What is load balancing?

Posted on by Mohammed Noufal | Updated:
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Load balancing is a vital technique in computer networking that involves distributing incoming network traffic or requests across multiple servers or resources. Its primary purpose is to prevent any single server from being overwhelmed by a surge in traffic, thus optimizing performance and ensuring high availability. 

By efficiently distributing the workload, load balancing enhances resource utilization, improves response times, and contributes to a seamless user experience in various online services and applications.

This article will describe load balancing, how it works, the benefits it provides, and some user examples.

Table of contents

Why load balancing is important

In computers and networking, load balancing splits incoming requests or traffic among several servers or resources. This is done to guarantee maximum performance, high availability, and effective use of available resources. Keeping any one server from overloading is the primary goal of load balancing, which enhances the overall performance and stability of the system. 

Load balancing distributes traffic across multiple servers, preventing overload and maintaining consistent performance. It optimizes resource utilization, enhances reliability, and reduces response times. 

Load balancers improve application performance by directing requests to servers with minimal load, reducing response times, and improving user experience. It allows for more servers, prevents single-point failure, and ensures optimal server utilization, leading to cost savings.

How load balancers work

Load balancers successfully distribute incoming network traffic across servers, delivering optimal performance, reliability, and high availability. They act as intermediates between clients (e.g., web browsers) and a collection of servers, efficiently regulating traffic flow depending on various algorithms and criteria. 

When a client accesses a website or an application, this sends a request to the load balancer. The load balancer analyzes the request and decides which server from the pool should handle it. This decision is based on predefined algorithms, including round robin, least connections, and IP hash. The decision can also be based on factors like server health, response time, or geographic proximity. The selected server processes the client's request, generates a response, and sends it back to the load balancer. The load balancer then forwards the response to the client.

Load balancers are constantly monitoring the health and performance of the pool's servers. If one server experiences an outage or malfunction, the load balance will redistribute traffic to the other servers.

Adaptability and scaling

Load balancers are designed to be adaptable and scalable. Load balancers update their routing decisions when traffic changes or new servers are added or deleted to ensure optimal performance and effective resource utilization.

As previously stated, various algorithms and methods are used to achieve this distribution based on server load, response times, and availability. Different hosting dedications (shared, dedicated, etc.) can also influence load-balancing approaches. These choices are mainly divided into two main categories: algorithms and methods and hosting dedication. 

Algorithms and methods

Load balancing uses an algorithm to determine how site traffic is divided among servers. The algorithms and methods listed below constitute the most common approaches to load balancing.

The Round Robin Method

The round-robin method is the simplest of the balancing techniques. Traffic can be distributed evenly by simply passing requests to each server in the infrastructure one by one. When the algorithm has finished traversing the list of instances/servers, it returns to the top and starts over. For example, a request is made in a three-server system, and the load balancer routes it to servers A, B, C, A again, and so on. The round-robin technique works best when all of the server hardware in the infrastructure has comparable computational power and capacity.

The Least Connections Method

By default, the least connections approach load balancing technique routes incoming requests to the server with the fewest active connections. This is the standard load-balancing approach, and it usually provides the best performance. The least number of connections approach is best suited for when server engagement time (the length of time a connection remains active) varies. One server may become overloaded in a round-robin technique. For example, if server A has more active connections than server B, server A may experience pressure. This is not possible with the least connections method.

Weighted Least Connections

The weighted least connections algorithm, also available with the round-robin method, allows each server to be allocated a priority status. For example, if one server has more capacity than another, you might give more weight to the larger server. This implies that in the case of a tie (or another active connection metric), the algorithm would allocate an incoming request to the more heavily weighted server, assuring a less load on the server with less capacity.

Source IP Hash

Each request from a distinct IP is given a key when a load balancer employs a source IP hash, which is then assigned to a server. In addition to distributing traffic throughout the infrastructure equally, this also maintains server consistency in the event of a disconnect and reconnect. A uniquely given IP address will always connect to the same server. Citrix claims that by reducing request and response latency and increasing CPU utilization, caching is widely used on application servers and websites with heavy traffic. 

URL Hash

The URL Hash method uses a hash function to assign clients' requests to specific servers. This is based on the request's unique identifier, often derived from the URL. This method helps ensure that requests with the same identifier (e.g., URL) are consistently routed to the same server, enabling session persistence or maintaining state for the client. Similar to the source IP hash approach, the URL hash method allocates keys based on the requested IP rather than the incoming IP.  

The Least Response Time Method

The least response time approach, which reduces load by combining two layers of balancing, assigns requests based on the number of connections on the server and the shortest average response time. This method is similar to the least connections method and aims to enhance applications' overall performance and responsiveness by directing requests to the server that can respond quickly. 

The Bandwidth and Packets Method

The Bandwidth and Packets Method distributes network traffic across multiple servers based on the amount of bandwidth or the number of packets processed by each server. This method helps optimize network performance, improve resource utilization, and ensure even network traffic distribution. According to which server handles the least amount of traffic (bandwidth), the load balancer assigns requests in the bandwidth and packets method of virtual server balancing.

