An Active Directory object that represents a set of sites that can communicate at uniform cost through some intersite transport. For Internet Protocol (IP) transport, a typical site link connects just two sites and corresponds to an actual wide area network (WAN) link. An IP site link connecting more than two sites might correspond to an asynchronous transfer mode (ATM) backbone connecting more than two clusters of buildings on a large campus or several offices in a large metropolitan area connected via leased lines and IP routers.