Professional Microsoft IIS 8

ISAPI Configuration

Internet Server Application Programming Interface (ISAPI) is a low-level programming interface that is used for running applications, such as ASP.NET, PHP, and Perl. Rather than being a server-side scripting technology, ISAPI is actually a true executable part of IIS. ISAPI applications run as .dlls and can be either extensions or filters. Extensions are applications that have access to the full functionality of IIS. Filters modify or augment the functionality of IIS. Filters check every request until one is found that needs to be processed. This check can be configured to examine either incoming or outgoing traffic. Some examples of ISAPI filters include authenticating and authorizing users, rewriting URLs, and modifying a response back to a client.

In IIS 8.0, ISAPI is being superseded by modules. Because of the integration of IIS 7.0 and ASP .NET, modules can now be written in either C++ or managed code and provide the same speed and security that only ISAPI applications once provided. ISAPI extensions and filters can still be used to provide for backward compatibility.

To run ISAPI applications on the server, two modules need to have the ISAPI information added. The ISAPI and CGI Restrictions module and the ISAPI Filters module both need to have the application information added in order for ISAPI to work. The ISAPI and CGI Restrictions module, shown in Figure 7.13, manages the ISAPI and CGI applications, adding descriptions and enabling or disabling the ...