ASP.NET Architecture on Windows Server 2003

On Windows Server 2003, the architecture changes because IIS 6 allows multiple processes to be used to host separate Web applications. This is shown in Figure 20.2.

Figure 20.2: ASP.NET architecture on Windows Server 2003 with IIS 6

Note  

IIS 6 supports a backwards compatibility mode that, in turn , supports the IIS 5 ASP.NET worker process model.

Compared to the ASP.NET architecture under Windows 2000, the primary difference in Windows Server 2003 is that separate IIS worker process instances (W3wp.exe) can be used to host Web applications. By default, these run using the NT Authority\NetworkService account, which is a least privileged local account that acts as the computer account over the network. A Web application that runs in the context of the Network Service account presents the computer's credentials to remote servers for authentication.

Configuring ACLs for Network Service

Configuring an access control list (ACL) for the Network Service account varies for local and remote machines. If you want to grant access to the Network Service account on the local machine, add the Network Service account to an ACL. If you want to grant access to the Network Service account on a remote machine, add the DomainName\MachineName$ account to an ACL.

Note  

Do not confuse the Network Service account with the Network built-in group , which includes users who were authenticated across the network.

The main components of the architecture depicted by Figure 20.2 are summarized in Table 20.3.

Table 20.3: Components of the Windows Server 2003 ASP.NET Architecture

Component	Description
Aspnet_isapi.dll	Queues requests for processing by the managed code ASP.NET engine and performs health monitoring.
Aspnet_filter.dll	A lightweight ISAPI filter used only to support cookie-less session state for ASP.NET applications. Runs inside W3wp.exe.
W3wp.exe	The IIS worker process that contains the managed code ASP.NET processing engine. The URL space can be arbitrarily divided among different W3wp.exe instances using IIS 6 application pools. A Web garden mode is also supported. Requests are routed to the W3wp.exe process instance directly from Http.sys which runs in kernel mode. By default, the process runs under the Network Service account but can be configured.
Aspnet_state.exe	An optional Windows service used to store session state for ASP.NET applications. It can run on the Web server or on a remote machine (required for Web farm scenarios). Runs under the Network Service account but can be configured using the Services snap-in.