Network Working Group                                        R. Harrison
Request for Comments: 4373                                J. Sermersheim
Category: Informational                                     Novell, Inc.
                                                                 Y. Dong
                                                            January 2006


             Lightweight Directory Access Protocol (LDAP)
                Bulk Update/Replication Protocol (LBURP)

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   The Lightweight Directory Access Protocol (LDAP) Bulk
   Update/Replication Protocol (LBURP) allows an LDAP client to perform
   a bulk update to an LDAP server.  The protocol frames a sequenced set
   of update operations within a pair of LDAP extended operations to
   notify the server that the update operations in the framed set are
   related in such a way that the ordering of all operations can be
   preserved during processing even when they are sent asynchronously by
   the client.  Update operations can be grouped within a single
   protocol message to maximize the efficiency of client-server
   communication.

   The protocol is suitable for efficiently making a substantial set of
   updates to the entries in an LDAP server.

Table of Contents

   1. Introduction ....................................................3
   2. Conventions Used in This Document ...............................3
   3. Overview of Protocol ............................................3
      3.1. Update Initiation ..........................................4
      3.2. Update Stream ..............................................4
           3.2.1. LBURPUpdateRequest ..................................4
           3.2.2. LBURPUpdateResponse .................................4
      3.3. Update Termination .........................................4
      3.4. Applicability of Protocol ..................................5
   4. Description of Protocol Flow ....................................5
   5. Elements of Protocol ............................................6
      5.1. StartLBURPRequest ..........................................7
           5.1.1. updateStyleOID ......................................7
      5.2. StartLBURPResponse .........................................7
           5.2.1. maxOperations .......................................8
      5.3. LBURPUpdateRequest .........................................8
           5.3.1. sequenceNumber ......................................8
           5.3.2. UpdateOperationList .................................9
      5.4. LBURPUpdateResponse ........................................9
           5.4.1. OperationResults ...................................10
                  5.4.1.1. operationNumber ...........................10
                  5.4.1.2. ldapResult ................................10
      5.5. EndLBURPRequest ...........................................10
           5.5.1. sequenceNumber .....................................10
      5.6. EndLBURPResponse ..........................................11
   6. Semantics of the Incremental Update Style ......................11
   7. General LBURP Semantics ........................................11
   8. Security Considerations ........................................12
   9. IANA Considerations ............................................13
      9.1. LDAP Object Identifier Registrations ......................13
   10. Normative References ..........................................14
   11. Informative References ........................................14

1.  Introduction

   The Lightweight Directory Access Protocol (LDAP) Bulk
   Update/Replication Protocol (LBURP) arose from the need to allow an
   LDAP client to efficiently present large quantities of updates to an
   LDAP server and have the LDAP server efficiently process them.  LBURP
   introduces a minimum of new operational functionality to the LDAP
   protocol because the update requests sent by the client encapsulate
   standard LDAP [RFC2251] update operations.  However, this protocol
   greatly facilitates bulk updates by allowing the client to send the
   update operations asynchronously and still allow the server to
   maintain proper ordering of the operations.  It also allows the
   server to recognize the client's intent to perform a potentially
   large set of update operations and then to change its processing
   strategy to more efficiently process the operations.

2.  Conventions Used in This Document

   Imperative keywords defined in RFC 2119 [RFC2119] are used in this
   document, and carry the meanings described there.

   All Basic Encoding Rules (BER) [X.690] encodings follow the
   conventions found in section 5.1 of [RFC2251].

   The term "supplier" applies to an LDAP client or an LDAP server
   (acting as a client) that supplies a set of update operations to a
   consumer.

   The term "consumer" applies to an LDAP server that consumes (i.e.,
   processes) the sequenced set of update operations sent to it by a
   supplier.

3.  Overview of Protocol

   LBURP frames a set of update operations within a pair of LDAP
   extended operations that mark the beginning and end of the update
   set.  These updates are sent via LDAP extended operations, each
   containing a sequence number and a list of one or more update
   operations to be performed by the consumer.  Except for the fact that
   they are grouped together as part of a larger LDAP message, the
   update operations in each subset are encoded as LDAP update
   operations and use the LDAP Abstract Syntax Notation One (ASN.1)
   [X.680] message types specified in [RFC2251].

3.1.  Update Initiation

   The protocol is initiated when a supplier sends a StartLBURPRequest
   extended operation to a consumer as a notification that a stream of
   associated LBURPUpdateRequests will follow.  The supplier associates
   semantics with this stream of requests by including the Object
   Identifier (OID) of the bulk update/replication style in the
   StartLBURPRequest.  The consumer responds to the StartLBURPRequest
   with a StartLBURPResponse message.

