With in a Site, a Windows server 2003 service known as the KCC automatically generates a topology for replication among the domain controllers in the domain using a ring structure.Th Kcc is a built in process that runs on all domain controllers.

The KCC analyzes the replication topology within a site every 15 minute to ensure that it still works. If you add or remove a domain controller from the network or a site, the KCC reconfigures the topology to relect the change.