INTERNET-DRAFT Kurt D. Zeilenga Intended Category: Standard Track OpenLDAP Foundation Expires in six months 5 March 2006 LDAP Transactions Status of Memo This document is intended to be, after appropriate review and revision, submitted to the IESG for consideration as a Proposed Standard. Distribution of this memo is unlimited. Technical discussion of this document will take place on the IETF LDAP Extensions mailing list . Please send editorial comments directly to the author . 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 becomes aware will be disclosed, in accordance with Section 6 of BCP 79. 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 http://www.ietf.org/1id-abstracts.html The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html Copyright (C) The Internet Society (2006). All Rights Reserved. Please see the Full Copyright section near the end of this document for more information. Abstract Lightweight Directory Access Protocol (LDAP) update operations, such Zeilenga LDAP Transactions [Page 1] INTERNET-DRAFT draft-zeilenga-ldap-txn-07 5 March 2006 as Add, Delete, and Modify operations, have atomic, consistency, isolation, durability (ACID) properties. Each of these update operations act upon an entry. However, It is often desirable to update two or more entries in a single unit of interaction, a transaction. Transactions are necessary to support a number of applications including resource provisioning and information replication. This document defines an LDAP extension to support transactions. 1. Overview This document extends the Lightweight Directory Access Protocol (LDAP) [Roadmap] to allow clients to group a number of related update operations [Protocol] and have them preformed as one unit of interaction, a transaction. As with distinct update operations, each transaction has atomic, consistency, isolation, and durability ([ACID]) properties. This extension consists of two extended operations, one control, and one unsolicited notification message. The Start Transaction operation is used to obtain a transaction identifier. This identifier is then attached to multiple update operations to indicate that they belong to transaction using the Transaction Specification control. The End Transaction is used to settle (commit or abort) the transaction. The Aborted Tranaction Notice is used notify the client the server is no longer willing or able to process an outstanding transaction. 1.1. Conventions and Terminology 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]. Protocol elements are described using ASN.1 [X.680] with implicit tags. The term "BER-encoded" means the element is to be encoded using the Basic Encoding Rules [X.690] under the restrictions detailed in Section 5.2 of [Protocol]. DSA stands for "Directory System Agent" (a server). DSE stands for "DSA-specific entry". 2. Elements of an LDAP Transaction 2.1. Start Transaction Request and Response Zeilenga LDAP Transactions [Page 2] INTERNET-DRAFT draft-zeilenga-ldap-txn-07 5 March 2006 A Start Transaction Request is an LDAPMessage of CHOICE extendedReq where the requestName is IANA-ASSIGNED-OID.1 and the requestValue is absent. A Start Transaction Response is an LDAPMessage of CHOICE extendedRes sent in response to a Start Transaction Request. Its responesName is absent. When the resultCode is success, responseValue is present and contains a transaction identifier. Otherwise, the responseValue is absent. 2.2. Transaction Specification Control A Transaction Specification Control is an LDAPControl where the controlType is IANA-ASSIGNED-OID.2, the criticality is TRUE, and the controlValue is a transaction identifer. The control is appropriate for update requests including Add, Delete, Modify, and ModifyDN requests [Protocol]. 2.3. End Transactions Request and Response An End Transaction Request is an LDAPMessage of CHOICE extendedReq where the requestName is IANA-ASSIGNED-OID.3 and the requestValue is present and contains a BER-encoded settlementValue. settlementValue ::= SEQUENCE { commit BOOLEAN DEFAULT TRUE, identifier OCTET STRING } A commit value of TRUE indicates a request to commit the transaction identified by the identifier. A commit value of FALSE indicates a request to abort the identified transaction. An End Transaction Response is an LDAPMessage sent in response to a End Transaction Request. Its response name is absent. The responseValue when present contains a BER-encoded MessageID. 