While creating a new app pool, users are required to choose framework version and pipeline type. I was not sure about the difference between available pipeline types. I spent some time on this topic and reading MSDN articles. this is what I understood:
Classic Pipe Line in IIS 7.0
- Works just like IIS 6.0
- All requests pass through the IIS pipeline first, and then if the file extension is mapped to ASP.NET ISAPI extension, then the request is handed to aspnet_isapi.dll and passes through the ASP.NET request pipeline.
- If the file is static file, ASP or PHP, it is handled by something else.
Integrated Pipeline IIS 7.0
- Allows http modules to participate in all requests
- This works also for static contents, PHP pages and image
- Provides unified request processing, regardless of handler
- For example, managed Forms Authentication can be used for all content, including ASP pages, CGIs, and static files.