Store-and-Forward Replication

Store-and-forward replication is designed to reduce communication over slow WAN links. An update replicates first to nearby replicas and from there to replicas that are farther away.

Store-and-forward replication eliminates the need to send every change directly from the server that is accepting the change to all other servers that hold replicas of the affected directory partition. A server that is accepting a change can send the change to nearby servers. One of these servers can then send the change to a distant server, which in turn forwards the change to nearby servers. Store-and-forward greatly reduces the WAN traffic that is produced by replication.

To alleviate the administrative complexity of managing connections between all domain controllers, the system can create the topology automatically. You administer replication indirectly by defining a simplified network model within your directory. This model is based on concepts of sites, site links, and site link bridges. Based on this model, Active Directory creates replication connections that allow Active Directory to perform replication. When failures occur, Active Directory modifies replication connections to keep replication going. You also have the option of manually creating replication connections to exert finer control. Manually created connections coexist with automatically generated ones, so if you want to fine-tune one connection, you need not sacrifice the benefits of automatic management for other connections.