What is Classic Load Balancer in AWS?

Key takeaways:

• AWS Classic Load Balancer (CLB) operates at the transport layer (TCP/UDP) based on IP addresses and ports.

• CLB distributes traffic across multiple targets, including EC2 instances and containers, enabling cross-zone load balancing.

• It supports health monitoring to route traffic only to healthy instances.

• CLB is cost-effective for low-traffic applications but lacks the advanced routing features of Application Load Balancer (ALB).

• CLB is suitable for simple applications with basic load balancing needs.

• Efficient traffic distribution requires roughly equal instances in each availability zone.

An AWS load balancerA load balancer is a device or software that distributes incoming network traffic across multiple servers or resources to ensure no single server becomes overwhelmed. By spreading the traffic evenly, load balancers help maintain the availability, reliability, and performance of applications and websites, especially during high-traffic periods. They can also reroute traffic to healthy servers if one fails, ensuring continuous service. Load balancers are commonly used in cloud computing and large-scale web applications to manage traffic efficiently and provide fault tolerance. routes incoming traffic across multiple targets within different Availability Zones, such as EC2 instances, containers, and IP addresses. Load balancers are used to direct incoming requests to multiple targets. The load balancer forwards requests based on request attributes to instances called targets. The number of resources behind a load balancer can be modified as per requirement without disrupting the application’s availability. 

Load balancers can be configured to accept incoming requests by specifying listeners. A listener process checks the connection requests based on the port and protocol specified during the load balancer’s configuration.

Classical Load Balancer

How does it work?

A Classic Load Balancer distributes incoming network traffic across multiple servers to ensure no single server is overwhelmed. A load balancer improves application reliability and performance by optimizing resource utilization and preventing server overload. It uses algorithms like round-robin, least connections, or IP hash to distribute incoming requests among backend servers. They monitor server health via health checks and route traffic based on predefined rules, ensuring efficient resource utilization and high service availability.

Ensuring that the number of registered instances in each availability zone is roughly equal is important. As a Classic Load Balancer distributes the network traffic across availability zones, if there are 12 instances in the Availability Zone us-east-2a and only three in us-east-2b. The traffic distribution will not be optimal.

It is important to ensure the number of instances in each availability zone is even for better traffic management. In the above case, the three instances in us-east-2b would handle the same amount of traffic as the ten instances in us-east-2a.

Quiz

Test your understanding of the AWS Classic Load Balancer with the quiz below.

Conclusion

In conclusion, AWS’s Classic Load Balancer (CLB) is an effective solution for distributing incoming traffic across multiple targets, such as EC2 instances and containers, within different availability zones.