The information in this section applies to organizations that are designing, deploying, or operating an Active Directory infrastructure that satisfies the following requirements: Active Directory replication operates within the directory service component of the security subsystem.
The directory service component, Ntdsa.dll, is accessed through the Lightweight Directory Access Protocol (LDAP) network protocol and LDAP C application programming interface (API) for directory service updates, as implemented in Wldap32
The Directory Replication System (DRS) client and server components interact to transfer and apply Active Directory updates between domain controllers.When SMTP is used for the replication transport, on the source domain controller uses the Collaborative Data Object (CDO) library to build an SMTP file on disk with the replication data as the attached mail message. When the mail is scheduled for transfer by the mail server application, the SMTP service (Smtpsvc) delivers the mail message to the destination domain controller over TCP/IP and places the file in the drop directory on the destination domain controller. The following diagram shows the client-server architecture for replication clients and LDAP clients.Replication and LDAP Client-Server Architecture The following table describes the replication architecture components.Updated: November 19, 2014Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2, Windows Server 2008, Windows Server 2008 R2, Windows Server 2012, Windows Server 2012 R2 Active Directory data takes the form of objects that have properties, or attributes.Each object is an instance of an object class, and object classes and their respective attributes are defined in the Active Directory schema.
The values of the attributes define the object, and a change to a value of an attribute must be transferred from the domain controller on which it occurs to every other domain controller that stores a replica of that object.In Windows 2000 Server and Windows Server 2003, the directory service is named Active Directory.In Windows Server 2008 and Windows Server 2008 R2, the directory service is named Active Directory Domain Services (AD DS).The rest of this topic refers to Active Directory, but the information is also applicable to AD DS.Thus, Active Directory replicates directory data updates at the attribute level.In addition, updates from the same directory partition are replicated as a unit to the corresponding replica on the destination domain controller over the same connection to optimize network usage.