Multi-Tier Proxy Architecture Proxy Architecture Benefits Proxy Architecture Limitations

Cluster Architectures 9-11

9.4.2 Multi-Tier Proxy Architecture

You can also use a bank of Web servers as the front-end to a pair of WebLogic Server clusters that host the presentation and object tiers. This architecture is shown in Figure 9–5 , below. Figure 9–5 Multi-Tier Proxy Architecture This architecture provides the same benefits and the same limitations as the Section 9.3, Recommended Multi-Tier Architecture. It differs only insofar as the Web tier is placed on a separate bank of Web servers that utilize WebLogic proxy plug-ins.

9.4.3 Proxy Architecture Benefits

Using standalone Web servers and proxy plug-ins provides the following advantages: ■ Utilize Existing Hardware If you already have a Web application architecture that provides static HTTP content to clients, you can easily integrate existing Web servers with one or more WebLogic Server clusters to provide dynamic HTTP and clustered objects. ■ Familiar Firewall Policies Using a Web server proxy at the front-end of your Web application enables you to use familiar firewall policies to define your DMZ. In general, you can continue placing the Web servers in your DMZ while disallowing direct connections to the remaining WebLogic Server clusters in the architecture. The figures above depict this DMZ policy. 9-12 Using Clusters for Oracle WebLogic Server

9.4.4 Proxy Architecture Limitations

Using standalone Web servers and proxy plug-ins limits your Web application in the following ways: ■ Additional administration The Web servers in the proxy architecture must be configured using third-party utilities, and do not appear within the WebLogic Server administrative domain. You must also install and configure WebLogic proxy plug-ins to the Web servers in order to benefit from clustered servlet access and failover. ■ Limited Load Balancing Options When you use proxy plug-ins or the HttpClusterServlet to access clustered servlets, the load balancing algorithm is limited to a simple round-robin strategy.

9.4.5 Proxy Plug-In Versus Load Balancer