What is Azure Load Balancer?

Azure Load Balancer is a Layer 4 (TCP, UDP) load balancer that distributes incoming network traffic across multiple servers to ensure no single server is overwhelmed with too much traffic. It is a key component of Microsoft Azure's networking services and is designed to provide high availability and reliability for applications.

Key features and characteristics of Azure Load Balancer include:

1. Distribution of Incoming Traffic:

   • Azure Load Balancer distributes incoming network traffic across multiple servers (virtual machines or instances) in a backend pool. This helps in achieving load balancing and ensures that no single server is overwhelmed, thereby improving the performance and availability of applications.

2. Support for Multiple Protocols:

   • Azure Load Balancer supports load balancing for both TCP and UDP protocols. This makes it suitable for a wide range of applications, including web applications, databases, and other services.

3. Public and Private Load Balancers:

   • Azure Load Balancer can be configured as either a public or private load balancer. Public load balancers are assigned a public IP address, allowing them to distribute traffic from the internet to the backend pool. Private load balancers, on the other hand, are used for internal communication within a virtual network.

4. Backend Pool:

   • The backend pool consists of the set of virtual machines or instances that will receive the incoming traffic. Azure Load Balancer continuously monitors the health of these instances and directs traffic only to healthy instances.

5. Health Probes:

   • Azure Load Balancer uses health probes to check the health of instances in the backend pool. If an instance is found to be unhealthy based on the defined health probes, traffic is redirected to healthy instances.

6. Session Persistence:

   • Session persistence can be configured to ensure that a client's requests are consistently directed to the same backend server. This is important for applications that require stateful communication.

7. Load Balancing Rules:

   • Load balancing rules define how incoming traffic should be distributed. They specify the frontend IP configuration, port, and protocol, as well as the backend IP pool, port, and protocol.

8. Azure Resource Manager (ARM) Integration:

   • Azure Load Balancer is fully integrated with Azure Resource Manager, allowing users to define and manage load balancer resources using Azure Resource Manager templates.

9. Cross-Availability Zone Load Balancing:

   • Azure Load Balancer supports distributing traffic across virtual machines deployed in different availability zones. This enhances the availability and resilience of applications.

10. Security Groups and Network Security Groups:

    • Azure Load Balancer integrates with Azure Security Groups and Network Security Groups, allowing users to control network traffic to and from the load balancer.

Azure Load Balancer is commonly used in scenarios where high availability, scalability, and reliability are essential for applications. It is a critical component for ensuring that applications can handle varying levels of traffic and maintain consistent performance.