
This also means that an ASP.NET request must pass through authentication and authorization modules in both process models. The ASP.NET processing pipeline is separate from the IIS 7 and later processing pipeline, and the ASP.NET request processing pipeline features are not available to other resource types. In this mode, requests are processed initially through IIS 7 and later modules, and ASP.NET requests are further processed by the aspnet_isapi.dll.

You can run as many application pools on your IIS 7 and later server as you need, though this can affect server performance.

You can choose to use the default application pool provided by IIS on install, or you can create your own application pool. Application pools significantly increase both the reliability and manageability of your Web infrastructure. Process boundaries separate each worker process therefore, application problems in one application pool do not affect Web sites or applications in other application pools. Because application pools allow a set of Web applications to share one or more similarly configured worker processes, they provide a convenient way to isolate a set of Web applications from other Web applications on the server computer. An application pool defines a group of one or more worker processes, configured with common settings that serve requests to one or more applications that are assigned to that application pool. The element contains configuration settings for all application pools running on your Internet Information Services (IIS) 7 or later server.
