Azure Load Balancer vs Application Gateway: Comparison Guide

If you're planning to deploy a scalable and secure application on Azure, you've likely come across two popular options: Azure Load Balancer and Application Gateway. Both are designed to distribute traffic and improve app performance, but they serve different purposes and have distinct features.

Azure Load Balancer is a layer 4 load balancer that provides basic load balancing capabilities, routing traffic to multiple instances of your app. It's a simple and cost-effective solution for small to medium-sized applications.

Application Gateway, on the other hand, is a layer 7 load balancer that offers more advanced features, including SSL termination, URL rewriting, and caching. It's ideal for large-scale applications that require high availability and security.

In this comparison guide, we'll delve into the key differences between Azure Load Balancer and Application Gateway, helping you decide which one is right for your Azure deployment.

Azure Load Balancer is a powerful tool that helps scale applications and create highly available services by distributing incoming requests across multiple backend resources. It's like a traffic cop, directing traffic to the right place to ensure that your application runs smoothly.

One of the key features of Azure Load Balancer is its ability to scale layer 4 load balancing of both internal and external traffic to VMs and VM scale sets. This means that it can handle a large volume of traffic and distribute it across multiple virtual machines.

Azure Load Balancer also provides increased availability through zone redundancy, which ensures that your application remains available even if one of the zones fails. This is achieved through health monitoring and automatic failover with health probes.

Here are some of the key use cases enabled by Azure Load Balancer:

With built-in metrics and logs, Azure Load Balancer provides crucial visibility into the health and performance of load-balanced workloads. This is essential for monitoring and troubleshooting issues that may arise.

Azure Load Balancer Components are the building blocks of a reliable and scalable network. The Frontend IP Configuration is the entry point for clients, and it can be public or private.

A Frontend IP Configuration can be either a Public IP Address or a Private IP Address, which determines whether the load balancer is public or internal. This configuration is crucial in defining how clients interact with the load balancer.

Azure Load Balancer Components include a Backend Pool, which is made up of virtual machines or instances that serve incoming requests. Scaling for increased traffic volume is typically achieved by adding more instances to the backend pool.

A Backend Pool consists of virtual machines or instances in a virtual machine scale set responsible for serving incoming requests. The number of instances in the backend pool can be scaled up or down to handle changing traffic demands.

Health Probes are used to determine the health status of instances within the backend pool. A health probe is configured during load balancer creation to assess whether an instance is healthy and can receive incoming traffic.

Here's a summary of the key Azure Load Balancer Components:

Balancing is a crucial concept in load balancing, and it's essential to understand what it entails.

Azure Load Balancer uses a load balancing algorithm to distribute incoming traffic across multiple instances of a service.

This ensures that no single instance is overwhelmed, and the service remains responsive and available.

The load balancing algorithm used by Azure Load Balancer is a proprietary algorithm, but it's designed to be highly efficient and scalable.

It takes into account factors such as instance availability, network latency, and traffic patterns to make informed decisions about where to send traffic.

Azure Load Balancer can also be configured to use a health probe to monitor the health of instances and direct traffic away from unhealthy instances.

This helps to prevent the service from becoming unresponsive due to a single instance failure.

The Azure Load Balancer is made up of several essential components that work together to distribute traffic and ensure high availability. The Frontend IP Configuration is the point of contact for clients interacting with your Azure Load Balancer, and it can be configured with either a Public IP Address or a Private IP Address.

You can configure the Frontend IP configuration using various tools like the Azure portal, Azure CLI, Azure PowerShell, Resource Manager Templates, or other appropriate alternatives. This is a key consideration when setting up your Azure Load Balancer.

The Backend Pool consists of virtual machines or instances in a virtual machine scale set responsible for serving incoming requests. Scaling for increased traffic volume is typically achieved by adding more instances to the backend pool, ensuring cost-effective operations.

Health Probes play a crucial role in determining the health status of instances within the backend pool. During load balancer creation, a health probe is configured to assess whether an instance is healthy and can effectively receive incoming traffic.

