What is Load Balancing and How Does a Load Balancer Work

Wondering what is load balancing and how can a load balancer work? In this ultimate guide to load balancing, get to know all the knowledge about load balancing you are curious about, including the definition, types, and working principles of the load balancing tech.

What is Load Balancing

What is load balancing? It is a method of distributing network traffic among a group of servers known as a server farm. It improves network performance, stability, and capacity while lowering latency since demand is divided evenly across several servers and computer resources.

Load balancing uses a physical or virtual appliance to determine in real time which server in a pool can best handle a particular client request while ensuring that heavy network traffic does not overwhelm a single server. Load balancing enables failover in addition to maximizing network capacity and assuring excellent performance. When one server fails, a load balancer rapidly shifts its workloads to a second server, reducing the impact on end users.

Load balancing is typically classified as supporting Layer 4 or Layer 7 of the Open Systems Interconnection (OSI) communication paradigm. Transport data, such as IP addresses and TCP port numbers, is used by Layer 4 load balancers to distribute traffic. Layer 7 load-balancing devices make routing decisions based on application-level features such as HTTP header information and the message's actual contents, such as URLs and cookies. Although Layer 7 load balancers are more ubiquitous, Layer 4 load balancers are still widely used, particularly in edge installations.

How Does a Load Balancer Work

After learning what is load balancing, let’s check the working principle of load balancers. There are several techniques to implement load balancing. Physical appliances that are installed and maintained on-site are hardware load balancers. Applications known as software load balancers can be found on privately owned servers or as managed cloud services (cloud load balancing).

In either scenario, load balancers function by instantly deciding which backend servers are most equipped to handle incoming client requests. The load balancer distributes requests among any number of accessible servers, whether they are hosted on-site, in server farms, or in cloud data centers, to avoid overloading a single server.

The assigned server responds to the client via the load balancer after receiving the request. When the IP addresses of the client and the chosen server match, the load balancer completes the server-to-client connection. Once this happens, the client and server can interact and perform activities until the session is over.

A load balancer may bring more servers online to meet demand if network traffic surges. Or, if there is a drop in network activity, the load balancer may decrease the number of servers that are readily available. Sending traffic to cache servers where past user requests are momentarily held can also help with network caching.

Types of Load Balancer

Apart from knowing what is load balancing, it is also necessary to know the types of load balancers to better utilize it. Different load balancer types can be deployed with varying storage capabilities, functionality, and complexity levels depending on the needs of a network. A load balancer can be a software instance, a physical appliance, or a hybrid of the two. Generally, there are two different categories of load balancers:

1. Hardware load balancer. A hardware load balancer is a piece of hardware with proprietary, specialized software integrated into it that is made to handle high application traffic volumes. These load balancers allow for the use of several virtual load balancer instances on a single device due to their built-in virtualization functionality.

Traditionally, suppliers would install proprietary software on specialized hardware before selling it to customers as a standalone appliance, usually in pairs to enable failover if one system fails. A business must buy more or bigger gadgets to accommodate expanding networks.

2. Software load balancer. Application delivery controller (ADC) functions such as software load balancing are typically run on white box servers or virtual machines (VMs). Caching, compression, and traffic shaping are common extra functions offered by ADCs. Virtual load balancing is used in cloud systems and has a lot of versatility. Users can automatically scale up or down, for instance, to reflect traffic peaks or a decline in network activity.