Network Working Group J;. Sermersheim
Internet-Draft Novell, Inc
Updates: 2251 (if approved) July 2004
Expires: December 30, 2004
Subordinate Subtree Search Scope for LDAP
draft-sermersheim-ldap-subordinate-scope-00.txt
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Copyright Notice
Copyright (C) The Internet Society (2004).
Abstract
The Lightweight Directory Application 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.
Discussion Forum
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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 subordinateSubtrees cope 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 4.
A DSA which receives and supports the subordinateSubtree
SearchRequest.scope constrains the search scope to all subordinate
objects.
A DSA which receives but does not support the subordinateSubtree
SearchRequest.scope returns a protocolError resultCode in the
SearchResultDone.
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 "subord" 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.
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3.1 Application to LDAP URL <scope>
A new <scope> value of "subord" is added. Using the <scope> type
from LDAP URL [RFC2255], the ABNF is as follows:
scope /= "subord"
Implementations processing but which do not understand or support the
"subord" <scope> of an LDAP URL raise an appropriate error.
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 'subordScope', and the
exvalue is omitted. The extension may be marked as either critical
or non-critical.
If supported, the subordScope extension overrides any value set in
the <scope> field.
4. DSA Advertisement of support
A DSA may advertise its support of the subordinateSubtree item in the
SearchRequest.scope by inclusion of IANA-ASSIGNED-OID.2 in the
'supportedFeatures' attribute of the root DSE.
5. 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.
6 Normative References
[RFC2251] Wahl, M., Howes, T. and S. Kille, "Lightweight Directory
Access Protocol (v3)", RFC 2251, December 1997.
[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)
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Considerations for the Lightweight Directory Access
Protocol (LDAP)", BCP 64, RFC 3383, September 2002.
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 subordScope LDAP URL extension
IANA-ASSIGNED-OID.2 subordinateScope Supported Feature
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: subordScope LDAP URL extension
Person & email address to contact for further information:
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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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