Updated: August 22, 2005
Applies To: Windows Server 2003 R2
You can optimize the replication efficiency and reduce the administrative overhead of your network by establishing sites appropriately. The most effective number of sites depends on the physical design of your network. When you first create a new configuration set for Active Directory Application Mode (ADAM), a single, default site (called Default-First-Site-Name) is created that represents your entire network. A single site can be very efficient for a single location network that is completely connected by high-speed bandwidth. If your network contains multiple geographic locations that communicate over low-speed, wide area network (WAN) connections, establishing multiple sites gives you more detailed control of replication behavior, and it reduces network traffic on the WAN that connects the sites. You can administer site objects and site link objects through ADAM ADSI Edit.
Bandwidth as an important consideration
Within a site, bandwidth affects how efficiently replication can work. The frequency with which intrasite replication occurs requires high-speed bandwidth to function most effectively. Before you create a new site, make sure that high-speed bandwidth connects all computers in the site candidate. Any area where domain controllers are connected by 10 megabits per second (Mbps) or more of bandwidth is a good site candidate.
When to establish a single site
If you have a single local area network (LAN) consisting of a single location, or if your network consists of a series of closely located locations (as in a campus), in which all locations are connected by a high-speed backbone, using the default site as the single site in replication topology can simplify replication management. In a single-site topology, all replication on your network occurs as intrasite replication, which requires no manual replication configuration. In a single-site design, all ADAM instances also remain very current with respect to directory changes, because directory updates are replicated almost immediately.
When to establish multiple sites
When your network consists of multiple geographic locations connected by a WAN, establishing separate sites for each location provides the following benefits:
Efficient use of WAN bandwidth for replication
Detailed control of replication behavior
Physically separate network locations typically communicate over WAN connections, which are most often characterized by low-speed bandwidth. By creating a separate site for each physical location on your network, you ensure that ADAM instances communicating over WAN connections use intersite replication, which is specifically designed for efficiency over low-bandwidth connections. When you create a site object, you also need to create a servers container within the site object. To move an ADAM instance to a new site object, you move the ADAM instance into the servers container of the site. For more information, see Add a site object and servers container and Move an ADAM instance to a site object.
Site link objects represent the network links between the sites on your network. When you create a new site object in ADAM, add the site object to a site link object. Until you add the new site to a site link object, any ADAM instances in the site will not be able to replicate to ADAM instances outside the site. You can add a new site object to the default site link object. Or, you can create additional site link objects, giving you more detailed control over the relative cost of replication over different WAN connections on your network.
With multiple sites, you have more detailed control of replication behavior through configurable intersite replication settings. These settings include the relative cost of different replication paths and the availability of connections for use by replication. For more information, see Configure replication availability on a site link and Set the cost on a site link object.