| There are various options for how to build the combined WAS and Domino system. These options differ mainly in what functions the WAS and Domino servers take on and where they are placed in the usual tiered network configuration. A common network configuration for providing a Web application to Internet users consists of three tiers (or layers or zones), each separated by firewall systems. The Internet facing tier is often referred to as the "demilitarized zone," or DMZ, and usually consists of load balancing or authentication systems. Web and application servers sit in a zone behind the DMZ, and data servers in a "data layer" behind that. The multi-tiered configuration provides increasing security protection from the DMZ through the data layer. The server systems are placed within the tiers according to security and inter-system performance considerations. Depending on the roles they play, WAS and Domino usually sit in either of the two network tiers behind the DMZ. As a Web application server (for servlets, JSPs, or Web services), WAS is often located in the application zone. When WAS serves primarily as an EJB container, it is placed in the data layer, so as to be close to (or co-resident with) the database server. Domino used as an HTTP server can be placed in the application zone (or even DMZ if necessary). However, it is most common to find Domino in the data layer being used as a data or document repository or collaboration server. In a production application environment, it is most often the case that WAS and Domino are installed on separate computers. This is done simply to allow the WAS and Domino systems to be placed in separate network tiers. It is also done for scalability and performance reasons and to make system management easier. Although with more sophisticated hardware platforms, it is possible to have all system components installed on one physical system, for example using hardware partitioning to create separate server images on a single system. In some cases, such as for development or testing, it is convenient to install Domino and WAS on a single computer. The steps for installing Domino and WebSphere on the same computer are basically the same as for separate computers, although there are some simplifications in the install procedure when both applications share the same hardware platform. Those simplifications are described in the configuration and setup details given later in this chapter and in Appendix C. |