Here are the key components of the Azure Load Balancer:

SSL/TLS termination is supported by both NGINX Plus and Azure Application Gateway. Azure Load Balancer does not support SSL/TLS termination.

If you need to secure incoming traffic, consider using NGINX Plus or Azure Application Gateway, which can handle SSL/TLS termination.

Azure Application Gateway is a centralized access point that efficiently distributes incoming application traffic across various backend pools. It supports public, private, or both frontend IP addresses, and requires the virtual network and public IP address to be in the same location.

A key feature of Application Gateway is its ability to route traffic based on URL path, host headers, and cookies, making it ideal for web applications and APIs. Multiple listeners can be attached to an Application Gateway, supporting various protocols and ports.

Here are the key components of Azure Application Gateway:

Azure Application Gateway is a fully managed service that provides a secure and scalable entry point for your web applications. It helps protect your web applications from common web exploits and provides a high level of security.

Application Gateway can be used as a reverse proxy, load balancer, or web application firewall. It's designed to handle high traffic and provides a high level of availability.

The gateway can be configured to use a custom domain name, making it easier to integrate with your existing infrastructure. This is done by setting up a DNS record that points to the gateway's IP address.

Application Gateway supports multiple protocols, including HTTP and HTTPS, and can be used to distribute traffic across multiple instances of your web application. This helps ensure that your application remains available even if one instance becomes unavailable.

Azure Application Gateway is a powerful tool for managing incoming traffic to your applications. It serves as a centralized access point, efficiently distributing traffic across various backend pools.

Frontend IP addresses are crucial to its operation, and you can configure them as public, private, or both. They must be in the same location as the virtual network and public IP address.

Application Gateway supports multiple listeners, which are logical entities that examine incoming connection requests. Each listener can be configured to accept requests that match a specific protocol, port, hostname, and IP address.

Request routing rules dictate how traffic on a listener is routed. These rules bind listeners, backend server pools, and backend HTTP settings, determining whether to forward traffic to the backend and specifying the target backend server pool.

HTTP settings control how traffic is routed to backend servers, including port numbers and protocols. They determine whether the traffic is encrypted or unencrypted, providing end-to-end TLS if specified.

Backend pools route requests to backend servers that serve the requests. They can include NICs, virtual machine scale sets, public IP addresses, internal IP addresses, FQDN, and multitenant backends like Azure App Service.

Application Gateway monitors the health of resources in its backend pool by default, automatically removing unhealthy instances. It continually monitors unhealthy instances and reintegrates them into the healthy pool once they become available and respond positively to health probes.

Here's a summary of the key components of Azure Application Gateway:

Azure Application Gateway offers robust protocol support, including HTTP/2 and WebSocket connections. This means you can handle modern web traffic with ease.

One notable feature is URL rewriting and request redirect, which allows you to modify request paths and file locations internally without changing the URLs advertised to clients. This is a game-changer for web applications that require complex routing.

Azure Application Gateway also supports advanced health checks, which can detect issues with your backend servers and automatically redirect traffic to healthy servers.

Here's a list of protocols and features supported by Azure Application Gateway:

This protocol support and URL rewriting capability make Azure Application Gateway a versatile choice for web applications and APIs.

Azure Load Balancer and Application Gateway both offer a range of features that make them essential tools for modern network infrastructures.

Azure Load Balancer distributes incoming traffic across multiple virtual machines or instances, ensuring high availability, redundancy, and even distribution. It can also provide outbound connectivity to the internet for backend servers and VMs.

Application Gateway, on the other hand, supports SSL/TLS termination, allowing encryption to be handled at the gateway. It also offers a range of features, including autoscaling, zone redundancy, and a Web Application Firewall (WAF) service.

Here are some key features of both Azure Load Balancer and Application Gateway:

Balancing Methods are a crucial aspect of load balancing, and both Azure Load Balancer and NGINX Plus offer a range of methods to choose from.

