Active Directory Replication

Replication Model Benefits

The key benefits of the Active Directory replication model are the following:

Active Directory always replicates changes to the correct object and is able to differentiate between a deleted object and a new object that has the same distinguished name (also known as "DN"). This is possible because the process of replication is based on the globally unique identifiers (GUIDs) of directory objects, not on their distinguished names.
This replication model minimizes update conflicts and supports attribute-level conflict detection and resolution. Only those attribute values that have changed, not the entire object, are transmitted as updates.
Wide area network (WAN) communication is minimized through support for store-and-forward replication and the compression of replication data between sites. Servers contain only a subset of the objects in the entire directory — those that are required for the forest and those that are specific to the server domain. Even though all Global Catalog servers contain all objects in the forest, they contain only a subset of the attributes for these objects.
Replication topology (including choice of transports) is flexible to make the best use of different network topologies. Sites provide an intelligent basis for automatically generating replication topology and helping clients perform intelligent domain controller selection.
System configuration remains flexible because the sites are not tied to the partition structure of the directory.
Speed over high-latency communication links is enhanced because the number of network round-trips by replication protocols is minimized.
Dependencies on other services, such as time synchronization (W32Time), are minimized.