Ronald Caldwell Websites and applications with a large amount of traffic will benefit from load balancing. We will dive into what it is, the methods of load balancing, its benefits, and its uses for load balancing.
This article will focus on balancing hypertext transfer protocol (HTTP) and hypertext transfer protocol secure (HTTPS) traffic through a load balancer.
What is load balancing?
Load balancing is the distribution of website or application workloads across multiple servers (sometimes called nodes). Traffic is intelligently distributed across these servers to a single IP using different protocols.
As a result, the processing load is shared between the nodes rather than being limited to a single server, increasing the performance of your site or application during times of high activity.
Load balancers are implemented via hardware or software. For example, in web hosting, load balancing is typically used for handling HTTP traffic over servers acting together as a web front-end. The web front-end comprises the graphical user interface (GUI) of a website or application.
Load balancing also increases the reliability of your web application or website and allows you to develop them with redundancy in mind. If one of your servers fails, the traffic is strategically distributed to your other nodes without interruption of service.
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.
- Request is received: When a user sends a request (e.g., visiting a website), the load balancer intercepts it and evaluates how to handle it.
- Request is routed: Using predefined algorithms and real-time data—like server health, response time, or location—the load balancer directs the request to the server with the best resources for the request origin.
- Intelligent monitoring: The load balancer continuously checks server performance. If a server fails, it automatically reroutes traffic to healthy servers to maintain uptime and performance.
Think of load balancing as a host at the front desk of a restaurant. The host seats guests (client requests) at different tables (servers) based on availability. If one table is full, they redirect guests to another that fits their party, keeping service smooth.
Methods of load balancing
There are different algorithms used to balance your traffic that are either static or dynamic. Each has advantages and drawbacks.
Static load balancing
With static load balancers, traffic is distributed based on predefined rules or fixed parameters—there’s no real-time decision making. While algorithms can be tweaked, it’ll run with minimal maintenance in a healthy server environment.
Round robin
With the round robin method, the load balancer will send traffic to each server in succession. Round robin is most effective on equally-configured web servers and when concurrent connections are not extremely high. 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.
Round robin doesn’t check if a server is already busy or slow—so some servers might get overwhelmed while others stay underused. It works best when all of the server hardware in the infrastructure has comparable computational power and capacity.
Weighted round robin
This is a type of round robin that assigns more requests to higher-capacity servers based on weight values. For example, a server with twice the power may receive twice the traffic.
Source IP hash
Source IP hashing is a load balancing method where each visitor’s IP address is used to decide which server they connect to. Each visitor is giving a distinct key, so they are always routed to the same server—even if they disconnect and reconnect.
As Citrix notes, this approach helps reduce latency and optimize CPU usage—especially valuable for high-traffic applications and websites.
URL hashing
URL hashing is a load balancing method that routes requests based on the URL being accessed. Requests with the same URL are always sent to the same server, which helps keep things consistent—like user sessions or cached content.
It’s especially useful when specific pages or routes need to stay tied to a particular server for performance. Similar to source IP hashing, URL hashing ensures consistent routing—but instead of using the visitor’s IP, it uses the URL itself to generate the key.
Dynamic load balancing
With this load balancing method, dynamic algorithms monitor server health and performance in real time, routing traffic based on current conditions like connection count, response times, or system resources.
Least connection
The least connection method considers the current number of open connections between the load balancer and the server. It sends the traffic to the node with the lowest number of active connections. It’s most effective with higher concurrent connections and more intelligent than the round robin method, but still does not consider the current load or responsiveness of the nodes.
Weighted least connections
The weighted least connections algorithm, also available with the round robin method, allows each server to be allocated a priority status. If one server has more capacity, it gets a higher weight, so the load balancer sends it more requests—especially when two servers are equally busy. This helps prevent overloading smaller servers.
Least response time
The least response time method decides which node to send the traffic to using the current number of open connections between the load balancer and the server and the response times of the nodes. The node with the lowest average response time and the fewest number of active connections receives the traffic.
Least pending requests (LPR)
Least pending requests (LPR) sends traffic to the server with the fewest queued requests. By always picking the server that’s the least busy, it helps handle traffic spikes smoothly, speeds up response times, and keeps resources running efficiently
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.
