What Are Load Balancing Algorithms? All You Need To Know

Picture a restaurant host seating incoming guests in different parts of the restaurant to distribute the workload among the waitstaff. The host aims to ensure that no single server feels overwhelmed or becomes responsible for more tables than they can handle. This process also means guests receive timely service.

In cloud services, load balancing algorithms work the same way. Network administrators and IT managers use load balancing software to portion out resources to websites and applications so they get the most from their resources. 

The primary goal is to prevent any single server from becoming overloaded, ensuring optimal performance, high availability, and efficient resource utilization.  

How does load balancing work?

Every day, billions of people access modern applications through the internet. Applications usually run on multiple servers. Load balancing tools facilitate task distribution to prevent any server from getting overwhelmed and slowing down or, worse, crashing. It helps disburse work evenly across multiple servers so users can access applications without delay or interruption. 

To make this happen, developers created load balancers, devices, or software programs responsible for traffic distribution. Network administrators place them between users and servers. When a user attempts to connect to an application, the load balancer reviews the request and chooses the most suitable server. 

The process works behind the screens, invisible to users so they don’t see their requests funneling through load balancers. Instead, they ask for various web pages and receive results while the load balancer works to present the pages they request – almost like magic. 

You can compare load balancing to a traffic conductor’s responsibility (except that a traffic director is visible and load balancers aren’t). Think about a busy intersection that’s under construction with no operating stoplights. Without a traffic controller, cars might not take turns passing through the intersection, which will eventually lead to accidents and traffic jams. 

The traffic director guides vehicles through the intersection at reasonable intervals, balancing the traffic load to make certain everything flows smoothly and to reduce the likelihood of accidents. In this example, the traffic director is the load balancer, the cars are the tasks that users request, and the roads are the servers. 

Benefits of load balancing

Load balancing boosts the efficiency, dependability, and scalability of systems managing heavy traffic, resulting in an enhanced user experience. Load balancing algorithms offers several key benefits:

• Improved performance: By distributing traffic across multiple servers, load balancing minimizes wait times for users, leading to a faster and more responsive experience. Handling several requests concurrently boosts overall system capacity and efficiency, leading to an improved performance.  
• Fault tolerance: If one server fails, load balancing algorithms seamlessly redirect traffic to other available servers, ensuring minimal downtime and uninterrupted service.   
• Scalability: Adding new servers to the pool is straightforward, allowing for easy scaling to accommodate growing traffic demands.   
• Resource optimization: Load balancing prevents resource bottlenecks by distributing the workload evenly, maximizing the use of available resources.   
• Reduced costs: By efficiently utilizing existing hardware, organizations can potentially reduce the need for costly server upgrades.

Types of load balancing algorithms 

Load balancing algorithms fall into one of two types: static or dynamic. Let's learn more about the types of load balancing algorithms. 

Static load balancing algorithms 

Static load balancing algorithms follow fixed rules to distribute traffic evenly across servers. Rather than considering the current state or load of the servers, they rely on predetermined rules. Due to their straightforwardness, static load balancing algorithms are generally easier to implement than dynamic ones. However, they don’t always handle various server loads efficiently. 

Below are some of the standard static load balancing algorithms. 

Round-robin method

In round-robin distribution, load balancers distribute incoming user requests across servers in a rotational order. The load balancer works its way through a list of servers until it reaches the end. Then, the process starts over, and the load balancer starts assigning requests at the top of the list in the same order. Remember that all static algorithms, including the round-robin method, assume all servers are available, regardless of capacity. 

Examples:

• Small business websites: Distributing traffic across a few servers with similar configurations.  
   
• Basic web applications: Where even distribution of requests is sufficient for maintaining performance. 

Weighted round-robin method

A weighted round-robin calls on more advanced methods than a traditional round-robin assignment. Instead of equal distribution, a weighted algorithm allows you to assign weights to each server, typically based on the server’s capacity. The load balancer uses the assigned weights to allocate requests accordingly. 

Servers with higher weights receive a larger proportion of the incoming requests. The distribution is rotational, similar to the traditional round-robin technique, but servers receive requests proportional to their weight throughout the cycle. 

