Know the Differences between ALB and NLB

In cloud computing, ALB and NLB are significant in distributing incoming traffic to maintain optimal performance and reliability. ALB specializes in intelligent routing at the application layer to distribute the traffic uniformly.

NLB, the Network Load Balancer, focuses on high-speed, low-latency traffic handling at the network layer.

In this blog, we'll discuss the unique strengths of these two tools, exploring their differences to help you make an informed choice.

So, let's get started!

Revisiting Load Balancers

Load balancers can be considered the backbone for seamless, efficient application delivery.

They are intelligent traffic managers that ensure that incoming requests are efficiently distributed across multiple servers. This prevents overloading, ensuring seamless user experiences.

Load balancers act as gatekeepers that balance the load, enhancing scalability, fault tolerance, and overall application performance.

They employ various algorithms to distribute the traffic, such as round-robin, least connections, IP hash, and more. These algorithms consider server health, availability, and performance to make intelligent routing decisions.

This dynamic balancing of requests helps prevent any single server from being overwhelmed, ultimately improving the overall performance and availability of the application.

Also Read: Differences between Blue-Green and Canary

Types of Load Balancer in AWS

1. Classic Load Balancer (CLB)

The Classic Load Balancer is the original load balancer provided by AWS. It operates at the network stack's application and transport layers, making it suitable for a wide range of applications.

CLB supports both HTTP and TCP traffic, providing basic load-balancing capabilities. However, it lacks some advanced features and flexibility in newer load balancer types.

2. Application Load Balancer (ALB)

The Application Load Balancer, also known as ALB, is designed to route and balance HTTP and HTTPS traffic at the OSI model's application layer (Layer 7).

ALB offers advanced features, including content-based routing, path-based routing, host-based routing, and support for WebSockets.

It is well-suited for modern application architectures such as microservices and container-based deployments.

3. Network Load Balancer (NLB)

The Network Load Balancer, or NLB, operates at the transport layer (Layer 4) of the OSI model, making it capable of handling massive traffic volumes with extremely low latency.

NLB is highly scalable and provides high-performance load balancing for TCP, UDP, and TLS traffic.

It is ideal for applications that require ultra-high performance, such as gaming, media streaming, and IoT scenarios.

What is Application Load Balancer (ALB) vs Network Load Balancer (NLB)?

ALB is all about smart routing. It analyzes HTTP headers, URL paths, and hostnames to make intelligent decisions about where to send incoming traffic.

With ALB, you get advanced features like content-based and path-based routing, perfect for modern application architectures, and fine-grained control over traffic.

On the other hand, NLB is a powerhouse that operates at the network layer 4. It's a traffic-handling beast optimized for high-volume, low-latency performance.

NLB easily handles TCP, UDP, and TLS traffic, making it an excellent choice for applications that demand extreme scalability and blazing-fast response times.

Also Read: AWS Cost Optimization Best Practices & Tools

1. NLB vs ALB - Protocols Followed

NLB primarily operates at the transport layer (Layer 4) of the OSI model and supports TCP (Transmission Control Protocol), UDP (User Datagram Protocol), and TLS (Transport Layer Security) protocols.

This makes it suitable for a wide range of network-based applications that require high-performance and low-latency traffic handling.

On the other hand, ALB operates at the application layer (Layer 7) and supports protocols like HTTP (Hypertext Transfer Protocol) and HTTPS (HTTP Secure).

ALB analyzes the application-level data, such as HTTP headers, URL paths, and hostnames, to make intelligent routing decisions. It also supports WebSockets, allowing bidirectional communication between clients and servers.

Also Read: Differences between EBS, S3, and EFS in AWS

2. ALB vs. NLB - OSI Layer

ALB functions at the OSI model's application layer (Layer 7).

It deeply inspects the application-level data, such as HTTP headers, URL paths, and hostnames, to make intelligent routing decisions.

ALB is specifically designed to handle HTTP and HTTPS traffic, offering advanced features like content-based routing, path-based routing, and support for WebSockets.

With ALB, you have granular control over application-level routing.

NLB, on the other hand, operates at the transport layer (Layer 4) of the OSI model.

It focuses on efficient traffic distribution without inspecting the application-level data. NLB supports protocols such as TCP (Transmission Control Protocol), UDP (User Datagram Protocol), and TLS (Transport Layer Security).

It excels at high-performance, low-latency traffic handling, making it an excellent choice for network-based applications that require fast and reliable communication.

3. NLB vs. ALB - Traffic Routing & Routing Algorithm

NLB primarily focuses on network-level traffic routing. It uses a flow-based routing mechanism, which means that once a connection is established, subsequent packets of that connection will follow the same route.