2.5. Aborted Transaction Notice The Aborted Transaction Notice is an Unsolicited Notification message where the responseName is IANA-ASSIGNED-OID.4 and responseValue is present and contains a transaction identifier. 3. An LDAP Transaction 3.1. Extension Discovery Zeilenga LDAP Transactions [Page 3] INTERNET-DRAFT draft-zeilenga-ldap-txn-07 5 March 2006 To allow clients to discover support for this extension, servers implementing this specification SHOULD publish IANA-ASSIGNED-OID.1 and IANA-ASSIGNED-OID.3 as values of the 'supportedExtension' attribute [Models] within the Root DSE, and publish the IANA-ASSIGNED-OID.2 as a value of the 'supportedControl' attribute [Models] of the Root DSE. A server MAY choose to advertise this extension only when the client is authorized to use it. 3.2. Starting an Transactions A client wishing to preform a sequence of directory updates as an transaction issues a Start Transaction Request. A server which is willing and able to support transactions responds to this request with a Start Transaction Response providing a transaction identifier and with a resultCode of success. Otherwise, the server responds with a Start Transaction Response wth a result code other than success indicating the nature of the failure. The transaction identifier provided upon successful start of a transaction is used in subseqent protocol messages to identify this transaction. 3.3. Specification of a Transaction The client then may issue may issue one or more update (add, delete, modify, modifyDN) requests, each with a Transaction Specification control containing the transaction identifier indicating the updates are to processed as part of the transaction. Each of these update request MUST have a different MessageId value. If the server is unwilling or unable to attempt to process the requested update operation as part of the transaction, the server immediately returns the approrpiate response to the request with a resultCode indicating the nature of the failure. Otherwise, the server immediately returns success and the defers further processing of the operation is then deferred until settlement. If the server becomes unwilling or unable to continue the specification of a transaction, the server issues an Aborted Transaction Notice with a non-success resultCode indicating the nature of the failure. All operations that were to be processed as part of the transaction are implicitly abandoned. Upon receipt of an Aborted Transaction Notice, the client is to discontinue all use of the transaction identifier as the transaction is null and void. Any future use of identifier by the client will result in a response containing a non-success resultCode. Zeilenga LDAP Transactions [Page 4] INTERNET-DRAFT draft-zeilenga-ldap-txn-07 5 March 2006 3.4. Transaction Settlement A client requests settlement of transaction by issuing an End Transaction request for the transaction indicating whether it desires the transaction to be committed or aborted. Upon receipt of a request to abort the transaction, the server is to abort the identified transaction (abandoning all operations which are part of the transaction) and indicate that it has done so by returning an End Transaction response with a resultCode of success. Upon receipt of a request to commit the transaction, the server processes all update operations of the transaction as one atomic, isolated action with each requested update being processed in turn. Either all of the requested updates are to be successfully applied or none of the requested are to be applied. The server returns an End Transaction Response with a resultCode of success and no responseValue to indicate all the requested updates were applied. Otherwise, the server returns an End Transaction with an non-success resultCode indicating the nature of the failure. If the failure is associated with a particular update request, a responseValue containing its MessageID is returned. If the failure was not associated with any particular update request, no responseValue is returned. There is no requirement that a server serialize transactions, or updates requested outside of a transaction. That is, a server MAY process multiple commit requests (from one or more clients) acting upon different sets of entries concurrently. A server MUST avoid deadlock. 