WebSphere Application Server V7.0: Concepts ... - IBM Redbooks

5.2.4 Web servers and WebSphere Application Server Plug-in
Most WebSphere Application Server topologies will have a Web server which
receives HTTP-based requests from clients. For security reasons the Web server
should be placed in a separate network zone secured by firewalls (a DMZ).
Usually the Web server, in conjunction with the WebSphere Application Server
Plug-in, provides the following functionality in the topology:
► Serves requests for static HTTP content like HTML files, images, and so forth.
► Requests for dynamic content like Java Server Pages (JSPs), servlets, and
portlets are forwarded to the appropriate WebSphere Application Server
through the WebSphere Application Server Plug-in.
► Allows caching of response fragments using the Edge Side Include (ESI)
cache.
► Breaks the secured socket layer (SSL) connection from the client (unless this
is done by another device in the architecture) and optionally opens a separate
secured connection from the Web server to the Web container on the
application server system.
WebSphere Application Server comes with Web server plug-ins for all supported
Web servers.
Note: For information about Web servers supported by WebSphere
Application Server V7.0, organized by platform, refer to the following Web
page:
http://www-01.ibm.com/support/docview.wss?rs=180&uid=swg27012369
The plug-in uses a configuration file (plugin-cfg.xml) that contains settings
describing how to pass requests to the application server. The configuration file
is generated on the application server. Each time a change on the application
server affects the request routing of requests (for example, a new application is
installed) the plug-in must be regenerated and propagated to the Web server
machine again.
Note: In a stand-alone topology, only unmanaged Web servers are possible.
This means the plug-in must be manually pushed out to the Web server
system. The exception to this is if you are using IBM HTTP Server. The
application server can automatically propagate the plug-in configuration file to
IBM HTTP Server, even though it is an unmanaged node, by using the
administrative instance of IBM HTTP Server.
Chapter 5. Topologies 137