This chapter explored two Active Directory communication technologies: replication and trusts. The Active Directory uses multi-master replication, in which all domain controllers are responsible for sending and receiving Active Directory updates. Replication occurs through the use of USNs, as well as timestamps for tie-breaking purposes. The Active Directory configures its own intrasite replication topology, and contains automatic methods to solve collisions and provide propagation dampening. Trust relationships allow domain users to access resources in different domains. In the past, trust relationships could be rather tricky, but Windows 2000 uses transitive trust relationships that are automatically configured for domains in the tree or forest. You can adjust the trust settings and configure trust cross-links by using the Active Directory Domains and Trusts tool.