4. Distributed Directory Considerations The LDAP/X.500 models provide for distributed directory operations including server-side chaining and client-side chasing of operations. This document does not preclude servers from chaining operations which are part of a transaction. However, if a server does allow such chaining, it MUST ensure that transaction semantics are provided. This mechanism defined by this document does not support client-side chasing. Grouping cookies used to identify the transaction are specific to a particular client/server session. The LDAP/X.500 models provide for a single-master/multiple-shadow replication architecture. This document states no requirement that changes made to the directory based upon processing a transaction be replicated as one atomic action. That is, the client SHOULD NOT Zeilenga LDAP Transactions [Page 5] INTERNET-DRAFT draft-zeilenga-ldap-txn-07 5 March 2006 assume tight data consistency nor fast data convergence at shadow servers unless they have prior knowledge that such service is provided. Though this mechanism could be used to support replication, use in replication is not described in this document. The LDAP/X.500 models do not currently support a multi-master replication architecture and, hence, not considered by this specification. 5. Security Considerations Transactions mechanisms may be the target of denial of service attacks. Implementors should provide safeguards to ensure these mechanisms are not abused. General security considerations [Roadmap], especially associated with update operations [Protocol], apply to this extension. 6. IANA Considerations In accordance with [BCP64bis], it is requested that Internet Assigned Numbers Authority (IANA) make the following assignments. 6.1. Object Identifier Assignment of an LDAP Object Identifier to identify the protocol elements specified in this document this document is requested. Subject: Request for LDAP Object Identifier Registration Person & email address to contact for further information: Kurt Zeilenga Specification: RFC XXXX Author/Change Controller: IESG Comments: Identifies protocol elements for LDAP Transactions 6.2. LDAP Protocol Mechanism Registration of the protocol mechanisms specified in this document is requested. Subject: Request for LDAP Protocol Mechanism Registration Object Identifier: see table Description: see table Person & email address to contact for further information: Zeilenga LDAP Transactions [Page 6] INTERNET-DRAFT draft-zeilenga-ldap-txn-07 5 March 2006 Kurt Zeilenga Specification: RFC XXXX Author/Change Controller: IESG Comments: Object Identifier Type Description ------------------- ---- ----------------------------------------- IANA-ASSIGNED-OID.1 E Start Transaction Extended Request IANA-ASSIGNED-OID.2 C Transaction Specification Control IANA-ASSIGNED-OID.3 E End Transaction Extended Request 7. Acknowledgments The author gratefully acknowledges the contributions made by members of the Internet Engineering Task Force. 8. Author's Address Kurt D. Zeilenga OpenLDAP Foundation Email: Kurt@OpenLDAP.org 9. References [[Note to the RFC Editor: please replace the citation tags used in referencing Internet-Drafts with tags of the form RFCnnnn where possible.]] 9.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14 (also RFC 2119), March 1997. [Roadmap] Zeilenga, K. (editor), "LDAP: Technical Specification Road Map", draft-ietf-ldapbis-roadmap-xx.txt, a work in progress. [Protocol] Sermersheim, J. (editor), "LDAP: The Protocol", draft-ietf-ldapbis-protocol-xx.txt, a work in progress. [Models] Zeilenga, K. (editor), "LDAP: Directory Information Models", draft-ietf-ldapbis-models-xx.txt, a work in progress. Zeilenga LDAP Transactions [Page 7] INTERNET-DRAFT draft-zeilenga-ldap-txn-07 5 March 2006 [X.680] International Telecommunication Union - Telecommunication Standardization Sector, "Abstract Syntax Notation One (ASN.1) - Specification of Basic Notation", X.680(2002) (also ISO/IEC 8824-1:2002). [X.690] International Telecommunication Union - Telecommunication Standardization Sector, "Specification of ASN.1 encoding rules: Basic Encoding Rules (BER), Canonical Encoding Rules (CER), and Distinguished Encoding Rules (DER)", X.690(2002) (also ISO/IEC 8825-1:2002). 9.2. Informative References [ACID] Section 4 of ISO/IEC 10026-1:1992. [BCP64bis] Zeilenga, K., "IANA Considerations for LDAP", draft-ietf-ldapbis-bcp64-xx.txt, a work in progress. [X.500] International Telecommunication Union - Telecommunication Standardization Sector, "The Directory -- Overview of concepts, models and services," X.500(1993) (also ISO/IEC 9594-1:1994). [X.501] International Telecommunication Union - Telecommunication Standardization Sector, "The Directory -- Models," X.501(1993) (also ISO/IEC 9594-2:1994). 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