This enables efficient handling of TCP, UDP, and TLS traffic, making NLB suitable for applications requiring high-performance and low-latency network communication.

ALB, on the other hand, excels at application-level traffic routing. It uses advanced routing algorithms based on content-based, path-based, and host-based routing.

ALB intelligently inspects the application-level data, such as HTTP headers, URL paths, and hostnames, to determine the most appropriate backend server to handle each request.

This allows for flexible and granular control over routing decisions, making ALB ideal for applications with complex routing requirements, such as microservices architectures.

4. ALB vs. NLB - Static IP

With ALB, static IP addresses are not natively supported. ALB is designed to scale dynamically based on traffic demands, and as a result, it does not provide a fixed, static IP address that you can rely on.

Instead, ALB is assigned a constant DNS name, and the underlying IP addresses associated with the DNS name may change dynamically as the load balancer scales in or out.

On the other hand, NLB provides support for static IP addresses. When you create an NLB, you can assign an Elastic IP address, which remains fixed and does not change over time.

This provides a stable endpoint for your applications to communicate with, regardless of scaling events or changes to the backend servers.

5. ALB vs. NLB - Targets

ALB can handle a higher number of targets compared to NLB. It supports thousands of targets per load balancer, allowing you to distribute traffic across many instances or containers.

ALB is well-suited for applications with dynamic scaling needs or those built on microservices architectures that require many backend targets.

Whereas NLB supports a smaller number of targets per load balancer.

While NLB can still handle many targets, it is generally designed for applications that require extreme scalability, high network throughput, or specialized network protocols.

NLB is ideal for scenarios like gaming servers, media streaming, or IoT devices.

Also Read: Top Monitoring & Testing Tools for Microservices

6. NLB vs. ALB - EndPoint Services

NLB supports endpoint services through its integration with AWS PrivateLink.

With NLB, you can create endpoint services that expose your applications privately over Amazon VPC (Virtual Private Cloud) without requiring public IP addresses.

This enables secure and private communication between services within your VPC or across different VPCs. NLB's integration with PrivateLink provides a seamless way to securely expose your applications to other services or customers.

ALB does not natively support endpoint services through PrivateLink. ALB is primarily designed to handle application-level traffic routing and load balancing, focusing on HTTP and HTTPS protocols.

While ALB can expose applications publicly over the internet, it does not have the same level of native integration with PrivateLink for private endpoint services.

7. ALB vs NLB - Performance & Latency

ALB is designed to provide advanced application-level routing and offers additional features like content-based routing and WebSockets support.

It operates at the OSI model's application layer (Layer 7) and performs deep packet inspection to make intelligent routing decisions.

While ALB can handle high-traffic loads efficiently, its performance may be slightly lower than NLB due to the additional processing required for application-level analysis.

NLB excels in providing high-performance, low-latency traffic handling. It operates at the OSI model's transport layer (Layer 4) and focuses on efficiently distributing network-level traffic.

NLB is designed to handle extreme scalability and high network throughput, making it an excellent choice for applications that require fast and reliable communication, such as gaming servers or media streaming platforms.

NLB's optimized architecture results in lower latency than ALB, allowing for near-instantaneous response times.

8. ALB vs NLB - Costs

ALB pricing is based on several factors, including the number of load balancer instances, the number of processed bytes, and the number of active connections.

You pay for the ALB resources provisioned and the data transferred through the load balancer. ALB also offers a free tier for new customers to get started without additional costs.

NLB pricing is also based on the number of load balancer instances, the number of processed bytes, and the number of active connections.

Similar to ALB, you pay for the NLB resources provisioned and the data transferred through the load balancer. NLB also provides a free tier for new customers to help them get started.

NLB vs. ALB - Use Cases

Use Cases of NLB

• High-performance applications: NLB is ideal for applications requiring extreme scalability and high network throughputs, such as gaming platforms or streaming services.

• IoT applications: NLB's ability to handle high volumes of traffic and low latency makes it suitable for IoT applications that involve real-time data processing and communication.

• Network-intensive workloads: NLB is well-suited for applications that heavily rely on network traffic, such as video transcoding or data replication services.

Use Cases of ALB

• Web applications: ALB is perfect for applications requiring advanced routing capabilities and flexible traffic management based on application-level data.

• Microservices architectures: ALB's support for content-based routing and path-based routing makes it a natural choice for microservices architectures, allowing for granular control over traffic distribution.

• Container-based deployments: ALB integrates well with container orchestration platforms like AWS ECS (Elastic Container Service) and Kubernetes, providing efficient load balancing for containerized applications.

