Difference Between Application Load Balancer and Network Load Balancer

In this cloud world, picking the right tools keeps your apps running smooth and fast. If you work with AWS, you likely face choices on how to spread traffic across servers. That’s where load balancers come in. This guide dives into the difference between application load balancer and network load balancer. These two AWS options handle traffic differently, based on your needs like speed, routing smarts, or protocol support. Developers, architects, and learners often weigh these to build strong systems. Let’s break it down step by step so you can decide confidently.

Understanding Load Balancers in AWS

Load balancers act as traffic cops for your apps. They send incoming requests to healthy servers, boost uptime, and scale with demand. AWS offers several types under Elastic Load Balancing (ELB), including the Application Load Balancer (ALB) and Network Load Balancer (NLB). Both ensure high availability, but they shine in different spots. For instance, if your setup involves web apps or real-time data, knowing their strengths saves time and money.

Think of load balancers as gateways. They check health, route smartly, and handle failures. Without them, a single server crash could take down your site. ALB and NLB build on this but target specific layers in the OSI model.

What is an Application Load Balancer (ALB)?

An Application Load Balancer works at Layer 7 of the OSI model. This means it looks deep into HTTP and HTTPS requests. It reads headers, paths, and hosts to route traffic wisely. For example, send shopping cart requests to one server group and login pages to another.

Key ALB features include:

• Content-based routing: Route based on URL paths, hostnames, or query strings. Great for microservices where different parts handle specific tasks.
• Path-based routing and host-based routing: Run multiple apps behind one balancer.
• SSL termination: Offload encryption to free up your servers.
• Advanced health checks: Verify app content, not just connections.
• Support for HTTP/2 and gRPC: Speeds up modern web apps.

ALB fits well with containerized apps like those in ECS or Kubernetes. It registers targets dynamically, so scaling feels seamless. If you’re building a web store or API gateway, ALB gives the flexibility you need.

Pros of ALB:

• Smarter routing for complex apps.
• Built-in security like WAF integration.
• Easy integration with AWS services.

Cons:

• Slightly higher latency from deep inspection.
• No static IPs out of the box.

What is a Network Load Balancer (NLB)?

A Network Load Balancer operates at Layer 4, focusing on transport protocols like TCP, UDP, and TLS. It forwards packets fast without peeking into app data. This makes it ideal for high-speed needs.

Standout NLB features include:

• Static IP load balancer AWS: Assign Elastic IPs for predictable addressing.
• TCP/UDP traffic handling: Perfect for non-HTTP workloads like databases or streaming.
• Ultra-low latency: Handles millions of requests per second.
• Source IP preservation: Clients see original IPs, useful for logging.
• Zonal isolation: Traffic stays in one Availability Zone if needed.

NLB excels in scenarios like gaming servers or IoT devices where speed trumps smarts. It also supports PrivateLink for secure VPC connections.

Pros of NLB:

• High performance load balancing for volatile traffic.
• Lower costs for high throughput.
• Simple setup for basic routing.

Cons:

• No app-layer awareness, so less flexible routing.
• Basic health checks via ping or handshake.

Key Difference Between Application Load Balancer and Network Load Balancer

Now, let’s pinpoint the difference between application load balancer and network load balancer. These tools differ in layers, speed, and smarts, affecting your architecture choices.

OSI Model Layers in Load Balancing

ALB sits at the application layer traffic routing (Layer 7), examining request details. NLB works at the transport layer load balancing (Layer 4), dealing with connections only. This core split means ALB understands content, while NLB prioritizes speed.

Protocols and Traffic Types

ALB handles HTTP, HTTPS, and gRPC – think web traffic. NLB supports TCP, UDP, and TLS, covering broader needs like video streams or custom protocols. For HTTP vs TCP load balancing, choose ALB for web, NLB for everything else.

Routing Capabilities

ALB offers ALB routing rules like path or host-based. NLB routes via IP and ports, keeping it simple. If you need content-based routing AWS, go with ALB.

Performance and Latency

Is Network Load Balancer faster than Application Load Balancer? Yes, often. NLB’s NLB performance shines with low latency and high throughput – up to millions of RPS. ALB adds overhead from inspection but still scales well for most app¹s.

