Popular Load Balancers in AWS Explained Easily

Problem Statement

Amazon Web Services (AWS) offers several types of load balancers to distribute incoming network traffic across multiple resources like Amazon EC2 instances or containers. While we design Application and it’s Infrastructure components, we come across a stage where we need to Decide about the Load balancer to be used.


Here’s an easy explanation of four common popular types:


Application Load Balancer (ALB):

  1. Think of ALB as a smart traffic cop for web applications. – Can easily implement a Web Application Firewall WAF to protect against exploits.
  2. It operates at the application layer (Layer 7) and can route traffic based on content in the request, like URL paths or headers.
  3. Ideal for modern web applications, microservices, and API gateways.

Btw, What is Layer 7?

There are Seven Layers in the OSI Model (Open Systems Interconnection). Layer 7 is the topmost Application Layer and directly interacts with User applications. It includes HTTP, FTP and SMTP Protocols.

Network Load Balancer (NLB):

  1. NLB is like a high-speed traffic router for TCP and UDP traffic.
  2. It operates at the transport layer (Layer 4) and is highly scalable and performs well with ultra-low latency.
  3. Suited for handling massive amounts of connections or when you need to forward raw network packets.

Layer 4 – Wait, it’s again another Layer in OSI Model?

Yes, it is called a Transport Layer. It ensures end-to-end communication and data integrity between two devices on a Network. It includes TCP and UDP Protocols.

Classic Load Balancer (CLB):

  1. CLB is the older version and offers basic load-balancing capabilities.
  2. It balances traffic at both Layer 4 (TCP/UDP) and Layer 7 (HTTP/HTTPS).
  3. While still available, it’s generally recommended to use ALB or NLB for more advanced features and better performance.

Gateway Load Balancer (GWLB):

  1. It’s primarily used for scenarios where you need to distribute traffic across multiple network appliances, such as firewalls, intrusion detection systems (IDS), and other security or networking devices.
  2. GWLB is highly available, with redundancy built-in across multiple Availability Zones (AZs) to ensure fault tolerance.
  3. It helps improve network security by allowing you to integrate various security appliances and inspect traffic as it passes through.
  4. Just like other load balancers in AWS, GWLB uses target groups to direct traffic to specific resources. In this case, the resources are network appliances.

Suppose you have multiple security appliances, like firewalls and intrusion detection systems, in your network architecture to inspect incoming and outgoing traffic for threats. By placing a GWLB in front of these appliances, you can ensure that all traffic is evenly distributed across the security devices, helping you scale and secure your network effectively.

Remember, the choice of load balancer depends on your specific application’s needs. ALB is a popular choice for most modern web applications, NLB for high performance and scalability, and CLB may be used for simple scenarios.



Hope you Now know about the Load Balancers and wait for our Blog if you got lost by the terms referred to here as Protocols.

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