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 . Please send editorial comments directly to the author . 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 . The list of Internet-Draft Shadow Directories can be accessed at . Copyright (C) The Internet Society (2003). All Rights Reserved. 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. Zeilenga draft-zeilenga-ldap-features-05 [Page 1] INTERNET-DRAFT LDAP supportedFeatures 26 May 2003 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 (IANA). Schema definitions are provided using 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 [RFC3383]. "Feature" should be placed in the usage field of the submitted LDAP Protocol Mechanism template. Zeilenga draft-zeilenga-ldap-features-05 [Page 2] INTERNET-DRAFT LDAP supportedFeatures 26 May 2003 The 'supportedFeatures' attribute type is described as follows: ( 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 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: 1.3.6.1.4.1.4203.1.3.5 Person & email address to contact for further information: Kurt Zeilenga Usage: Attribute Type Specification: RFC XXXX Author/Change Controller: IESG This OID was assigned [ASSIGN] by OpenLDAP Foundation under its IANA Zeilenga draft-zeilenga-ldap-features-05 [Page 3] INTERNET-DRAFT LDAP supportedFeatures 26 May 2003 assigned private enterprise allocation [PRIVATE] for use in this specification. 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", http://www.openldap.org/foundation/oid-delegate.txt. [PRIVATE] IANA, "Private Enterprise Numbers", http://www.iana.org/assignments/enterprise-numbers. Zeilenga draft-zeilenga-ldap-features-05 [Page 4] INTERNET-DRAFT LDAP supportedFeatures 26 May 2003 Intellectual Property Rights The IETF takes no position regarding the validity or scope of any intellectual property or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; neither does it represent that it has made any effort to identify any such rights. Information on the IETF's procedures with respect to rights in standards-track and standards-related documentation can be found in BCP-11. Copies of claims of rights made available for publication and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementors or users of this specification can be obtained from the IETF Secretariat. 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However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. Zeilenga draft-zeilenga-ldap-features-05 [Page 5]