Custom Load

The custom load method, a complicated algorithm that requires the deployment of a load monitor, uses an array of server metrics (including CPU use, memory, and response time) to decide request assignments. The custom load balancing method involves creating a specialized approach for distributing incoming network traffic across servers based on specific criteria tailored to the needs and requirements of an application or system. Custom load balancing methods are designed to optimize performance, enhance efficiency, and address unique use cases. 

Least Pending Requests (LPR)

The Least Pending Requests (LPR) load balancing method is a technique that aims to distribute incoming network traffic across multiple servers based on the number of pending or queued requests each server is currently handling. HTTP/S requests are monitored and sent to the most available server using the approach of the least pending request. The LPR method ensures even distribution throughout the infrastructure by monitoring each server's availability and simultaneously handling spikes in requests. The goal is to direct new requests to the server with the fewest pending requests. This promotes efficient resource utilization and minimizes response times.

how a load balancer works

Hosting dedication: What we offer at Liquid Web

We provide shared and dedicated load balancers at Liquid Web. Both of these options are entirely manageable. Our network engineers will assist you with everything from design to implementation, administration, and monitoring.

Shared load balancers

Our managed shared load balancers are cost-effective, high-performing, and easily scalable (new web servers can be added to the existing pool of load-balanced servers). You will have complete redundancy with automated failover built in. A shared solution is suitable for sites that have exceeded the capabilities of a single web server.

Managed shared load balancers are affordable plans with 1 Gbps throughput, 100,000 concurrent connections, 2-10 servers, and 1-10 virtual IP addresses.

Managed dedicated load balancers

Our dedicated load balancers are devoted entirely to your organization at Liquid Web. In addition to offering powerful traffic scripting capabilities, an advanced API, high-performance SSL, and a complete set of resources dedicated to your infrastructure around the clock, a dedicated solution offers all the advantages of shared load balancing. Dedicated hardware ensures excellent performance, low latency, and no bottlenecking.

Managed dedicated load balancers are robust infrastructures with capacities of up to 10Gbps, 100,000 (beginning at) concurrent connections, and an unlimited number of servers and IP addresses.

Cloud load balancers

A balancing solution inside the same environment is required as more and more companies operate within (at least partially) cloud environments, as recommended by best practices. Cloud load balancers, similar to their physical counterparts, distribute site traffic among redundant virtual nodes to ensure uptime and reduce performance issues caused by high traffic. The convenience and cost-effectiveness of scaling up to meet demand is an obvious benefit of Cloud Load Balancers over physical equipment. In short, expanding within a cloud environment is less expensive and faster. We at Liquid Web have you covered regardless of the surroundings.  


We at Liquid Web provide several algorithms, including the round-robin method, the least connect method, and the least response time approach.

What is the main purpose of load balancing?

The fundamental goal of load balancing is to optimally balance incoming network traffic among different servers, devices, or resources to optimize performance, increase dependability, and ensure high availability within a system or network. This process is essential for maintaining an efficient and responsive system that can handle varying traffic levels and workload. Here are the main purposes of load balancing: 

  • Optimal resource utilization — Load balancing ensures that each server or resource in a server pool is utilized optimally, preventing any server from overloading while others are underutilized. This maximizes the use of available resources, reducing wastage and improving efficiency.
  • Enhanced performance — Load balancing optimally distributes traffic across multiple servers, preventing any single server from becoming overwhelmed. Users will experience the application more smoothly due to quicker reaction times and enhanced performance. 
  • Scalability — Load balancing enables easy scaling of resources by distributing traffic across a pool of servers. Additional servers can be added to the server pool as traffic increases, allowing the system to handle higher loads and accommodate growth. 
  • High availability and reliability — Load balancers constantly monitor the health and status of servers. If a server becomes unavailable or fails, traffic is automatically redirected to healthy servers, ensuring continuous availability and reliability of services. 
  • Prevention of server overload — By distributing traffic effectively, load balancing prevents any single server from being overwhelmed with requests. This helps maintain stable performance and prevents server crashes due to excessive load.

Benefits of load balancing

The following are some of the most significant benefits of load balancing: 

  • Improved security and DDoS mitigation — Load balancers can incorporate security features like DDoS protection, SSL termination, and web application firewalls (WAFs). Load balancers can shield against DDoS attacks by distributing traffic and filtering malicious requests. They act as an additional layer of security, protecting the system from various cyber threats.
  • Traffic management — Load balancers provide traffic management capabilities, allowing administrators to route specific types of traffic to designated servers based on defined rules or criteria. This aids in better resource management and optimization.
  • Cost-effectiveness — Load balancing solutions, especially software-based ones, are cost-effective as they allow optimal use of existing hardware resources. They eliminate the need for significant hardware investments, making them an economical choice for improving system performance.
  • Flexibility and agility — Load balancers can adapt to changing traffic patterns. They can be easily configured to adjust traffic distribution based on real-time conditions, ensuring agility and responsiveness to varying demands. 
  • Better user experience — By distributing traffic efficiently and ensuring optimal performance, load balancing results in a superior user experience. Users experience faster load times, smooth transactions, and uninterrupted service access.
  • Traffic management — Load balancers provide traffic management capabilities, allowing administrators to route specific types of traffic to designated servers based on defined rules or criteria. This aids in better resource management and optimization. 
  • Fault tolerance — Load balancers offer fault tolerance by rerouting traffic in case of server failures. This helps maintain service continuity and prevents disruptions caused by server outages or failures. 
  • Reduction of overhead — Load balancing reduces the administrative overhead associated with manually managing traffic distribution. Automated distribution of traffic improves operational efficiency and reduces the need for constant manual intervention. 
  • Global availability and redundancy — Load balancing across geographically dispersed servers or data centers ensures global availability of services. Redundancy across different locations further enhances system resilience and disaster recovery capabilities.

