KCC: Within a Site, a Windows server 2003 service termed as KCC automatically produces a topology for replication among the domain controllers in the domain utilizing a ring structure. The KCC is a built in procedure that executes on all domain controllers.
The KCC examines the replication topology within a site of every 15 minute to make sure that it still works. When you add or eliminate a domain controller from the network or a site, the KCC re-configures the topology to relict the modification.