Choosing the Right Load Balancer: Application vs. Network Load Balancing Explained

I can provide you with an explanation of the differences between an Application Load Balancer (ALB) and a Network Load Balancer (NLB) in the context of AWS, as well as their equivalents in other cloud providers.

Amazon Web Service (AWS):

• Application Load Balancer (ALB): An ALB operates at the request level (Layer 7) of the OSI model, routing traffic based on HTTP/HTTPS headers and content. It’s designed to handle dynamic content and advanced routing, such as path-based and host-based routing, as well as support for WebSockets and HTTP/2. ALB also supports SSL/TLS termination, providing additional security for your applications.
• Network Load Balancer (NLB): An NLB operates at the connection level (Layer 4) of the OSI model, routing traffic based on IP protocol data. It’s designed for high-performance, low-latency applications and can handle millions of requests per second. NLB preserves the source IP address of the client, which allows back-end servers to see the originating client’s IP address. It also supports long-lived TCP connections, making it suitable for real-time applications like gaming and IoT.

Google Cloud Platform (GCP):

• HTTP(S) Load Balancing: This is the equivalent of AWS ALB. It operates at the Layer 7 of the OSI model and provides advanced request-based routing, SSL/TLS offloading, and support for WebSocket and HTTP/2.
• TCP/SSL Proxy Load Balancing: This is the equivalent of AWS NLB. It operates at the Layer 4 of the OSI model and supports high-performance, low-latency applications with TCP and SSL passthrough capabilities.

Microsoft Azure:

• Azure Application Gateway: This is the equivalent of AWS ALB. It operates at the Layer 7 of the OSI model and offers features like SSL/TLS offloading, advanced routing based on HTTP/HTTPS headers, and support for WebSocket and HTTP/2.
• Azure Load Balancer: This is the equivalent of AWS NLB. It operates at the Layer 4 of the OSI model and provides high-performance, low-latency load balancing for TCP and UDP traffic, as well as direct server return (DSR) to maintain the client’s source IP address.

In summary, the primary difference between an Application Load Balancer and a Network Load Balancer is the layer of the OSI model they operate on, with ALBs providing more advanced routing capabilities based on request content and NLBs focusing on high-performance, low-latency applications with simple IP-based routing.