How Information Is Replicated
Active Directory replicates information in two ways: intrasite (within a site) and . The need for up-to-date directory information is balanced with the limitations imposed by available network bandwidth.
Intrasite Replication Within a site, a Windows Server 2003 service known as the knowledge consistency checker (KCC) automatically generates a topology for replication among domain controllers in the same domain using a ring structure. The KCC is a built-in process that ains on all domain controllers. The topology defines the path for directory updates to flow from one domain controller to another until all domain controllers in the site receive the directory updates. The KCC determines which servers are best suited to replicate with each other, and designates certain domain controllers as replication partners on the basis of connectivity, history of successful replication, and the matching of full and partial replicas. Domain controllers can have more than one replication partner. The KCC then builds connection objects that represent replication connections between the replication partners.
The ring structure ensures that there are at least two replication paths from one domain controller to another; if one domain controller is down temporarily, replication still continues to all other domain controllers, as shown in Figure 1-10.
The KCC analyzes the replication topology within a site every 15 minutes 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 reflect the change.
When more than seven domain controllers are added to a site, the KCC creates additional connection objects across the ring structure so that if a change occurs at any one domain controller, replication partners are available to ensure that no domain controller is more than three replication hops from another domain controller, as shown in Figure 1-11. These optimizing connections are created at random and are not necessarily created on every domain controller.
Extensions to schema in a global catalog should be approached carefully. Schema extensions can have disastrous effects on large networks because the extensions cannot be deleted (only disabled) and because of the large amount of network traffic generated as the extensions are synchronized throughout the forest.
