What is the Active Directory Replication Model?

The replication model used in Microsoft® Active Directory™ is called multi-master loose consistency with convergence. In this model, the directory can have many replicas; a replication system propagates changes made at any given replica to all other replicas. The replicas are not guaranteed to be consistent with each other at any particular point in time ("loose consistency"), since changes can be applied to any replica at any time ("multi-master"). If the system is allowed to reach a steady state, in which no new updates are occurring and all previous updates have been completely replicated, all replicas are guaranteed to converge on the same set of values ("convergence").