Examples:

• Server farms with servers of different specifications: Distributing traffic based on server capacity, ensuring that more powerful servers handle a larger share of the workload.  
   
• Cloud environments: Distributing traffic across virtual machines with varying resource allocations.

IP hash method

The load balancer uses the IP hash method to generate a hash value from the user’s IP address. It then takes the hash value and assigns the client to a specific server. All requests from that client are associated with their hash, and the load balancer will send the user to the same server with each new request. 

Examples:

• Online banking applications: Maintaining user sessions and ensuring secure transactions.
• E-commerce websites: Preserving shopping cart contents and user preferences.
• Online gaming servers: Maintaining game state and player connections.

Dynamic load balancing algorithms 

Unlike static load balancing algorithms, dynamic load balancing algorithms examine the current state of servers before distributing incoming network traffic. While more complex, these algorithms perform better for efficient resource distribution and server load handling. Below are some typical dynamic load balancing algorithms. 

Least connection method

When clients connect to a server, they establish an active connection in order to communicate. When a load balancer uses the least connection method, it looks at the servers to determine which ones have the fewest active connections and sends incoming traffic to them. This method assumes that the servers with the least connections have the most available capacity.

Examples:

• Web servers handling dynamic content: Where request processing times can vary significantly based on the complexity of the request.
• Applications with long-running connections: Such as database servers or streaming services.

Weighted least connection method

The weighted least connection method is an advanced configuration of least connection algorithms. Like the static version of the weighted round-robin method, you can assign weights to each server with this algorithm. The load balancer will distribute new requests to the server with the least connections by weighted capacity.

Examples:

• Cloud environments with virtual machines of varying sizes: Distributing traffic based on the resources allocated to each VM.
• Server farms with servers of different specifications: Prioritizing more powerful servers while considering the current load on each server.

Least response time method

Response time means the time a server takes to process an incoming request and send a response back to the user. The least response time method evaluates server response times so the load balancer routes incoming requests to the fastest-responding server.

Examples:

• Gaming servers: Where low latency is crucial for a smooth and enjoyable gaming experience.
• Real-time communication applications: Such as video conferencing or online gaming, where delays can significantly impact user experience.
• High-performance computing clusters: Where minimizing job completion times is critical.

Resource-based method

In the resource-based method, load balancers distribute traffic by analyzing current servers. The load balancers look for a server with sufficient resources before sending any data.

Examples:

• Database servers: Distributing database connections based on server load and available resources.
• High-performance computing clusters: Distributing jobs to nodes with the most available resources.

Top 5 load balancing software programs

Load balancing software distributes resources and incoming traffic to applications and websites in order to help network administrators and IT managers control resources efficiently. 

To qualify for inclusion in G2’s load balancing category, a product must:

• Monitor web traffic and distribute resources
• Scale infrastructure workloads to match traffic
• Provide, or integrate with, failover and backup services

Below are the top five leading load balancing platforms from G2’s Summer 2024 Grid® Report. Some reviews may be edited for clarity. 

1. HAProxy

HAProxy powers modern application delivery at scale in any environment. It offers comprehensive load balancing methods, including round robin, least connections, and several hashing techniques. Users can turn on advanced routing decisions based on URL, domain name, file extension, IP address, or active connections. 

What users like best:

“We migrated from Snapt load balancer (software based) to HAProxy Enterprise (software based). This also came with the HAProxy Fusion. HAProxy has been performant and stable across the multiple clients we service and allows configuration changes that do not impact our clients. This has been a huge step up for our stability and confidence in our solution. Since it is software-based, we have easily incorporated the solution into our disaster recovery solution.

The product is very competitively priced, and we have received phenomenal support. I would highly recommend this product.”

- HAProxy Review, Nathan H. 

What users dislike:

“Would love a more in-depth user interface (UI) from the open source version.”

- HAProxy Review, Colin C. 

2. Cloudflare Application Security and Performance

Cloudflare Application Security and Performance’s load-balancing solution guarantees high performance, uptime, and quality user experience by balancing traffic across geographically distributed servers and data centers. With this dynamic platform, users can manage traffic across multiple protocols to tailor the configuration and meet their business needs. 

What users like best:

“Cloudflare's comprehensive features boost your site's speed and shield it from various online threats. 

