Description of the illustration twotierproxyarch.gif
This graphic has "Clients" on the left bounded by a dotted line. To its right is a "Firewall", and to its right is a column of two-sectioned boxes labeled "HTTP Server" and "Proxy plug-in". These boxes are clubbed together with the label "Web Servers (Web tier)". The dotted line including Web Servers (Web tier) and Firewall is labeled "DMZ". To the right of this column is a column of boxes labeled "Server/Object Cluster (presentation, object tiers)". Each box contains the labels "JSP", "Servlet", "EJB", and "JDBC". To the right of this column is a Database.
Clients point to each of the HTTP Servers through the Firewall. Each of the HTTP Servers points as a group with three arrows to each of the boxes in Server/Object Cluster (presentation, object tiers), and then to the Database.