Understanding AWS Load Balancers: ALB vs NLB vs GWLB

Load balancers are crucial components in modern cloud architecture, helping distribute traffic across multiple servers to ensure high availability and reliability. AWS offers three types of load balancers, each designed for specific use cases. In this article, we'll deep dive into their differences and when to use each one.

Prerequisites

Before we dive into the specifics of AWS load balancers, let's understand two fundamental concepts:

1. What is a load balancer?

2. How does network traffic flow through the OSI model?

Understanding Load Balancers

Imagine you've developed a game application deployed on a single EC2 instance. Initially, with five users, everything works fine. However, as your game becomes popular and hundreds of users try to access it simultaneously, a single instance can't handle the load, resulting in:

• Application slowness

• Potential downtime

• Poor user experience

This is where load balancers come in. By deploying multiple EC2 instances and placing a load balancer in front of them, you can:

• Distribute traffic evenly across instances

• Handle increased user load

• Ensure high availability

• Provide better user experience

The OSI Model and Traffic Flow

Network traffic flows through seven layers when traveling from client to server:

1. Layer 7 (Application Layer)

   • Handles HTTP/HTTPS protocols

   • Where applications interact with the network

2. Layer 6 (Presentation Layer)

   • Handles encryption/decryption

   • Manages SSL/TLS

3. Layer 5 (Session Layer)

   • Manages sessions between applications

   • Handles session tokens and authentication

4. Layer 4 (Transport Layer)

   • Breaks down data into smaller packets

   • Handles TCP/UDP protocols

5. Layer 3 (Network Layer)

   • Handles routing between networks

   • Manages IP addressing

6. Layer 2 (Data Link Layer)

   • Manages switches and physical addressing

   • Handles frame organization

7. Layer 1 (Physical Layer)

   • Deals with physical connections

   • Manages cables and hardware connections

AWS Load Balancer Types

1. Application Load Balancer (ALB)

Operating Layer: Layer 7 (Application Layer)

Key Features:

• HTTP/HTTPS traffic routing

• Path-based routing

• Host-based routing

• SSL/TLS termination

• Support for WebSocket and HTTP/2

Best For:

• Web applications

• Microservices

• Container-based applications

Considerations:

• More expensive than NLB

• Slightly higher latency

• More feature-rich for HTTP/HTTPS workloads

2. Network Load Balancer (NLB)

Operating Layer: Layer 4 (Transport Layer)

Key Features:

• Ultra-high performance

• Low latency

• Static IP support

• Sticky sessions

• TCP/UDP protocol support

Best For:

• Gaming applications

• Video streaming platforms

• Applications requiring extreme performance

• TCP/UDP based applications

Considerations:

• Less expensive than ALB

• Faster than ALB

• Cannot handle HTTP layer routing

• Perfect for streaming and real-time applications

3. Gateway Load Balancer (GWLB)

Operating Layer: Layer 3/4

Key Features:

• Designed for virtual appliances

• High security

• Encrypted packet handling

• Specialized traffic management

Best For:

• Firewall deployments

• VPN applications

• Security appliances

• Network virtual appliances

Considerations:

• Specific to virtual appliance deployments

• Offers enhanced security features

• Not suitable for standard web applications

How to Choose the Right Load Balancer

1. Choose ALB when:

   • You need HTTP/HTTPS routing

   • Your application requires path-based routing

   • You want to implement microservices architecture

   • Advanced routing rules are needed

2. Choose NLB when:

   • Ultra-low latency is crucial

   • You need static IP addresses

   • You're building gaming or streaming applications

   • TCP/UDP protocol support is required

3. Choose GWLB when:

   • Deploying virtual security appliances

   • Implementing firewalls or VPN solutions

   • High-security packet encryption is needed

   • Working with network virtual appliances

Conclusion

Understanding the differences between AWS load balancers is crucial for architecting robust and efficient applications. While ALB excels at HTTP/HTTPS routing and features, NLB provides ultra-fast performance for TCP/UDP workloads, and GWLB specializes in virtual appliance deployments. Choose the right load balancer based on your specific use case and requirements.

Tags

#AWS #CloudComputing #DevOps #LoadBalancing #TechnicalArchitecture

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This article is part of AWS DevOps Zero to Hero series. Follow for more cloud and DevOps content.