To view the Replication Within Sites presentation, open the Web page on the Student Materials compact disc, click Multimedia, and then click the title of the presentation. Do not open this presentation unless the instructor tells you to.
At the end of this presentation, you will be able to:
■ Define replication and predict when it will occur.
■ Describe how replication occurs.
■ Describe replication conflicts and how to resolve them.
The key points of Active Directory replication within a site are:
■ When does replication occur? When there is:
• An addition of an object to Active Directory.
• A modification of an object's attribute values.
• A name change of an object's container.
• A deletion of an object from the directory.
■ Change notification. When a change occurs on a domain controller, the domain controller notifies its replication partners within the same site. This process is called change notification.
■ Replication latency. The delay between the time that a change occurs and the time that the update reaches all of the domain controllers in a site. The default replication latency is 15 seconds.
■ Urgent replication. Rather than wait the default 15 seconds, security-sensitive attribute updates trigger an immediate change notification.
■ Convergence. Each update in Active Directory eventually propagates to every domain controller in the site that hosts the partition on which the update was made. This complete propagation is called convergence.
■ Propagation dampening. The process of preventing unnecessary replication. Each domain controller assigns every changed attribute and object an Update Sequence Number (USN) to prevent unnecessary replication.
■ Conflicts. When concurrent updates that originate on two separate master replicas are inconsistent, conflicts may arise. Active Directory resolves three types of conflicts: attribute, deleted container, and Relative Distinguished Name (RDN) conflicts.
■ Globally unique stamp. Active Directory maintains a stamp that contains the version number, timestamp, and server globally unique identifier (GUID) that Active Directory created during the originating update.
Note For more information about USNs, see "Replication Within Sites" in Module 7 on the Appendices page on the Student Materials compact disc.
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