Deploying .NET Core applications efficiently is critical for performance, security, and scalability. When hosting these applications, developers often choose between IIS (Internet Information Services) and Kestrel. Each deployment model has distinct advantages and trade-offs that impact web application performance, security, scalability, and management.
Kestrel Web Server Architecture
Kestrel is the default cross-platform web server included with .NET Core. It is designed to handle HTTP requests efficiently within application code, leveraging asynchronous programming to optimize performance.
Key Features of Kestrel:
- Cross-platform compatibility – Runs on Windows, Linux, and macOS.
- Lightweight and high-performance – Minimal overhead due to its modular architecture.
- Direct client communication – Eliminates intermediary layers, enhancing speed.
- Native async/await support – Optimized for modern .NET Core applications.
While Kestrel is highly efficient, it lacks some enterprise-grade features found in full-fledged web servers.
IIS Web Server Architecture
IIS is Microsoft’s mature web server solution, primarily designed for Windows environments. It provides extensive security, configuration, and scalability features essential for enterprise deployments.
Key Features of IIS:
- Enterprise-grade security – Integrated security features such as Windows Authentication and request filtering.
- Reverse proxy functionality – Acts as a proxy for Kestrel, enhancing security.
- Advanced configuration options – UI-based management through IIS Manager.
- Built-in load balancing – Facilitates scalability and high availability.
IIS enhances application stability and security but introduces additional overhead compared to Kestrel.
Performance and Scalability Comparison
Performance and scalability are critical considerations when selecting a deployment model.
Request Throughput
Kestrel outperforms IIS in raw request-handling capacity, making it ideal for high-performance applications. Benchmarks indicate that Kestrel processes 3x to 5x more requests per second than IIS in similar conditions.
However, IIS excels in handling enterprise workloads with its robust load balancing and process management.
Memory Usage
- Kestrel: Lower memory footprint due to its streamlined architecture.
- IIS: Higher memory usage but provides additional built-in capabilities such as caching and session management.
Application Density
- Kestrel: Maximizes app density on servers due to its lightweight nature.
- IIS: Supports shared framework hosting, optimizing multi-app deployment on Windows servers.
Security Considerations
Security is paramount when deploying business-critical applications.
Protocol Support
- Kestrel: Supports only HTTP(S) out-of-the-box.
- IIS: Supports additional protocols, including FTP, WebSockets, and SMTP.
SSL and Certificate Management
- IIS: Centralized certificate management with automated renewal options.
- Kestrel: Requires explicit configuration for SSL in each application.
Authentication and Access Control
- IIS: Supports Windows Authentication and Active Directory integration.
- Kestrel: Provides basic authentication, requiring custom implementation for advanced security needs.
Deployment and Management
Ease of deployment and management significantly affects maintenance overhead.
Operating System Compatibility
- IIS: Windows-only.
- Kestrel: Cross-platform (Windows, Linux, macOS).
Configuration and Administration
- IIS: Managed via IIS Manager UI and PowerShell.
- Kestrel: Requires CLI-based configuration and automation tools.
Monitoring and Diagnostics
- IIS: Integrates with Event Viewer and provides detailed logging.
- Kestrel: Relies on external tools like Application Insights for monitoring.
Typical Use Cases
The choice between IIS and Kestrel depends on the use case.
| Use Case | Recommended Server |
| High-performance microservices | Kestrel |
| Public-facing websites | IIS (with Kestrel as a reverse proxy) |
| Internal enterprise applications | IIS |
| Cloud-native applications | Kestrel |
Conclusion
Choosing between IIS and Kestrel depends on your application’s requirements. Kestrel excels in performance and cross-platform compatibility, while IIS provides enterprise-grade security and management features. For most production deployments, using IIS as a reverse proxy for Kestrel offers the best balance of security, scalability, and performance.