What is a Load balancer in Azure?

The most important component of cloud computing is the optimal management of resources to warrant the system's proper running. A very important element of this context is the load balancer. Now, it’s time to explain what an Azure Load Balancer is, how it works, and why it is critical for your cloud environment.

This report focuses on the basics of load balancing.

Before I proceed to giving you an insight into Azure, let me give brief information about load balancing. Suppose you have a trendy restaurant—yes, suppose you are the owner of a restaurant that people flock to. More customers mean that you have to spread them across tables and servers to accord all clients quick service. In the same manner, a load balancer also handles a similar function in the aspect of the flow of network traffic.

On a more specific level, a load balancer receives incoming network traffic in a network and spreads it out among the available servers so that none of the servers gets overloaded. This enhances the interactivity with applications, databases, or websites.

 Key Features of Azure Load Balancer:

 1. High Availability: Improves application resilience by distributing traffic across multiple healthy instances.

 2. Scalability: Can handle millions of requests per second, allowing your applications to scale as needed.

 3. Internal and External Traffic Management: Can balance traffic within a virtual network or from the internet to your Azure resources.

 4. Health Probes: Monitors the health of your application instances and only sends traffic to healthy instances.

 5. Port Forwarding: This allows you to map public ports to internal ports for specific VMs.

 6. Outbound Connections: Provides outbound connectivity for VMs inside your virtual network.

Types of Azure Load Balancers

Azure services offers two main types of load balancers:

 1. Public Load Balancer

   - Provides outbound connections for VMs inside your virtual network

  - Translates private server IP addresses to public server IP addresses

   - Load balances internet traffic to your VMs

2. Internal Load Balancer

   - Used when you need private front-end IP addresses only

   - Used to load balance traffic inside a virtual network

   - Ideal for multi-tier applications where back-end tiers shouldn't be exposed to the internet

How Azure Load Balancer Works

When a client sends a request to your application, here's what happens:

1. The request hits the load balancer's front-end IP configuration.

2. There are rules enforced on the load balancer as to which back-end pool should serve the traffic.

3. It then uses a hashing algorithm to select a specific instance in the back-end pool based on the source IP, destination IP, source port, destination port, and protocol type.

4. The selected instance performs the request and sends it back to the client through the load balancer.

Load Balancing Rules

 Load balancing rules define how traffic is distributed. They consist of:

- A front-end IP configuration

- A back-end address pool

- A health probe

- Load balancing algorithm (default is a 5-tuple hash)

Health Probes

Health probes are crucial for maintaining high availability. They regularly check the health of instances in your back-end pool. If an instance fails to respond to a health probe, it's automatically removed from rotation until it becomes healthy again.

Load Balancing Algorithms

Azure Load Balancer uses a hash-based algorithm by default. It creates a hash based on:

- Source IP

- Destination IP

- Source port

- Destination port

- Protocol type

This hash determines which back-end instance will receive the traffic. This ensures that requests from a specific client always go to the same back-end instance for the duration of a session.

SKUs: Basic vs. Standard

Azure Load Balancer comes in two SKUs (Stock Keeping Units):

1. Basic

   - Free, included with virtual machines

   - Supports up to 300 instances in the back-end pool

   - Limited to a single availability set or virtual machine scale set

2. Standard

   - Paid service with more features

   - Supports up to 1000 instances in the back-end pool

   - Can span multiple availability sets, virtual machine scale sets, or stand-alone VMs

   - Provides better availability and additional features like zone redundancy

When to Use Azure Load Balancer

You should consider using Azure Load Balancer when:

1. You have to spread the traffic through many instances of your application.

2. You require increasing the large degree of availability and anti-frailness of the offered services.

3. You are running applications that require the allocation of resources relative to the level of traffic.

4. You must configure the virtual network to set up several specific settings, but the most critical one of them is outbound connectivity for the VMs in this virtual network.

Azure Load Balancing vs. Cloud Load Balancing

Azure Load Balancing is a service offered by Microsoft Azure that distributes incoming traffic across multiple virtual machines (VMs) or services within the Azure ecosystem. It supports both Layer 4 (TCP/UDP) and Layer 7 (HTTP/HTTPS) load balancing, offering options like Azure Load Balancer, Application Gateway, and Traffic Manager. Azure Load Balancer is ideal for managing internal and external traffic, providing high availability, scalability, and fault tolerance.

Cloud Load Balancing is a more generic term that refers to load balancing across various cloud platforms, such as AWS, Google Cloud, or other cloud providers. Each platform has its own load balancing services, such as AWS Elastic Load Balancing (ELB) or Google Cloud Load Balancing, with features that may include global distribution, content-based routing, and auto-scaling. Cloud load balancing generally offers similar functionality to Azure's services but varies depending on the specific provider’s capabilities and integrations within their ecosystem.

In essence, Azure Load Balancing is a specialized service within the Azure platform, while cloud load balancing can refer to similar services across different cloud providers. The choice between them depends on your existing cloud environment, specific requirements, and preferred platform.

Conclusion

You will recall that Load Balancer is one of the foundation elements of your cloud resources portfolio. It helps in ensuring that your applications remain effective, efficient, and adaptive. It also equally assists in distributing traffic across resources that host your services on Azure; it is thus very useful in aspects of performance and availability.

However, like any cloud hosting service, it is crucial to comprehend what it can do and where it best suits the given structure. In the correct deployment, Azure Load Balancer can greatly improve the availability and reliability of your cloud applications hosting.