Application pool in IIS

It defines a group of one or more worker processes, configured with common settings that serve requests applications that are assigned to that application pool. It allow a set of Web applications to share one or more similarly configured worker processes and provide a convenient way to isolate a set of Web applications from other set of Web applications on the server computer. In it there is are process boundaries which separate each worker process and because of this reason application problems in one application pool do not affect Web sites or applications in other application pools.

 

1) Integrated mode

2) Classic mode

 

1) Integrated mode

When a worker process in an application pool receives a request, the request passes through an ordered list of events. Each event calls the necessary native and managed modules to process portions of the request and to generate the response.There are several benefits to running application pools in Integrated mode. First the request-processing models of IIS and ASP.NET are integrated into a unified process model. This model eliminates steps that were previously duplicated in IIS and ASP.NET, such as authentication. Additionally, Integrated mode enables the availability of managed features to all content types.

 

2) Classic mode

It uses the IIS 6.0 processing pipeline for hosting ASP.NET applications. In this mode, requests are processed initially through IIS 7 and later modules, and ASP.NET requests are further processed by the asp.net_isapi.dll. 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. This also means that an ASP.NET request must pass through authentication and authorization modules in both process models. While this is not as efficient as Integrated mode, it does allow you to run applications developed using ASP.NET version 1.1 on an IIS 7 and later server without modifying the application to run in Integrated mode.