Author/Change Controller: IESG
      Comments: none

A.3  LDAP Descriptor Registrations

   It is requested that IANA register upon Standards Action the LDAP
   descriptors described in this document.  The following registration
   templates are given:

      Subject: Request for LDAP Descriptor Registration
      Descriptor (short name): subordScope
      Object Identifier: IANA-ASSIGNED-OID.1
      Person & email address to contact for further information:
         Jim Sermersheim
         jimse@novell.com
      Usage: URL Extension
      Specification: RFCXXXX
      Author/Change Controller: IESG
      Comments: none


















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Acknowledgment

   Funding for the RFC Editor function is currently provided by the
   Internet Society.




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