Sites

A site is a location in a network holding Active Directory servers. A site is defined as one or more well-connected TCP/IP subnets. "Well-connected" means that network connectivity is highly reliable and fast. Defining a site as a set of subnets allows administrators to quickly and easily configure Active Directory access and replication topology to take advantage of the physical network. When users log in, Active Directory clients find Active Directory servers in the same site as the user. Since machines in the same site are close to each other in network terms, communication among machines in the site is reliable, fast, and efficient. Determining the local site at login time is easy because the user's workstation already knows what TCP/IP subnet it is on, and subnets translate directly to Active Directory sites.