Applications and Internet Information Services
A Web application could be a script within a single ASP page, a Java applet, or a custom application encompassing hundreds of Web pages. A given Web site can contain more than one Web application. Multiple Web applications are distinguished by the application's starting-point directory, or root directory, within the Web site. All the content within this directory and the directories below it are considered to be part of the Web application until another application starting point is encountered.
Server Development Technologies
Internet Information Services support multiple types of Web applications, including ASP, ISAPI, CGI, IDC, and SSI. Historically, the most common types of applications were Common Gateway Interface (CGI) applications and Perl scripts. Both of these technologies were created for use on UNIX-based Web servers. It wasn't until Microsoft created Internet Information Server in 1996 that these technologies became popular on a Windows NT computer and now on a Windows 2000 server.
As Internet Information Services has matured, so have the application technologies that it supports. With Internet Information Server, Microsoft introduced a new Web-based application technology called Internet Services Application Programming Interface (ISAPI). ISAPI (pronounced "I-sapi") was created exclusively for use on an Internet Information Services server. Then, with Internet Information Server 3, Microsoft introduced yet another technology called Active Server Pages (ASP). Today, ASP is the most widely used application technology on Internet Information Services 5.
Generally, the different applications can be distinguished by their file types, or file extensions. As a Web administrator, you will probably not be developing Web applications, but you will want to have a general knowledge of which type of applications your clients are running on your Web server. Following are the applications and their most common file extensions:
| Application Type | Common Extension |
|---|---|
| CGI | .exe |
| Perl | .pl |
| ISAPI | .dll |
| ASP | .asp |
Global versus Per Site Configuration
Most of the configuration discussed in this chapter can be configured either for an individual Web site or for all Web sites on the Internet Information Services server. To configure an individual Web site, simply right-click the Web site name within the Internet Information Services snap-in in the Microsoft Management Console (MMC), and then click Properties. Any configurations made within the properties of the individual site affect only that site.
To configure all Web sites at once, configure the master property sheets of the Internet Information Services server. To do this, right-click the computer name in the Internet Information Services snap-in, select WWW Service in the Master Properties list box, and click Edit. But, let me give you one note of warning here: If you configure an individual Web site, add a MIME mapping, and then configure and reapply the master properties, Internet Information Services will replace the individual site properties with the new master properties.
Web Application Manager (WAM)
Beginning with Internet Information Server 4, applications in Internet Information Services are processed by the Web Application Manager (WAM) that runs with Microsoft Transaction Server. This architecture of Internet Information Services was designed to provide a high level of performance for static, dynamic, and Web application content, while maintaining the reliability of Internet Information Services when running Web applications. Because static content doesn't affect the reliability of the Web server, all static requests are serviced immediately by InetInfo. This improves the performance of static content.
On the other hand, Web applications can run either in process or out of process. The definition of and difference between these states will be discussed in Chapter 13, "Performance Tuning and Reliability." Because of this flexibility, Web applications are managed by an internal object called the WAM. WAM itself is a Common Object Model (COM) component registered with Microsoft Transaction Server (MTS) and can be run in process or out of process. MTS, which is a run-time environment for COM components, hosts a WAM proxy object for each isolated process. Figure 7.1 shows how the WAM processes Web applications in Internet Information Services.
Figure 7.1. Internet Information Services creates one WAM for all in-process applications, one for the pooled applications, and individual WAMs for each out-of-process application.
When Internet Information Services receives a request for a Web application, the WAM determines whether the Web application is configured to run out of process. If so, the WAM forwards the request to an external MTS process. Otherwise, the request is completed in process with Internet Information Services. The WAM hosts all Web applications, whether they're in process or not, and controls loading and interfacing with ISAPI DLLs. During the installation of Internet Information Services, the IWAM_computername account is created. This is the Internet Information Services Web Application Manager identity and is used to start out-of-process Web applications in Internet Information Services.