3.2.  Update Stream

   After the consumer responds with a StartLBURPResponse, the supplier
   sends a stream of LBURPUpdateRequest messages to the consumer.
   Messages within this stream may be sent asynchronously to maximize
   the efficiency of the transfer.  The consumer responds to each
   LBURPUpdateRequest with an LBURPUpdateResponse message.

3.2.1.  LBURPUpdateRequest

   Each LBURPUpdateRequest contains a sequence number identifying its
   relative position within the update stream and an UpdateOperationList
   containing an ordered list of LDAP update operations to be applied to
   the Directory Information Tree (DIT).  The sequence number enables
   the consumer to process LBURPUpdateRequest messages in the order they
   were sent by the supplier even when they are sent asynchronously.
   The consumer processes each LBURPUpdateRequest according to the
   sequence number by applying the LDAP update operations in its
   UpdateOperationList to the DIT in the order they are listed.

3.2.2.  LBURPUpdateResponse

   When the consumer has processed the update operations from an
   UpdateOperationList, it sends an LBURPUpdateResponse to the supplier
   indicating the success or failure of the update operations contained
   within the corresponding LBURPUpdateRequest.

3.3.  Update Termination

   After the supplier has sent all of its LBURPUpdateRequest messages,
   it sends an EndLBURPRequest message to the consumer to terminate the
   update stream.  Upon servicing all LBURPOperation requests and
   receiving the EndLBURPRequest, the consumer responds with an
   EndLBURPResponse, and the update is complete.

3.4.  Applicability of Protocol

   LBURP is designed to facilitate the bulk update of LDAP servers.  It
   can also be used to synchronize directory information between a
   single master and multiple slaves.

   No attempt is made to deal with the issues associated with multiple-
   master replication environments (such as keeping modification times
   of attribute values) so that updates to the same entry on different
   replicas can be correctly ordered.  For this reason, when LBURP alone
   is used for replication, proper convergence of the data between all
   replicas can only be assured in a single-master replication
   environment.

4.  Description of Protocol Flow

   This section describes the LBURP protocol flow and the information
   contained in each protocol message.  Throughout this section, the
   client or server acting as a supplier is indicated by the letter "S",
   and the server acting as a consumer is indicated by the letter "C".
   The construct "S -> C" indicates that the supplier is sending an LDAP
   message to the consumer, and "C -> S" indicates that the consumer is
   sending an LDAP message to the supplier.  Note that the protocol flow
   below assumes that a properly authenticated LDAP session has already
   been established between the supplier and consumer.

       S -> C: StartLBURPRequest message.  The parameter is:

                  1) OID for the LBURP update style (see section 5.1.1).

       C -> S: StartLBURPResponse message.  The parameter is:

                  1) An optional maxOperations instruction
                     (see section 5.2.1).

       S -> C: An update stream consisting of zero or more
               LBURPUpdateRequest messages.  The requests MAY be sent
               asynchronously.  The parameters are:

                  1) A sequence number specifying the order of
                     this LBURPUpdateRequest with respect to the
                     other LBURPUpdateRequest messages in the update
                     stream (see section 5.3.1).

                  2) LBURPUpdateRequest.updateOperationList, a list
                     of one or more LDAP update operations (see section
                     5.3.2).

               The consumer processes the LBURPUpdateRequest messages
               in the order of their sequence numbers and applies the
               LDAP update operations contained within each
               LBURPUpdateRequest to the DIT in the order they are
               listed.

       C -> S: LBURPUpdateResponse message.  This is sent when the
               consumer completes processing the update operations
               from each LBURPUpdateRequest.updateOperationList.

       S -> C: EndLBURPRequest message.  This is sent after the
               supplier sends all of its LBURPUpdateRequest messages
               to the consumer.  The parameter is:

                  1) A sequence number that is one greater than the
                     sequence number of the last LBURPUpdateRequest
                     message in the update stream.  This allows the
                     EndLBURPRequest to also be sent asynchronously.

       C -> S: EndLBURPResponse message.  This is sent in response to
               the EndLBURPRequest after the consumer has serviced
               all LBURPOperation requests.

5.  Elements of Protocol

   LBURP uses two LDAP ExtendedRequest messages--StartLBURPRequest and
   EndLBURPRequest--to initiate and terminate the protocol.  A third
   LDAP ExtendedRequest message--LBURPUpdateRequest--is used to send
   update operations from the supplier to the consumer.  These three
   requests along with their corresponding responses comprise the entire
   protocol.