Cloudflare also provides free secure sockets layer (SSL) certificates for secure data transmission, optimizes images for faster loading, and streamlines files through minification. Browser caching, WebSockets for real-time communication, load balancing, rate limiting, optimized network routing, page rules for customization, and the AMP Real URL feature for maintaining your brand identity in Google AMP results are all part of Cloudflare's robust toolkit for optimizing and securing your website.”

- Cloudflare Application Security and Performance Review, Chandra Shekhar T. 

What users dislike:

“So far, there isn't anything that I dislike. However, they can improve the language in their UI, which is full of jargon for techies. Or they could offer a simple UI view for non-techies and an advanced view for techies.”

- Cloudflare Application Security and Performance Review, Jay K. 

3. F5 NGINX Ingress Controller

F5 NGINX Ingress Controller uses a universal Kubernetes tool for implementing application programming interface (API) gateways and load balancers. It provides app protection at scale through strong security controls and distributed environments, and prevents app downtime through advanced connectivity patterns and troubleshooting processes. 

What users like best:

“It reduced the complexity of Kubernetes application traffic. F5 NGINX Ingress Controller simplifies the management and optimization of traffic flow to your Kubernetes applications and provides advanced networking and security features to ensure their reliability and security.”

- F5 NGINX Ingress Controller Review, Shubham S. 

What users dislike:

“When considering F5, weighing the benefits, such as advanced traffic management and security features, is important against potential downsides, such as cost and complexity. While it is a reliable solution for managing Kubernetes' ingress traffic, users may need to invest time and resources to learn and implement it effectively.”

- F5 NGINX Ingress Controller Review, Bhargav N. 

4. Kemp LoadMaster

Kemp LoadMaster offers load balancers for high-performance balancing and application delivery. It provides hardware, virtual, and cloud-native deployment load balancers to meet varying needs. Kemp LoadMaster solutions also come with an extensive library of application deployment templates. 

What users like best:

“Kemp Loadmaster is a flexible, solid, and reliable system. The customer service support is tremendous, and I recommend getting good support maintenance.”

- Kemp LoadMaster Review, Anthony C. 

What users dislike:

“Kemp LoadMaster is a bit higher priced than other load-balancing solutions in the market.” 

- Kemp LoadMaster Review, Tony W. 

5. F5 NGINX Plus

F5 NGINX Plus is an all-in-one API gateway, content cache, load balancer, and web server with enterprise-grade features. The NGINX Plus load balancer is high-performance and lightweight for various network and development operations needs.

What users like best:

“F5 NGINX Plus is one of the best API monitoring and security enhancing platforms that simplifies modernizing legacy applications, and delivering micro-services applications to enterprises undergoing digital transformation.”

- F5 NGINX Plus Review, Manya V. 

What users dislike:

“The current Trial is for 30 days for NGINX Plus and should have been at least 90 days for the platform to understand how the return on investment would be if it is purchased.”

- F5 NGINX Plus Review, Mohammad S. 

Load balancing: Frequently asked questions (FAQs)

What is the random algorithm for load balancing?

The "random" algorithm distributes incoming requests randomly across available servers. It's a simple approach that can be effective in some situations, but it doesn't consider server load or other factors.

Which algorithm is best for imbalanced data?

For imbalanced data, algorithms that consider server load or performance are generally preferred. Least connections and Least response time can be good choices, as they dynamically adapt to changing server conditions.

What is session affinity and why is it important?

Session Affinity ensures that requests from the same user are always directed to the same server. Important for applications that rely on session data (e.g., online shopping carts, user logins).  

How do load balancers handle server failures?

Load balancers handle server failures by regular health checks, automatic removal of unhealthy servers, and failover.

Which algorithm is best for load balancing? 

There is no "best" algorithm. The optimal choice depends heavily on the specific needs and characteristics of your system. Factors to consider include: traffic patterns, server capabilities, and application requirements.

Off balance?

Load balancing algorithms fundamentally maintain the efficiency and reliability of modern applications and websites. They work hard to make sure no single server gets overloaded so companies can provide smooth and uninterrupted service for users worldwide. Whether you manage a cloud environment or run a bustling e-commerce business, load balancing will enrich the user experience. 

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