51. Types of Load Balancers: Classic, Network and Application

Amazon Web Services (AWS) offers a variety of load balancing services, which are essential to the architecture of any distributed application. Load balancers distribute network or application traffic efficiently across multiple servers to ensure that no server is overloaded. This not only helps increase application availability and reliability, but also allows system administrators to efficiently manage network traffic for their applications. In this guide, we are going to discuss the three types of load balancers offered by AWS: Classic Load Balancer (CLB), Network Load Balancer (NLB), and Application Load Balancer (ALB).

Classic Load Balancer (CLB)

Classic Load Balancer is the original load balancing service from AWS. It provides load balancing of network (layer 4) and application (layer 7) traffic. CLB is ideal for applications that were built within the classic EC2 computing model. It distributes traffic to Amazon EC2 instances across multiple Availability Zones, which increases application fault tolerance.

The CLB supports listening for network traffic on TCP and SSL (Secure Sockets Layer) ports, as well as listening for application traffic on the HTTP port. It also supports SSL offloading, which allows the load balancer to be the endpoint for SSL connections and offloads the encryption and decryption work from EC2 instances.

Network Load Balancer (NLB)

Network Load Balancer is AWS' next generation load balancing service for network traffic. It operates at layer 4 (transport) of the OSI model, where it handles TCP, UDP, and TLS (Transport Layer Security) traffic. NLB is capable of handling millions of requests per second while maintaining ultra-low latencies, making it ideal for applications that require high performance and low latency.

One of the key features of NLB is its ability to preserve the client's original IP address, which is useful for applications that need to know the client's IP address for processing purposes. Additionally, NLB supports long-lived connections, which is ideal for WebSocket applications and streaming applications.

Application Load Balancer (ALB)

Application Load Balancer is an intelligent AWS load balancer for HTTP and HTTPS application traffic. It operates at layer 7 (application) of the OSI model, where it handles HTTP, HTTPS, HTTP/2 and WebSocket traffic. The ALB is designed for modern microservice-based applications such as containers and service-oriented applications.

One of the key features of the ALB is content-based routing, which allows the load balancer to direct traffic to different services in the back based on the content of the request. This is useful for microservices applications, where you can have different services that handle different parts of the application.

In addition, ALB supports SSL offloading, end-user authentication, URL redirection, HTTP request inspection, and integration with AWS WAF (Web Application Firewall), making it a powerful choice for modern web applications.

In conclusion, AWS offers a variety of load balancing services to meet different application needs. Classic Load Balancer is ideal for applications that were built within the classic EC2 computing model. Network Load Balancer is perfect for applications that require high performance and low latency. And Application Load Balancer is the best choice for modern applications based on microservices. By choosing the right load balancer for your application, you can ensure that your application is highly available and reliable, while efficiently managing network traffic.

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