http://technet.microsoft.com/en-us/windowsserver/bb530956
http://technet.microsoft.com/en-us/library/cc754697.aspx
Use Active Directory Sites and Services to manage sites in an Active Directory.
http://technet.microsoft.com/en-us/library/cc794776%28WS.10%29.aspx
The Intersite Topology Generator (ISTG) is the domain controller in each site that is responsible for generating the intersite topology.
To determine the ISTG role owner for a site: