Replication can balance the load on Directory Server in the following ways:
By spreading search activities across several servers
By dedicating specific servers to specific tasks or applications
Generally, if the Number of hosts calculated in Assessing Initial Replication Requirements is about 16, or not significantly larger, your topology should include only master servers in a fully connected topology. Fully connected means that every master replicates to every other master in the topology.
The Number of hosts is approximate and depends on the hardware and other details of the deployment.
The following figure assumes that the Number of hosts is two. LDAP operations are divided between two master servers, based on the type of client application. This strategy reduces the load that is placed on each server and increases the total number of operations that can be served by the deployment.
For a similar scenario in a global deployment, see Multi-Master Replication Over WAN.