Health Checks

Health checks Layer 4 vs Layer 7: NLB uses basic TCP or ping checks. ALB verifies HTTP status codes and content, catching app issues faster.

Target Types and Integrations

Both support EC2 instances and IPs. ALB adds Lambda; NLB can target ALBs for hybrid setups. For ALB vs NLB for Kubernetes Ingress, NLB suits LoadBalancer services, ALB for Ingress.

Cost Difference Between Application and Network Load Balancer

Pricing uses hours and LCUs. ALB costs $0.0225 per hour + $0.008 per LCU-hour. NLB is $0.0225 per hour + $0.006 per LCU-hour. LCUs measure connections, bytes, and rules. NLB often runs cheaper for high-volume TCP traffic, but calculate based on your load.

For a mid-sized app with 20 RPS to Lambda, ALB might cost around $32 monthly. Always check AWS calculator for exacts.

Security and Availability

Both offer high availability and fault tolerance. ALB integrates with WAF for threats. NLB preserves IPs for better auditing. Use security groups on both.

Here’s a quick comparison table:

This table highlights core diffs for quick scans.

To visualize, check these diagrams:

medium.com

When Should I Use an ALB Instead of an NLB?

Ask: How to choose between ALB and NLB for my application? If your traffic is HTTP-based with need for protocol-level routing, pick ALB. For ALB vs NLB for HTTP and TCP traffic, use ALB for web, NLB for mixed or non-HTTP².

When to use content-based routing with ALB: In microservices, route /api/users to user service, /api/orders to order service³.

ALB vs NLB use cases for real-time applications: NLB for gaming or VoIP due to low latency network traffic.

Best load balancer for microservices on AWS: ALB, with its dynamic scaling.

Can NLB handle HTTPS traffic? Yes, via TLS, but without Layer 7 smarts.

For mixed workloads, layer them: NLB fronting ALB.

Examples:

• E-commerce site: ALB routes to cart, product pages.
• Streaming service: NLB handles UDP video feeds.
• API backend: ALB for RESTful services.

Stats show AWS ELB handles billions of requests daily, with NLB cutting latency by up to 50% in high-load tests.

Tips for Implementing Load Balancers

1. Assess traffic: Web? Use ALB. TCP/UDP? NLB.
2. Test health checks: Tune for your app.
3. Monitor metrics: Use CloudWatch for throughput.
4. Scale smart: Enable cross-zone for even load.
5. Secure: Add SSL and groups.

For throughput and latency optimization, NLB wins for bursts. ALB for cloud infrastructure scaling in containers.

Migrating? AWS wizard helps from Classic to ALB/NLB.

Common Challenges and Solutions

New to AWS? Start with ALB for web basics. For performance comparison between ALB and NLB, NLB edges out in speed but lacks routing depth.

Does ALB support static IPs? No, but pair with NLB.

For containerized app load balancing, ALB’s dynamic ports help.

Which AWS load balancer is best for high throughput workloads? NLB.

Avoid pitfalls: Don’t use ALB for UDP – it won’t work.

FAQs

What is the difference between AWS Application Load Balancer and Network Load Balancer? 

ALB is Layer 7 for HTTP routing; NLB is Layer 4 for fast TCP/UDP.

When should I use an ALB instead of an NLB? 

For content routing in web apps.

ALB vs NLB for HTTP and TCP traffic? 

ALB for HTTP, NLB for TCP.

Is Network Load Balancer faster than Application Load Balancer? 

Yes, due to less processing.

How to choose between ALB and NLB for my application? 

Based on protocols and routing needs.

Conclusion 

In conclusion, grasping the difference between application load balancer and network load balancer empowers you to build resilient systems. ALB offers smart routing for web-focused apps, while NLB delivers raw speed for diverse traffic. Choose based on your workload – web for ALB, high-performance for NLB – to optimize costs and performance. With AWS’s tools, scaling becomes straightforward.

Which load balancer will you try first for your next project?

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References

1. Application load balancer vs network load balancer – Community insights for beginners. ↩︎
2. Application vs. network load balancing: What’s the difference? – General concepts on load balancing types. ↩︎
3. AWS — Difference between Application load balancer (ALB) and Network load balancer (NLB) – Detailed feature breakdown. ↩︎