The architecture of IIS (Internet Information Services) involves several components and layers working together to process web requests and serve web content. Here's an overview of the key components and their roles in the IIS architecture:
1. HTTP.sys: At the core of IIS architecture is the HTTP.sys kernel-mode driver. It acts as a listener for incoming HTTP requests and handles low-level HTTP protocol functionality. HTTP.sys intercepts requests and routes them to the appropriate IIS components.
2. Application Pools: An application pool is a logical grouping of websites or applications within IIS. Each application pool runs in its own worker process (w3wp.exe) and provides isolation and resource management. Application pools ensure that a failure in one application doesn't affect others and allow for granular configuration of settings like .NET framework version, identity, and recycling options.
3. Worker Processes (w3wp.exe): Worker processes are responsible for executing web applications within IIS. Each application pool has its own worker process, which hosts the web applications and manages their lifecycle. Worker processes handle the processing of requests, execute server-side code, and generate responses.
4. Modules and Handlers: IIS uses modules and handlers to extend its functionality and process requests. Modules are components that can be added or removed to perform specific tasks in the request/response pipeline. Examples include URL rewriting, authentication, compression, and caching modules. Handlers are responsible for executing code for specific request types, such as ASP.NET requests.
5. Configuration Store: The IIS configuration store stores the configuration settings for IIS, including information about websites, application pools, modules, and more. It can be stored in various locations, such as the registry or XML files. The configuration store allows administrators to define how IIS behaves and controls its various features.
6. Web Content: The actual web content, including static files (HTML, CSS, images) and dynamic content (ASP.NET pages, PHP scripts, etc.), resides on the server's file system or is fetched from databases or other systems. IIS serves this content to clients in response to their requests.
7. Logging and Diagnostics: IIS includes logging and diagnostic features that capture information about requests, errors, and performance. This data can be useful for troubleshooting, monitoring, and analyzing the server's behavior.
8. Security and Authentication: IIS provides various security features, such as SSL/TLS encryption, authentication methods (e.g., Windows Authentication, Forms Authentication), and authorization rules. These features help protect web applications and ensure secure communication between clients and the server.
9. Management Tools: IIS provides graphical and command-line tools, such as Internet Information Services (IIS) Manager and PowerShell cmdlets, for managing and configuring IIS settings, websites, application pools, and other components.
The architecture of IIS is designed to handle incoming web requests, process them through various modules and handlers, execute server-side code, and serve the appropriate content back to clients. Its modular nature allows for extensibility and customization, enabling developers and administrators to tailor IIS to their specific requirements.