Azure Load Balancer offers one load balancing method, Hash, which uses a key based on the SourceIPAddress, SourcePort, DestinationIPAddress, DestinationPort, and Protocol header fields to choose a backend server.

NGINX Plus, on the other hand, offers a choice of several load-balancing methods, including Least Connections, Least Time, IP Hash, Generic Hash, and Random.

The Least Connections method sends each request to the server with the lowest number of active connections, while the Least Time method sends each request to the server with the lowest score, which is calculated from a weighted combination of average latency and lowest number of active connections.

IP Hash sends each request to the server determined by the source IP address of the request, while Generic Hash sends each request to the server determined from a user-defined key.

Random sends each request to a server selected at random, with the option to choose between the Least Connections or Least Time algorithm when the two parameter is included.

Here's a summary of the load balancing methods offered by NGINX Plus:

Azure Load Balancer's Hash method is a simple yet effective way to distribute traffic across backend servers, while NGINX Plus offers a range of more advanced methods to suit different use cases.

Azure Load Balancer offers a range of features that make it an essential tool for scaling applications and creating highly available services. One of its key features is the ability to distribute incoming traffic across multiple virtual machines or instances, ensuring high availability and redundancy.

Azure Load Balancer supports both internal and external traffic, and can be configured to handle both TCP and UDP flows. It also provides low latency and high throughput routing, making it ideal for applications that require fast and reliable performance.

The load balancer can be configured to use zone redundancy, which ensures that traffic is distributed across multiple availability zones. This provides an added layer of redundancy and helps to prevent a single point of failure.

Azure Load Balancer also provides outbound connectivity and SNAT support, which allows virtual machines without public IP addresses to communicate with the internet. This is achieved through source network address translation (SNAT), which translates the virtual machine's private IP address into the load balancer's public IP address.

The load balancer uses health probes to determine the health status of instances within the backend pool. During load balancer creation, a health probe is configured to assess whether an instance is healthy and can effectively receive incoming traffic.

Here are some of the key features of Azure Load Balancer:

These features make Azure Load Balancer a powerful tool for scaling applications and creating highly available services. By distributing incoming traffic across multiple virtual machines or instances, the load balancer ensures high availability and redundancy, and provides low latency and high throughput routing.

Rate Limits are a crucial feature for any application, and NGINX Plus offers robust control over traffic to and from your instance. You can configure multiple limits to control the traffic, including limiting inbound connections and the rate of inbound requests.

With NGINX Plus, you can also limit the connections to backend nodes and the rate of data transmission from NGINX Plus to clients. This level of control is essential for managing traffic and preventing overload.

Azure Application Gateway and Azure Load Balancer do not support rate or connection limits, so you'll need to explore other options for rate limiting. Fortunately, you can use other Azure services to configure and enable rate limiting.

NGINX Plus offers a high level of customization and control over traffic limits, making it an attractive option for applications that require strict traffic management.

DNS-Based Traffic Distribution is a powerful feature of Azure Traffic Manager that directs user traffic to the most optimal endpoint. This is done through a global DNS-based traffic load balancer that enhances the availability and performance of applications.

User traffic can be distributed across multiple global endpoints to enhance application responsiveness and fault tolerance. This is achieved through global load balancing.

Traffic Manager supports various routing methods globally, including performance-based routing, which optimizes application responsiveness by directing traffic to the endpoint with the lowest latency. Geographic traffic routing is also supported, based on the geographic location of end-users.

Traffic Manager regularly checks the health of endpoints using configurable health probes, ensuring traffic is directed only to operational and healthy endpoints. This is done through endpoint monitoring.

You can have planned maintenance done on your applications without downtime, as Traffic Manager can direct traffic to alternative endpoints while the maintenance is in progress. This is achieved through service maintenance.

Custom routing policies can be defined based on IP address ranges, providing flexibility in directing traffic according to specific network configurations. This is done through subnet traffic routing.

Here are the different types of traffic routing methods supported by Traffic Manager: