What is AWS Network Load Balancer?

An AWS load balancer routes incoming traffic across multiple targets within different Availability Zones, such as EC2 instances, containers, and IP addresses. Load balancers are important in cloud computing, especially for applications that require high throughput and low latency. Load balancers direct incoming traffic based on the request attributes to instances called targets. The instances that serve as targets form a logical grouping called a target group.

AWS Load Balancer uses listeners to assess the incoming requests and forward them to targets. Listeners use rules to evaluate incoming requests.

A Network Load Balancer (NLB) is a type of AWS load balancer that works at the transport layer of the OSI model. It distributes the incoming network traffic to multiple targets based on the rules. NLBs are designed to manage the high number of requests per second, which is essential for applications that require high throughput and low latency. As an NLB receives a request, it verifies against the rules and then opens a connection with the target, therefore evaluating the request at the network level to ensure high availability. The request is only forwarded if healthy targets are available.

Let’s have a look at how NLB works:

Why do we need an NLB?

Let’s consider a popular online streaming service like Netflix. They have a massive amount of users streaming movies and TV shows at any given time. To ensure everyone gets a smooth experience, Netflix uses AWS NLB. NLB operates at the Transport layer, which manages the data flow well. It evaluates the connections coming in and out.

As a new viewer decides to watch a show, it sends a request to Netflix. The request goes to the NLB first. The NLB checks its rules and looks at all the healthy targets available. It then establishes a connection between the viewer’s device and the chosen target. Before forwarding the request, NLB double-checks that the chosen target is healthy and ready to handle the request. It ensures that viewers are directed to targets in good shape and can deliver a smooth streaming experience. The viewer can enjoy their show, and because NLB makes sure they are sent to a server that isn’t overwhelmed, their streaming experience is fast and high-quality. If many people suddenly want to watch a popular new release, NLB notices the increase in traffic and adjusts, sending more viewers to different servers to balance the load.

Advantages of NLBs

High throughput and low latency: NLBs are optimized to handle many requests per second. This is crucial for applications, like online streaming services, that require fast response times and minimal delays.
Transport layer efficiency: Operating at the transport layer of the OSI model, NLBs excel at managing data flow. It makes intelligent decisions about which targets to send incoming requests to based on predefined rules. This ensures that requests are efficiently and reliably handled.
High availability and reliability: NLB evaluates incoming requests against its rules and only forwards them to healthy targets. This means that even if some targets are experiencing issues, NLBs redirect traffic to healthy ones. This ensures high availability and minimizes service disruptions.
Efficient resource utilization: NLBs ensure that resources are utilized efficiently by distributing traffic intelligently. This means servers aren’t overloaded while others remain underutilized, leading to cost-effective resource allocation.

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