Azure Load Balancing Solutions:

Understanding about Load Balancer, Application Gateway, Traffic Manager, and CDN

Introduction

In this cloud-driven world, we need to ensure high availability, scalability, and performance for our every application. Microsoft Azure provide different types of Load-balancing and Regional and Global traffic distribution solutions to users and each of these services designed for specific requirements. Before jumping to the Load-balancing Services first we need to understand OSI architecture.

OSI Architecture

The OSI (Open Systems Interconnection) Model is a conceptual framework that standardizes and divides the all-network communication into seven layers. Each of the layers has specific own job functions and interacts with each other above and below it.

OSI Model 7 Layers

Physical Layer –This Layer mainly Deals with hardware, cables, signals, and data transmission (e.g., Ethernet, Fiber Optics).

Data Link Layer – This Layer is Ensures error-free transfer between nodes and working with mainly Switches and NIC’s (e.g., MAC addresses, switches).

Network Layer – This Layers is primarily Handles routing and addressing based on Routers and Layer 3 Switches (e.g., IP, routers).

Transport Layer – Ensures reliable data transfer (e.g., TCP, UDP).

Session Layer – Manages sessions between applications. And this layer is responsible for the continues session running. (e.g., authentication, API sessions).

Presentation Layer – All our Translates, encrypts, and compresses data is handling in this Layer. (e.g., SSL, JPEG, ASCII).

Application Layer – ThisInterfaces is mainly interacted with user and applications (e.g., HTTP, FTP, SMTP).

Now we can see azure provided Load balancing Services

This guide explores four key Azure services:

• Azure Load Balancer (Working on OSI-Layer 4)
• Azure Application Gateway (Working on OSI-Layer 7)
• Azure Traffic Manager (DNS-based global load balancing)
• Azure Content Delivery Network (CDN) (Global Edge caching for fast content delivery)

End of this article you can understand each of their differences and use cases, you can optimize your Azure infrastructure for reliability and speed.

1. Azure Load Balancer (Layer 4 – Transport Layer)

What is Azure Load Balancer?

Azure Load Balancer operates at Layer 4 (Transport Layer – TCP/UDP) and distributes incoming traffic across multiple virtual machines (VMs) or instances to ensure high availability.

Key Features:

• High Availability: Distributes traffic across healthy VMs.
• Internal & Public Load Balancing:
  • Public Load Balancer: Routes internet traffic to VMs in the same VNet’s.
  • Internal Load Balancer: Balances traffic within a virtual network (VNet).
• Port Forwarding: Directs traffic to specific ports.
• Health Probes: Monitors backend instances and removes unhealthy ones.

Use Cases:

• Load balancing for non-HTTP(S) traffic (e.g., databases, gaming servers).
• High availability for VM scale sets (usually we place Load balancer upfront of the Scale Sets. Traffic first hit on the Load balancer and then load balancer route the traffic to backend Scale sets).
• Port-based routing for multi-tier applications.

2. Azure Application Gateway (Layer 7 – OSI Application Layer)

What is Azure Application Gateway?

Azure Application Gateway is a Layer 7 (HTTP/HTTPS) load balancer that provides advanced traffic routing, SSL termination, and web application firewall (WAF) capabilities for our Cloud infrastructures and outside infrastructures.

I have separate demo for the application Gateway.

Key Features:

• URL Path-Based Routing: Directs traffic based on URL paths (ex: /videos /images).
• SSL/TLS Termination: Offloads encryption/decryption to improve loading performance.
• Web Application Firewall (WAF): Protects against common web exploits (SQL injection, XSS and OWASP Top 10 threats).
• Session Affinity: This feature is ensures user sessions stay on the same backend server.
• Autoscaling: Handles traffic spikes dynamically.

Use Cases:

• Web applications require path-based routing.
• E-commerce web sites need WAF protection.
• API gateways with SSL offloading.

3. Azure Traffic Manager (DNS-Based Global Load Balancing)

What is Azure Traffic Manager?

Azure Traffic Manager is a Microsoft Azure provides DNS-based global traffic distributor that routes users to the closest or best-performing azure and non-azure endpoint  across regions .

Key Features:

• Multiple Routing Methods:

Azure traffic manager provide different type of routing methods and we can use that methods based on our requirements.

• Performance base: Routes users to the lowest-latency endpoint
• Geographic base: Directs traffic based on user location (Closet Endpoints).
• Priority base: Fails over to backup endpoints if primary fails. We can pre configure the numbers.
• Global High Availability: Works across Azure and non-Azure endpoints.
• Health Checks: Automatically reroutes traffic if an endpoint fails.

Use Cases:

• Multi-region deployments for disaster recovery.
• Global SaaS applications needing low latency.
• Hybrid cloud setups balancing on-prem and cloud workloads.

4. Azure Content Delivery Network (CDN) – Fast Content Delivery

What is Azure CDN?

Azure CDN caches static and dynamic content at edge locations worldwide, reducing latency and improving load times of websites.

Key Features:

• Global Edge Network: 200+ POPs (Points of Presence) for fast content delivery.
• Static & Dynamic Content Acceleration: Caches images, videos, APIs.
• DDoS Protection: Integrated with Azure DDoS Protection.
• Custom Domains & HTTPS: Secure and branded content delivery.

Use Cases:

• Media streaming (videos, live events).
• Global websites with heavy static content.

Comparison Table: Which One Should You Use?

Conclusion: Now you can Choosing the Right Azure Load Balancing Solution for the your requirements.

• If need basic TCP/UDP load balancing? → You can go with Azure Load Balancer
• If need running web apps with advanced routing/WAF? → You can go with Application Gateway
• If need global traffic distribution? → You can use Azure Traffic Manager
• Need delivering content worldwide fast. → Azure CDN is resolve that

By combining these services, you can build a highly available, scalable, and performant cloud architecture in Azure.

Would you like a deeper dive into any of these services? Let me know in the comments!

I will add demo articles for the Azure Traffic Manager and CDN Service soon. Stay tuned.