Different types of load balancers and how they meet requirements for network design, high availability, and security

Can you explain the difference between Application Load Balancers (ALBs), Network Load Balancers (NLBs), and Classic Load Balancers (CLBs) in AWS?

Application Load Balancers operate at Layer 7 of the OSI model and are designed to handle advanced traffic routing for HTTP and HTTPS traffic, providing features like host and path-based routing. Network Load Balancers operate at Layer 4 and are optimized for low latency and high throughput, supporting TCP, UDP, and TLS traffic. They can handle millions of requests per second. Classic Load Balancers provide basic load balancing across multiple EC2 instances and operate at both the request level and connection level (Layer 7 and Layer 4).

How does an Application Load Balancer contribute to a secure network design?

An Application Load Balancer supports security features such as SSL/TLS decryption, which offloads this task from the backend servers, thus reducing their load. It also integrates with AWS WAF, providing centralized management of web application security policies that protect against common web exploits. Additionally, ALBs allow the creation of HTTPS listeners to use SSL/TLS protocols for secure data transmission.

What are the advantages of using Network Load Balancers for high availability in AWS network design?

Network Load Balancers are highly scalable and designed to handle volatile traffic patterns while providing high availability. They automatically distribute traffic across multiple availability zones (AZs) and scale up as traffic increases without any manual intervention. NLBs also provide a static IP that can be used as an Elastic IP or assigned to each AZ, which helps in maintaining the availability even in case of failure of a single AZ.

In what scenarios would you recommend using a Classic Load Balancer over the other types?

Classic Load Balancers might be recommended in scenarios where the user has an existing application running in the EC2-Classic network and requires simple load balancing of HTTP/HTTPS traffic or TCP traffic. It is also suitable for applications built within the EC2-Classic network where the user is not looking to use advanced routing features offered by newer load balancers.

How do load balancers in AWS integrate with Auto Scaling to ensure high availability?

Load balancers in AWS distribute incoming application or network traffic across multiple targets, such as Amazon EC2 instances. When these targets are part of an Auto Scaling group, the load balancer automatically adjusts the amount of traffic each instance receives based on the number of instances available, which the Auto Scaling group manages. This ensures that no single instance is overwhelmed, contributing to high availability.

What role do security groups play when configuring load balancers in AWS?

Security groups in AWS act as a virtual firewall for your instances to control inbound and outbound traffic. When configuring load balancers, you must assign security groups that specify which traffic is allowed to reach the load balancer and which traffic can leave it en route to the application servers. This is crucial for defining the permitted traffic for a secure architecture.

How can load balancers contribute to achieving zero downtime deployments in AWS?

Load balancers in AWS can contribute to zero downtime deployments by enabling rolling updates. During these updates, you can incrementally remove instances from the load balancer to update them to the new version and then add them back once the update is complete. This process ensures that at least a portion of your environment remains available to handle traffic at all times, avoiding downtime.

How does AWS ensure the availability of its load balancing services?

AWS ensures the high availability of its load balancing services by distributing the traffic across multiple availability zones. Each load balancer is designed to automatically detect unhealthy instances and reroute traffic to the healthy instances. They also offer redundancy by maintaining the operational capability if one or more availability zones face outages.

Can you describe how connection draining works with load balancers and its impact on service continuity?

Connection draining is a feature of load balancers that ensures in-flight requests are not dropped when instances are deregistered or become unhealthy. The load balancer stops sending new requests to the instance but keeps the existing connections alive until a specified timeout period, allowing in-flight requests to complete, thereby contributing to service continuity.

What is the purpose of cross-zone load balancing in an AWS Network Load Balancer and how does it enhance network design?

The purpose of cross-zone load balancing is to distribute traffic evenly across all registered instances in all enabled availability zones. This results in reduced latency because it prevents overloading a single instance and enhances fault tolerance and performance across multi-AZ deployments, leading to a more robust network design.

Describe a scenario where using a Network Load Balancer’s ability to handle millions of requests per second is critical?

A scenario that requires handling millions of requests per second is one in which a web application suddenly goes viral. For example, during an online sales event or the launch of a popular product, there could be a sudden and massive surge in traffic. In such a case, a Network Load Balancer’s ability to scale rapidly is critical to accommodate the spike in traffic without any degradation in service.

How do AWS load balancers help protect applications from distributed denial-of-service (DDoS) attacks?

AWS Load balancers help protect applications from DDoS attacks by dispersing the traffic across multiple data centers within the AWS global network. The load balancers can absorb traffic spikes or unusual patterns, and when used in conjunction with AWS Shield and AWS WAF, they provide additional layers of protection by filtering malicious traffic and responding to such incidents.