   LBURP request messages are defined in terms of the LDAP
   ExtendedRequest [RFC2251] as follows:

        ExtendedRequest ::= [APPLICATION 23] SEQUENCE {
            requestName    [0] LDAPOID,
            requestValue   [1] OCTET STRING OPTIONAL
        }

   LBURP response messages are defined in terms of the LDAP
   ExtendedResponse [RFC2251] as follows:

       ExtendedResponse ::= [APPLICATION 24] SEQUENCE {
           COMPONENTS of LDAPResult,
           responseName  [10] LDAPOID OPTIONAL,
           response      [11] OCTET STRING OPTIONAL
        }

5.1.  StartLBURPRequest

   The requestName value of the StartLBURPRequest is OID 1.3.6.1.1.17.1.

   The requestValue of the StartLBURPRequest contains the BER-encoding
   of the following ASN.1:

       StartLBURPRequestValue ::= SEQUENCE {
           updateStyleOID LDAPOID
       }

   LDAPOID is defined in [RFC2251], section 4.1.2.

5.1.1.  updateStyleOID

   The updateStyleOID is an OID that uniquely identifies the LBURP
   update style being used.  This document defines one LBURP update
   semantic style that can be transmitted between the StartLBURPRequest
   and EndLBURPRequest.  The updateStyleOID is included in the protocol
   for future expansion of additional update styles.  For example, a
   future specification might define an update style with semantics to
   replace all existing entries with a new set of entries and thus only
   allows the Add operation.

   The updateStyleOID for the LBURP Incremental Update style is
   1.3.6.1.1.17.7.  The semantics of this update style are described in
   section 6.

5.2.  StartLBURPResponse

   The responseName of the StartLBURPResponse is the OID 1.3.6.1.1.17.2.

   The optional response element contains the BER-encoding of the
   following ASN.1:

       StartLBURPResponseValue ::= maxOperations

       maxOperations ::= INTEGER (0 .. maxInt)

       maxInt INTEGER ::= 2147483647 -- (2^^31 - 1) --

5.2.1.  maxOperations

   When present, the value of maxOperations instructs the supplier to
   send no more than that number of update operations per
   LBURPUpdateRequest.updateOperationList (see section 5.3.2).  If the
   consumer does not send a maxOperations value, it MUST be prepared to
   accept any number of update operations per
   LBURPUpdateRequest.updateOperationList.  The supplier MAY send fewer
   but MUST NOT send more than maxOperations update operations in a
   single LBURPUpdateRequest.updateOperationList.

5.3.  LBURPUpdateRequest

   The LBURPUpdateRequest message is used to send a set of zero or more
   LDAP update operations from the supplier to the consumer along with
   sequencing information that enables the consumer to maintain the
   proper sequencing of multiple asynchronous LBURPUpdateRequest
   messages.

   The requestName of the LBURPUpdateRequest is the OID 1.3.6.1.1.17.5.

   The requestValue of an LBURPOperation contains the BER-encoding of
   the following ASN.1:

       LBURPUpdateRequestValue ::= SEQUENCE {
           sequenceNumber INTEGER (1 .. maxInt),
           updateOperationList UpdateOperationList
       }

5.3.1.  sequenceNumber

   The sequenceNumber orders associated LBURPOperation requests.  This
   enables the consumer to process LBURPOperation requests in the order
   specified by the supplier.  The supplier MUST set the value of
   sequenceNumber of the first LBURPUpdateRequest to 1, and MUST
   increment the value of sequenceNumber by 1 for each succeeding
   LBURPUpdateRequest.  In the unlikely event that the number of
   LBURPUpdateRequest messages exceeds maxInt, a sequenceNumber value of
   1 is deemed to be the succeeding sequence number following a sequence
   number of maxInt.

5.3.2.  UpdateOperationList

   The UpdateOperationList is a list of one or more standard LDAP update
   requests and is defined as follows:

       UpdateOperationList ::= SEQUENCE OF SEQUENCE{
           updateOperation CHOICE {
              addRequest       AddRequest,
              modifyRequest    ModifyRequest,
              delRequest       DelRequest,
              modDNRequest     ModifyDNRequest
           },
           controls       [0] Controls OPTIONAL
       }

   AddRequest, ModifyRequest, DelRequest, and ModifyDNRequest are
   defined in [RFC2251], sections 4.6, 4.7, 4.8, and 4.9.