Custom methods
Custom load balancing uses rules tailored to your application’s needs to decide how traffic is distributed across servers. It gives you the flexibility to optimize performance based on exactly what matters most—like CPU usage, memory, or user behavior. It typically requires a load monitoring system and is tailored to your application’s specific needs.
Benefits of load balancing
By nature, load balancing solves more than one problem:
- Unexpected traffic spikes.
- Growth and popularity over time.
Here are some additional benefits of load balancing.
Scalability
As your website or application grows, your load-balanced infrastructure grows with you. Add additional web server nodes to increase your capacity to handle the added traffic.
Redundancy
Your web front-end is replicated across your web servers, giving you redundancy in case of node failure. The remaining servers handle your traffic if an issue occurs until the failed node is repaired or replaced.
Flexibility
The fact that there are several load balancing methods means that options abound for managing traffic flow. You have the flexibility to choose how you want incoming requests to be distributed.
Drawbacks of load balancing
While there are a lot of benefits to load balancing, there are some disadvantages as well.
Misdirected traffic
The method or algorithm of load balancing that you choose may not consider the nodes’ current load, open connections, or responsiveness. This lack of consideration means that the node receiving the traffic could already be under significant load, have little to no available connections, or be unresponsive.
Additional configuration
Another drawback is the possibility of additional configuration depending on the implementation of your load-balanced infrastructure. For example, it may be necessary to maintain concurrent connections between website/application users and servers. Also, as servers are added or removed, you will need to reconfigure the load balancer.
Associated costs
There are additional costs associated with hardware-based load-balanced infrastructure. For example, you will need to account for the cost of additional servers for the dedicated load balancer and the web nodes.
Types of load balancing
Various types of load balancing operate at different layers of the network stack. Here’s an overview of the primary types.
Layer 4: Network load balancing
Network load balancers operate at the transport layer (Layer 4), distributing traffic based on IP addresses and TCP/UDP ports without inspecting the content of the packets
Layer 7: Application load balancing
Operating at the application layer (Layer 7 of the OSI model), application load balancers make routing decisions based on content within the HTTP/HTTPS requests, such as URL paths, headers, or cookies.
DNS load balancing
DNS load balancing distributes traffic by associating a single domain name with multiple IP addresses. When a user requests the domain, the DNS server responds with one of these IP addresses, directing the user to a specific server.
Cloud load balancing
Cloud load balancing leverages cloud provider infrastructure to distribute traffic across multiple servers or regions, offering scalability and high availability.
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.
Hardware load balancers are physical devices designed to efficiently distribute traffic across servers, helping ensure high performance, availability, and reliability for applications.
Software load balancing distributes incoming network traffic among several servers or resources using software-based solutions. Unlike hardware load balancers, software load balancer solutions run on standard servers or in the cloud, offering greater flexibility, easier scalability, and lower upfront costs.
Load balancing use cases
Reduce downtime
The redundancy of load balancing allows you to limit the points of failure in your infrastructure. Doing so increases your uptime. For example, suppose you load balance between two or more identical nodes. In that case, if one of the nodes in your Liquid Web server cluster experiences any kind of hardware or software failure, the traffic is redistributed to the other nodes to keep your site up.
If you are focused on uptime, load balancing between two or more identical nodes that independently handle the traffic to your site allows for failure in either one without taking your site down.
Plan for future growth
As your site gains popularity, you will outgrow the power of even the most robust servers and require something more substantial than a single server configuration. Load distribution helps you grow beyond a single node.
Upgrading from a single server to a dual server configuration (one web server and one database server) will only allow for so much growth. It is useful when your backend database is receiving a ton of requests and needs its own resources to handle them. When the issue is related to the front-end, load balancing the traffic will aid in the growth you are experiencing.
Predictable and actionable analytics
More than directing traffic, software load balancers give insights that help spot traffic bottlenecks before they occur or become more significant issues. Being able to see where traffic is or potential holdups will save time and money. In addition, it gives you actionable predictions and analytics that help you make informed business decisions.
Choosing the best method for you
The most appropriate choice in load balancing algorithms depends on the needs of your website or application. If your site is experiencing slow performance due to concurrent connections, it is worth exploring load balancing options.
Liquid Web has load balancing, dedicated server options, and more available. Consult with our solution architects and hosting advisors to answer any questions about what is best for you. Schedule a call today!
