What is Kestrel and how does it differ from IIS

Kestrel and IIS (Internet Information Services) are both web servers used in the context of hosting and serving web applications, but they serve different purposes and have distinct characteristics:

1. Kestrel:

   • Definition: Kestrel is a cross-platform web server developed by Microsoft and used as the default web server for ASP.NET Core applications.
   • Features:
     • Cross-Platform: Kestrel can run on Windows, macOS, and Linux, making it versatile for hosting ASP.NET Core applications on various operating systems.
     • Performance: It is known for its high performance and efficiency, especially when handling a large number of concurrent connections.
     • Integration: While Kestrel can handle HTTP requests and responses efficiently, it is designed to work behind a reverse proxy server like IIS or Nginx for production scenarios.

2. IIS (Internet Information Services):

   • Definition: IIS is a web server developed by Microsoft specifically for Windows operating systems.
   • Features:
     • Windows Integration: IIS is tightly integrated with Windows Server and Windows desktop versions, providing a comprehensive feature set for hosting web applications.
     • Modules and Extensions: It supports a wide range of modules and extensions for various web technologies and services, such as ASP.NET, PHP, and others.
     • Management: It includes robust management tools (such as Internet Information Services (IIS) Manager) for configuring and managing web server settings.

Key Differences:

• Platform: Kestrel is cross-platform, while IIS runs exclusively on Windows.
• Purpose: Kestrel is designed primarily for hosting ASP.NET Core applications and is often used behind a reverse proxy server like IIS or Nginx in production scenarios. IIS, on the other hand, is a full-featured web server that supports various web technologies beyond ASP.NET Core.
• Performance vs. Features: Kestrel is lightweight and optimized for performance, particularly in handling high loads and concurrent connections. IIS offers a broader feature set and deep integration with Windows environments, making it suitable for a wide range of web hosting scenarios beyond just ASP.NET Core applications.

Usage in ASP.NET Core:

• In ASP.NET Core applications, Kestrel is typically used as the internal web server for development and can be used directly in production scenarios, often in conjunction with a reverse proxy server (like IIS or Nginx) for additional features and security.
• IIS can act as a reverse proxy server in front of Kestrel, handling tasks such as SSL termination, load balancing, and serving static files, while delegating dynamic content handling to Kestrel.

In summary, Kestrel and IIS serve different roles in hosting web applications: Kestrel as a lightweight, cross-platform web server optimized for ASP.NET Core, and IIS as a full-featured, Windows-specific web server supporting a broader range of web technologies and services.