There are two situations in which the Sun Java System Web Server plugin performs implicit URL rewriting:
When a response comes back from the Sun Java System Web Server. If implicit URL rewriting has been chosen, the plugin rewrites the URLs in the response before passing the response to the client.
When the request given by a client need not be sent to the Sun Java System Web Server and can be served on the web server side. Such requests may occur in the middle of a session and the response may need to be rewritten.