   The LDAP update requests in the UpdateOperationList MUST be applied
   to the DIT in the order in which they are listed.

5.4.  LBURPUpdateResponse

   An LBURPUpdateResponse message is sent from the consumer to the
   supplier to signal that all of the update operations from the
   UpdateOperationList of an LBURPUpdateRequest have been completed and
   to give the results for the update operations from that list.

   The responseName of the LBURPUpdateResponse is the OID
   1.3.6.1.1.17.6.

   If the consumer server cannot successfully decode an
   LBURPUpdateRequest in its entirety, the resultCode for the
   corresponding LBURPUpdateResponse is set to protocolError and the
   response element is omitted.  Updates from the LBURPUpdateRequest
   SHALL NOT be committed to the DIT in this circumstance.

   If the status of all of the update operations being reported by an
   LBURPUpdateResponse message is success, the resultCode of the
   LBURPUpdateResponse message is set to success and the response
   element is omitted.

   If the status of any of the update operations being reported by an
   LBURPUpdateResponse message is something other than success, the
   resultCode for the entire LBURPUpdateResponse is set to other to
   signal that the response element is present.

5.4.1.  OperationResults

   When a response element is included in an LBURPUpdateResponse
   message, it contains the BER-encoding of the following ASN.1:

       OperationResults ::= SEQUENCE OF OperationResult

       OperationResult ::= SEQUENCE {
          operationNumber    INTEGER,
          ldapResult         LDAPResult
       }

   An OperationResult is included for each operation from the
   UpdateOperationList that failed during processing.

5.4.1.1.  operationNumber

   The operationNumber identifies the LDAP update operation from the
   UpdateOperationList of the LBURPUpdateRequest that failed.
   Operations are numbered beginning at 1.

5.4.1.2.  ldapResult

   The ldapResult included in the OperationResult is the same ldapResult
   that would be sent for the update operation that failed if it had
   failed while being processed as a normal LDAP update operation.
   LDAPResult is defined in [RFC2251], section 4.1.10.

5.5.  EndLBURPRequest

   The requestName of the EndLBURPRequest is the OID 1.3.6.1.1.17.3.

   The requestValue contains the BER-encoding of the following ASN.1:

        EndLBURPRequestValue::= SEQUENCE {
            sequenceNumber INTEGER (1 .. maxInt)
        }

5.5.1.  sequenceNumber

   The value in sequenceNumber is one greater than the last
   LBURPUpdateRequest.sequenceNumber in the update stream.  It allows
   the server to know when it has received all outstanding asynchronous
   LBURPUpdateRequests.

5.6.  EndLBURPResponse

   The responseName of the EndLBURPResponse is the OID 1.3.6.1.1.17.4.

   There is no response element in the EndLBURPResponse message.

6.  Semantics of the Incremental Update Style

   The initial state of entries in the consumer's DIT plus the
   LBURPUpdateRequest messages in the update stream collectively
   represent the desired final state of the consumer's DIT.  All LDAP
   update operations defined in [RFC2251]--Add, Modify, Delete, and
   Modify DN--are allowed in the incremental update stream.  All of the
   semantics of those operations are in effect, so for instance, an
   attempt to add an entry that already exists will fail just as it
   would during a normal LDAP Add operation.

7.  General LBURP Semantics

   The consumer server may take any action required to efficiently
   process the updates sent via LBURP, as long as the final state is
   equivalent to that which would have been achieved if the updates in
   the update stream had been applied to the DIT using normal LDAP
   update operations.

   The LBURPUpdateRequest messages that form the update stream MAY be
   sent asynchronously by the supplier to the consumer.  This means that
   the supplier need not wait for an LBURPUpdateResponse message for one
   LBURPUpdateRequest message before sending the next LBURPUpdateRequest
   message.

   When the LBURP update stream contains a request that affects multiple
   Directory System Agents (DSAs), the consumer MAY choose to perform
   the request or return a resultCode value of affectsMultipleDSAs.  As
   with any LDAP operation, a consumer MAY send a resultCode value of
   referral as part of the OperationResult element for any operation on
   an entry that it does not contain.  If the consumer is configured to
   do so, it MAY chain on behalf of the supplier to complete the update
   operation instead.

   While a consumer server is processing an LBURP update stream, it may
   choose not to service LDAP requests on other connections.  This
   provision is designed to allow implementers the freedom to implement
   highly-efficient methods of handling the update stream without being
   constrained by the need to maintain a live, working DIT database
   while doing so.

