An Introduction to Load Balancing

What is Load Balancing?

In simple terms, load balancing is a way to spread tasks out over multiple resources. By processing tasks and directing sessions on different servers, load balancing helps a network avoid annoying downtime and delivers optimal performance to users. How this is accomplished varies between networks. There are virtual load balancing solutions that work in a manner similar to virtual applications or server environments. There are also physical load balancing hardware solutions that can be integrated with a network. The method used depends entirely upon the team implementing the solution and their particular needs.

Types of Load Balancing Methods?

There are different variations of load balancing. Link load balancing (learn more about load balancing solutions), SIP load balancing, network load balancing and server load balancing are among the most common forms. These load balancing forms operate on the same basic principle - distributing tasks and processing among servers to ensure availability and performance. They are found in both hardware and virtual solutions.

Load balancing configurations can vary between organizations. Some will operate by spreading pre-defined groups of users over specified servers. Others, more commonly, will split users across servers as they visit the system. The latter approach provides more flexibility and more effective load balancing in a dynamic environment, whereas the first approach is used more often on intranets.

Splitting the users across multiple servers can be accomplished with a load balancing hardware solution or a virtual load balancing appliance. If a physical piece of hardware is used for load balancing, the load balancer will route users to different local physical servers. This is sometimes known as "direct server return", as the information from the servers goes directly to users instead of returning through the load balancing device. There are other methods of physical load balancing as well - including tunneling and IP address translation.  

Read more about load balancing hardware and software differences here. 

A load balancing software solution works slightly differently. In this scenario, the load balancing software emulates a server, and then forwards the traffic to the real servers. These solutions require more processing power than a physical device, but offer more options for security and configuration.

The blog Webhosting Geeks offers a guide for those looking to find a load balancing technique appropriate for their site.

Radware offeres multiple types of load balancing solutions, including:

How does load balancing work?

In order to distribute the necessary tasks, load balancers go through a series of steps. First, the load balancer will query the available servers to ensure their availability. The load balancer pings a server, and if the expected response occurs, it will be included in the available list. If the server fails to respond, it will not be used until another test is performed and it returns with the appropriate response. Load balancing software is very flexible in this environment, as the administrator can quickly tweak the system to ensure it is checking servers appropriately and accurately.

Distributing the load between the active servers can be done in several different ways. The load balancer may use a round-robin method, where each server is used in turn. It can also use a weighted round robin system, where servers are assigned traffic based on their configured capabilities.

Load balancing methods will vary greatly between different networks and organizations depending on the needs of the organization and the equipment available to perform the task. Radware experts can help you with the specific requirements for your system.