NLB vs ALB - Kubernetes Specific Differences

In a Kubernetes environment, NLB can be used as an external load balancer for Kubernetes Services of "LoadBalancer ".

When you create a Kubernetes Service with the type set to "LoadBalancer" and use NLB, it automatically provides an NLB in the AWS environment.

NLB assigns a stable IP address as the external endpoint for the Kubernetes Service, allowing external traffic to be balanced across the Kubernetes Pods.

ALB is not natively supported as an external load balancer for Kubernetes Services. However, you can still leverage ALB in AWS by integrating it with Kubernetes through an Ingress Controller.

An Ingress Controller bridges ALB and Kubernetes, routing incoming traffic to the appropriate Kubernetes Services based on rules defined in Kubernetes Ingress resources.

This enables advanced application-level routing and traffic management provided by ALB within the Kubernetes environment.

Also Read: Difference between Service Meshes - Consul, Istio, and Linkerd

When to Use ALB vs NLB & Why?

When deciding between ALB (Application Load Balancer) and NLB (Network Load Balancer), it's important to consider your application's specific requirements and the features each load balancer offers.

Here are some factors to consider while choosing load balancers for your org.

1. Traffic Handling

If your application requires high network performance, low latency, and extreme scalability, NLB is a better choice.

NLB excels at handling network-level traffic and is ideal for scenarios such as gaming servers, media streaming, or IoT applications.

2. Application-Level Routing

ALB is the preferred option if your application requires advanced application-level routing and traffic management.

ALB offers features like content-based routing, path-based routing, and support for WebSockets, making it suitable for modern application architectures and microservices deployments.

3. Protocols and Traffic Types

Consider the protocols and traffic types your application needs to handle.

NLB supports TCP, UDP, and TLS traffic, while ALB specializes in handling HTTP and HTTPS traffic. Choose the load balancer that aligns with your specific protocol and traffic requirements.

4. Flexibility and Control

ALB provides greater flexibility and control over traffic routing and management compared to NLB.

If your application requires fine-grained control over routing decisions, ALB's advanced routing capabilities make it a suitable choice.

5. Cost Considerations

Evaluate the cost implications of each load balancer based on your expected traffic volume, data transfer, and usage patterns.

NLB generally offers a more cost-effective solution for high-traffic scenarios, while ALB provides additional features at a potentially higher cost.

Also Read: Differences between ECS and Open-Source Kubernetes

Limitations of ALB and NLB

ALB Limitations

• Limited to Layer 7: ALB operates at the OSI model's application layer (Layer 7), which means it is specifically designed for HTTP and HTTPS traffic. If your application requires load balancing for protocols other than HTTP(S), ALB may not be the most suitable choice.

• Less Scalability: Compared to NLB, ALB may have limitations regarding extreme scalability and high network throughput. While ALB can handle significant traffic loads efficiently, NLB is better suited for scenarios that demand extreme scalability and network performance.

• Lack of Static IP Support: ALB does not natively support static IP addresses. The underlying IP addresses associated with an ALB may change dynamically as the load balancer scales in or out. If your application requires a fixed, static IP address, ALB may not be the best option.

NLB Limitations

• Limited to Layer 4: NLB operates at the OSI model's transport layer (Layer 4), focusing on network-level traffic. While this is advantageous for high-performance and low-latency scenarios, NLB lacks some advanced application-level routing features available in ALB.

• Complexity for HTTP(S) Traffic: NLB is not designed specifically for HTTP(S) traffic like ALB. While NLB can handle HTTP(S) traffic, advanced features such as content-based or path-based routing are not available, requiring additional configurations and components.

• Lack of WebSocket Support: NLB does not provide native support for WebSocket connections. If your application heavily relies on WebSocket communication, ALB is a more suitable choice with built-in WebSocket support.

ALB vs. NLB - Summary of Differences

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Frequently Asked Questions

When should I use the application load balancer vs. Network Load Balancer?

ALB for application-level routing and HTTP(S) traffic. NLB for high-performance network handling and scalability.

What is the advantage of NLB over ALB?

NLB offers high network performance, low latency, and extreme scalability, making it ideal for gaming servers, media streaming, and IoT applications.

What are the 3 types of load balancers in AWS?

Three types of load balancers in AWS:

• Classic Load Balancer (CLB)

• Application Load Balancer (ALB)

• Network Load Balancer (NLB)

Can we use ALB and NLB together?

Yes, ALB and NLB can be used together in an AWS architecture. They serve different purposes and can complement each other in complex application deployments.

How to AWS Pass traffic from NLB to an ALB?

Use AWS Global Accelerator to direct traffic from NLB to ALB.

Further Reading