The external Internet contains the external clients, which communicate across the DMZ Firewall with the Load Balancer.
The Web Server Tier DMZ contains the Load Balancer, which communicates with the OracleAS Single Sign-On and OC4J for Single Sign-on servers, as well as with Oracle Web Cache. The Web Server Tier DMZ also contains the J2EE servers, the Web Cache and Oracle HTTP Server, and the Infrastructure DMZ.
Within the Web Server Tier DMZ:
The Infrastructure DMZ contains Real Application Clusters, the OracleAS Metadata Repository, including product metadata, management metadata, and security metadata, and Oracle Internet Directory. Oracle Internet Directory communicates across the Infrastructure Firewall using SQL*Net. It communicates with the Oracle HTTP Servers in the Web Server Tier DMZ.
The J2EE Business Logic DMZ contains J2EE without Web Cache. J2EE communicates using AJP with Oracle HTTP Server in the Web Server Tier DMZ.
The corporate intranet contains the customer database with business data, possibly in Real Application Clusters or a cold failover cluster. The customer database communicates using AJP with the J2EE servers in the Webserver Tier DMZ. It also communicates using SQL*Net with mod_plsql in the Webserver Tier DMZ.