Posted: Jun. 10, 2002

IIS 5 Isolation Mode runs most processes in the IIS Administration Service.

Just as with IIS 6.0's native Worker Process Isolation Mode (see the illustration "IIS 6 Architecture and Request Processing"), when an HTTP request arrives at the kernel-mode HTTP Listener, the validity of the request is checked. If the request is invalid, the appropriate HTTP error is immediately returned to the requester. If the request is valid, the HTTP Listener checks to see if it can handle the request from its cache. If the response is in the cache, the HTTP Listener sends the response immediately.

However, after this, the modes begin to differ substantially. IIS 5 Isolation Mode only has a single queue for HTTP requests, and all of the services in user mode (above the dotted line) function in the same fashion as they did in IIS 5.0. This means that Web applications typically run in the same process in the IIS Administration Service (INETINFO.EXE), or in an isolated process (DLLHOST.EXE). In addition, the Web Administration Service (WAS) only configures the HTTP Listener—it does not health-monitor processes or restart failing processes.