Mitosis has been edited by Emmanuel Lécharny (Feb 08, 2009).

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This site is in the process of being reviewed and updated.


Mitosis is the replication system built inside Apache Directory Server. It's a Multi-Master replication system.

Replication Requirements

Sources of Information

There are multiple sources of information that should be considered when researching MMR for LDAP:

  • ACM & IEEE papers on MMR in general
  • How other existing MMR implementations work (LDAP and non-LDAP)
  • X.500, RFCs and IETF Drafts
  • Analysis of conflict scenarios
  • User feedback on existing Mitosis implementation

RFC Related to Replication

LDAP RFCs Can Be Trusted

IETF RFC are definitive sources of information unlike drafts which have errors and gross conflicts/misunderstandings WRT LDAP and X.500.

LDAPv3 Content Synchronization Operation (RFC 4533)

This specification describes the Lightweight Directory Access
   Protocol (LDAP) Content Synchronization Operation.  The operation
   allows a client to maintain a copy of a fragment of the Directory
   Information Tree (DIT).  It supports both polling for changes and
   listening for changes.  The operation is defined as an extension of
   the LDAP Search Operation.

LDAPv3 Replication Requirements (RFC 3384)

This document discusses the fundamental requirements for replication
   of data accessible via the Lightweight Directory Access Protocol
   (version 3) (LDAPv3).  It is intended to be a gathering place for
   general replication requirements needed to provide interoperability
   between informational directories.


LDAP entryUUID Operational Attribute (RFC 4530)

This document describes the LDAP/X.500 'entryUUID' operational
   attribute and associated matching rules and syntax.  The attribute
   holds a server-assigned Universally Unique Identifier (UUID) for the
   object.  Directory clients may use this attribute to distinguish
   objects identified by a distinguished name or to locate an object
   after renaming.


IETF Drafts Related to Replication

Drafts Are Not To Be Trusted

Most draft specifications contain serious conflicts with LDAP and X.500 concepts. Several gross misunderstandings of the protocol are evident. While reading drafts to consider some potential ideas on replication please keep this in mind and validate the concepts found in them against LDAP RFC and X.500 specifications.

LDAP Multi-Master Replication Protocol

This paper defines a multi-master, incremental replication protocol
   using the LDAP protocol [LDAPv3]. This protocol uses and builds upon
   previous LDAP support protocols, namely the changelog [change] and LDIF
   [LDIF] protocols. It defines the use of two types of transport protocols
   for replication data, and specifies the schema that must be supported by
   a server that wishes to participate in replication activities using this
   protocol. In addition, it specifies a conflict resolution mechanism for
   integrating updates from multiple servers.


Mandatory LDAP Replica Management

The goal of standards for LDAP replication is to allow interoperable
   replication among products from many different vendors.  Defining the
   mechanism to move data among replicas is a necessary part of this work,
   but management of the replicated environment must also be standardized
   for replication to be truly interoperable.

   This document presents the replication management functions that must
   be performed.  Whenever possible, these functions are defined in terms
   of existing LDAP functionality using existing LDAP operations and
   existing data definitions.  In some cases, changes or additions to the
   existing model are required, and specifications for these changes are
   included in this document.


General Usage Profile for LDAPv3 Replication

Support for replication in LDAP directory systems is often one of the
   key factors in the decision to deploy them.  But replication brings
   design constraints along with its benefits.

   We discuss some of the factors that should be taken into consideration
   when designing a replicated directory system.  Both programming and
   architectural/operational concerns are addressed and both single- and
   multi-master directories are considered.


The LDUP Replication Update Protocol

The protocol described in this document is designed to allow one
   LDAP server to replicate its directory content to another LDAP
   server. The protocol is designed to be used in a replication
   configuration where multiple updateable servers are present.
   Provisions are made in the protocol to carry information that allows
   the server receiving updates to apply a total ordering to all
   updates in the replicated system. This total ordering allows all
   replicas to correctly resolve conflicts that arise when LDAP clients
   submit changes to different servers that later replicate to one

   All protocol elements described here are LDAPv3 extended operations
   and controls. LDAPv3 is described in RFC 2251 [LDAPv3]. Some LDAPv3
   extended operations and controls described here are LDAPv3 extended
   operations used to group related operations. The protocol elements
   used for grouping are described in LDAPv3: Grouping of Related
   Operations [GROUPING|].

   Certain terms used in this document are defined in the document
   "LDAP Replication Architecture" [ARCHITECTURE|].


LDAP Subentry Schema

This document describes an administrative model for LDAP,
   and an object class called ldapSubEntry and a control
   ldapSubentriesControl (to control the visibility of entries
   of type ldapSubEntry) that are to be used by directory
   servers claiming support for the administrative model
   defined here.


  • Alex Karasulu This draft grossly violates X.500 rules regarding subentries by suggesting they can contain subordinate entries (for replication agreements)

LDUP Replication Information Model

[LDUP Model] describes the architectural approach to replication of
   LDAP directory contents.  This document describes the information
   model and schema elements which support LDAP Replication Services
   which conform to [LDUP Model].

   Directory schema is extended to provide object classes, subentries,
   and attributes to describe areas of the namespace which are under
   common administrative authority, units of replication (i.e.,
   subtrees, or partitions of the namespace, which are replicated),
   servers which hold replicas of various types for the various
   partitions of the namespace, which namespaces are held on given
   servers, and the progress of various namespace management and
   replication operations.  Among other things, this knowledge of where
   directory content is located will provide the basis for dynamic
   generation of LDAP referrals for clients who can follow them.

   The controlling framework by which the relationships, types, and
   health of replicas of the directory content will be defined so that,
   as much as possible, directory content is itself used to monitor and
   control the environment.

   Security information, including access control policy identifiers
   and information will be treated as directory content by the
   replication protocols when specified by the LDAPEXT group.

   The information model will describe required and optional house-
   keeping duties for compliant systems to implement, such as garbage
   collection of deleted objects, reconciliation of moved and renamed
   objects, update sequencing and transaction bracketing of changes,


  • Alex Karasulu Again all these LDUP drafts if I recall correctly make some presumptions about subentries that violate X.500 standards. I will confirm for sure as I make another pass through these drafts and update my comments.

LDUP Update Reconciliation Procedures

This document describes the procedures used by Lightweight Directory
   Access Protocol (LDAP) directory servers or X.500 directory servers
   to reconcile updates performed by autonomously operating directory
   servers in a distributed, replicated directory service, using the
   LDAP Duplication/Replication/Update protocols.








Lightweight Directory Access Protocol (LDAP) Client Update Protocol (LCUP)
Lightweight Directory Access Protocol (LDAP) Bulk Update/Replication Protocol (LBURP)
I-Ds List Working Group, LDAP Duplication/Replication/Update Protocols (ldup)

Other documents are articles about replication :
LDAP Duplication/Replication/Update Protocols (ldup)
LDAP Replication Draft Analysis and Design Document
Designating and Implementing Asynchronous Collaborative Applications with Bayou

General doctuments and specification about MMR :
Wikipedia link on Multi-master replication
Challenges Involved in Multimaster Replication
Active Directory infos about MMR
Oracle document about MMR
Active Directory replication model
eDirectory Synchronization and Background Processes

Paper by Kurt Zeilenga, and refutations:
MMR considered harmful
Read Only replicas considered harmful
Serial numbers and MMR
Is MMR really harmful?

There are some drafts called Mitosis Functionnal Abstract where some thoughts have been collected.

Configuration guide


Developper guide

Every information about developpement can be found here : Mitosis Development Guide..

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