Active Directory, 4th Edition

Chapter 5. Site Topology and Replication

This chapter introduces a major feature of Active Directory: multimaster replication. Active Directory was one of the first LDAP-based directories to offer multimaster replication. Most directories replicate data from a single master server to subordinate servers. This is how replication worked in Windows NT 4.0 for example. Obviously, there are several potential problems with a single-master replication scheme, including single point of failure for updates, geographic distance from master to clients performing the updates, and less efficient replication due to single originating location of updates. Active Directory replication addresses these issues, but with a price. To get the benefit of a multimaster replication, you must first create a site topology that describes the network and helps define how domain controllers should replicate with each other. In large environments, building and maintaining a site topology can be a significant amount of work.

This chapter looks at the basics of how sites and replication work in Active Directory. In Chapter 11, we’ll describe the physical infrastructure of a network layout using sites. We’ll also discuss in that chapter how the Knowledge Consistency Checker (KCC) sets up and manages the replication connections and details on how to effectively design and tailor sites, site links, and replication in Active Directory.

Site Topology

The Active Directory site topology is the map that describes the network ...