Disadvantages of load balancing

The following are some of the disadvantages of load balancing:

  • Cost — Implementing and managing load-balancing solutions can be expensive, especially for smaller organizations.
  • Complexity — Configuring and maintaining Load Balancers can be complex, requiring expertise and time.
  • Potential single point of failure — While load balancers aim to enhance availability, they can become a single point of failure if not designed and implemented correctly.
  • Security — Load balancing can lead to security issues if not implemented correctly, such as permitting unauthorized access or exposing sensitive data.

Hardware vs software load balancing

Hardware and software load balancing are two approaches to divide incoming network traffic over various servers or resources to improve system or network performance, reliability, and efficiency.

Specialized physical devices (hardware load balancers) are used to efficiently distribute network traffic across multiple servers or resources in a computing environment. These devices are purpose-built to handle the demands of load balancing, ensuring optimal performance, high availability, and reliability for applications and services.

Software load balancing improves system or network performance, stability, and efficiency by distributing incoming network traffic among several servers or resources using software-based solutions. Unlike Hardware load balancing, which relies on dedicated physical devices, software load balancing utilizes applications, services, or virtual machines running on standard servers to achieve Load balancing functionality.

The following table clearly compares the key differences between Hardware vs. Software Load balancing.

What is the difference between static and dynamic load balancers?

A static load balancer distributes incoming network traffic to a predetermined set of servers or resources based on a fixed configuration set by administrators. The traffic distribution is based on a defined algorithm (e.g., round-robin, least connections) and remains constant until manually modified. The configuration typically involves assigning specific servers to handle specific types or amounts of traffic.

A dynamic load balancer adjusts the distribution of incoming traffic based on real-time conditions and server loads. The traffic distribution is continuously monitored, and the Load Balancer dynamically reassigns traffic to servers based on server health, current load, or response times. This Load Balancer provides flexibility and adaptability to handle varying traffic patterns.

The following table clearly compares the key differences between Static and Dynamic Load Balancers. 

Load balancer use cases

A Load balancer is a vital component in modern computer networking that distributes incoming network traffic over numerous servers to guarantee that no one server becomes overloaded. Here are some examples of common load balancer applications:

Web applications and websites 

Load balancers distribute incoming HTTP/HTTPS traffic across multiple servers, improving website performance, enhancing response times, and ensuring high availability even during traffic spikes.

Media streaming and content delivery networks (CDNs)

Load balancers are crucial for distributing streaming media and content, optimizing delivery, reducing latency, and ensuring a seamless viewing experience for users.

Application delivery

Load balancers manage traffic for enterprise applications, including CRM systems, ERP platforms, and other business applications, ensuring consistent and reliable access for employees and clients.

eCommerce applications

Load balancers manage traffic for e-commerce platforms, distributing user requests across multiple servers to maintain a fast and reliable shopping experience, especially during peak times or promotions.

Gaming applications

Load balancers distribute traffic for online gaming platforms, ensuring low-latency connections, optimizing game performance, and evenly distributing the load during peak gaming times.

API services 

Load balancers distribute API requests evenly among servers, ensuring responsiveness, reducing latency, and preventing server overload, particularly in scenarios with high API requests.

Email services

Load balancers distribute email traffic to multiple email servers, ensuring efficient email delivery, optimizing processing times, and enhancing the reliability of email services.

High-performance computing (HPC) clusters

Load balancers distribute computing tasks across servers in HPC clusters, optimizing resource usage and ensuring efficient processing of complex computational workloads.

Microservices architecture

In a microservices environment, load balancers distribute traffic across various microservices to optimize resource utilization, maintain reliability, and ensure high availability for the entire application.

Bottom line

A load balancer will help you achieve any goal if you have outgrown a single web server or plan to do so. It will ensure your data and website remain highly available and operate optimally. Whether you're planning to deploy it yourself or looking for a managed system, you'll be better able to make decisions that benefit your organization if you understand your needs, current plans, and where you want to end up. 

Liquid Web provides customized load-balancing solutions to your unique requirements. Our team of experts can assist you in choosing the proper load-balancing setup that aligns with your business requirements and goals.

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About the Author

Mohammed Noufal

Mohammed Noufal is a B.Tech graduate with a decade of experience in server administration and web hosting. He is a father to two daughters and finds fulfillment in their growth. In his free time, he enjoys blogging, sharing experiences, and listening to music. With a strong technical background, family commitment, and creative outlets, he represents a well-rounded life journey.

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