Web clients request service from applications. They make their requests to Web servers. If a requested application resides on an application server remote to a Web server, the Web server must use a servlet redirector to relay the request to the remote application server.
The servlet redirector is available in these varieties:
Section 7.1.3.* compares the servlet redirector options, as well as some additional configurations for accomplishing a separation of Web servers from application servers.
When a Web server and application server handling servlet requests reside on the same machine, it is not necessary to use a servlet redirector.