In this illustration a load balancer sits above two single sign-on middle tier computers. Arrows running from the load balancer to these computers indicate that it serves both middle tiers. Atop the load balancer sits the browser. Beneath the middle tiers is a load balancer. Beneath the load balancer are two dotted line boxes, each containing an Oracle Internet Directory server and identity management infrastructure database. The dotted line boxes indicate that the directory server and infrastructure database reside on the same computer. Arrows running from the single sign-on middle tiers to the load balancer and from the load balancer to the directory servers indicate that the directory load balancer balances connection requests between two directories. The two dotted line boxes are joined by an arrow labeled "Replication."