   If a consumer chooses to refuse LDAP operation requests from other
   suppliers during LBURP update, it is RECOMMENDED that the consumer
   refer those requests to another server that has the appropriate data
   to complete the operation.

   Unless attribute values specifying timestamps are included as part of
   the update stream, updates made using LBURP are treated the same as
   other LDAP operations wherein they are deemed to occur at the
   present.  Consumers MAY store timestamp values sent by suppliers but
   are not required to do so.

   Implementations may choose to perform the operations in the update
   stream with special permissions to improve performance.

   Consumer implementations should include functionality to detect and
   terminate connections on which an LBURP session has been initiated
   but information (such as the EndLBURPRequest) needed to complete the
   LBURP session is never received.  A timeout is one mechanism that can
   be used to accomplish this.

8.  Security Considerations

   Implementations should ensure that a supplier making an LBURP request
   is properly authenticated and authorized to make the updates
   requested.  There is a potential for loss of data if updates are made
   to the DIT without proper authorization.  If LBURP is used for
   replication, implementers should note that unlike other replication
   protocols, no existing replication agreement between supplier and
   consumer is required.  These risks increase if the consumer server
   also processes the update stream with special permissions to improve
   performance.  For these reasons, implementers should carefully
   consider which permissions should be required to perform LBURP
   operations and take steps to ensure that only connections with
   appropriate authorization are allowed to perform them.

   The data contained in the update stream may contain passwords and
   other sensitive data.  Care should be taken to properly safeguard
   this information while in transit between supplier and consumer.  The
   StartTLS [RFC2830] operation is one mechanism that can be used to
   provide data confidentiality and integrity services for this purpose.

   As with any asynchronous LDAP operation, it may be possible for an
   LBURP supplier to send asynchronous LBURPUpdateRequest messages to
   the consumer faster than the consumer can process them.  Consumer
   implementers should take steps to prevent LBURP suppliers from
   interfering with the normal operation of a consumer server by issuing
   a rapid stream of asynchronous LBURPUpdateRequest messages.

9.  IANA Considerations

   Registration of the following values has been made by the IANA
   [RFC3383].

9.1.  LDAP Object Identifier Registrations

   The IANA has registered LDAP Object Identifiers identifying the
   protocol elements defined in this technical specification.  The
   following registration template was provided:

   Subject: Request for LDAP OID Registration
   Person & email address to contact for further information:
       Roger Harrison
       rharrison@novell.com
   Specification: RFC 4373
   Author/Change Controller: IESG
   Comments:
   Seven delegations will be made under the assigned OID.  The
   following 6 OIDs are Protocol Mechanism OIDs of type "E"
   (supportedExtension):

   1.3.6.1.1.17.1 StartLBURPRequest LDAP ExtendedRequest message
   1.3.6.1.1.17.2 StartLBURPResponse LDAP ExtendedResponse message
   1.3.6.1.1.17.3 EndLBURPRequest LDAP ExtendedRequest message
   1.3.6.1.1.17.4 EndLBURPResponse LDAP ExtendedResponse message
   1.3.6.1.1.17.5 LBURPUpdateRequest LDAP ExtendedRequest message
   1.3.6.1.1.17.6 LBURPUpdateResponse LDAP ExtendedResponse message

   The following 1 OID is a Protocol Mechanism OID of type "F"
   (supportedFeature):

   1.3.6.1.1.17.7 LBURP Incremental Update style OID

10.  Normative References

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

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

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

   [X.680]    ITU-T Recommendation X.680 (07/2002) | ISO/IEC 8824-1:2002
              "Information Technology - Abstract Syntax Notation One
              (ASN.1): Specification of basic notation"

   [X.690]    ITU-T Rec. X.690 (07/2002) | ISO/IEC 8825-1:2002,
              "Information technology - ASN.1 encoding rules:
              Specification of Basic Encoding Rules (BER), Canonical
              Encoding Rules (CER) and Distinguished Encoding Rules
              (DER)", 2002.

11.  Informative References

   [RFC2830]  Hodges, J., Morgan, R., and M. Wahl, "Lightweight
              Directory Access Protocol (v3): Extension for Transport
              Layer Security", RFC 2830, May 2000.

Authors' Addresses

   Roger Harrison
   Novell, Inc.
   1800 S. Novell Place
   Provo, UT 84606

   Phone: +1 801 861 2642
   EMail: rharrison@novell.com


   Jim Sermersheim
   Novell, Inc.
   1800 S. Novell Place
   Provo, UT 84606

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


   Yulin Dong

   EMail: yulindong@gmail.com

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