WDIFF

draft-zeilenga-ldap-features-04.txt --> draft-zeilenga-ldap-features-05.txt

INTERNET-DRAFT Kurt D. Zeilenga
Intended Category: Standard Track OpenLDAP Foundation
Expires in six months 4 August 2002 26 May 2003

Feature Discovery in LDAP
<draft-zeilenga-ldap-features-04.txt>
<draft-zeilenga-ldap-features-05.txt>

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>.

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

Abstract

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

LDAP [RFC2251]

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, SASL 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 request requests for all
operational attributes, e.g. "+" [OPATTRS]. As another example, this
mechanism could be used to discover absolete absolute true, e.g. "(&)" and
false, e.g. "(|)", search filters [T-F] support.

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

Schema definitions are provided using LDAPv3 LDAP description formats
[RFC2252]. Definitions provided here are formatted (line wrapped) for
readability.

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].

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 [LDAPIANA]. [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:

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( 1.3.6.1.4.1.4203.1.3.5
NAME 'supportedFeatures'
DESC 'features supported by the server'
EQUALITY objectIdentifierMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.38
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 detail detailing LDAP features are to be registered register each
feature as a LDAP Protocol Mechanisms Mechanism per guidance provided given in [LDAPIANA]. 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 supportedFeature 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: 1.3.6.1.4.1.4203.1.3.5
Person & email address to contact for further information:
Kurt Zeilenga <kurt@OpenLDAP.org>
Usage: Attribute Type
Specification: RFCXXXX 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
specification.

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6. Acknowledgment

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

7. Author's Address

Kurt D. Zeilenga
OpenLDAP Foundation
<Kurt@OpenLDAP.org>

8. Normative References

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

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

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

9. Informative References

[LDAPIANA] K.

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

[RFC3383] Zeilenga, K., "IANA Considerations for LDAP", draft-ietf-
ldapbis-iana-xx.txt, a work in progress. BCP 64
(also RFC 3383), September 2002.

9. Informative References

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

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

[ASSIGN] OpenLDAP Foundation, "OpenLDAP OID Delegations",
http://www.openldap.org/foundation/oid-delegate.txt.

[PRIVATE] IANA, "Private Enterprise Numbers",
http://www.iana.org/assignments/enterprise-numbers.

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