What Is a Load Balancer? Types, Features, and Functionality

What Is A Load Balancer

A load balancer is a type of server-based technology that distributes incoming internet traffic across multiple servers to make sure no single server gets overwhelmed. You’ve probably experienced real-life load balancing at a public event, such as a festival, when everyone is looking for a space to park. Someone, usually a parking attendant, controls traffic to prevent a snarl-up.

The most common reason for load balancing is to prevent too much traffic from going to an already overwhelmed server. If such traffic isn’t regulated, it can slow down or even crash the website.

This article covers the basics of load balancers and dives deep into specifics such as types of load-balancing algorithms, key features, strategies, future trends, and more.

Understanding Load Balancers

Load balancers distribute incoming traffic across a network of servers to make sure that no single server carries too much load.

Graphic displaying load balancer diagram
A load balancer evenly spreads out different devices, such as computers, tablets, and phones, across specific servers to efficiently share network traffic.

Load balancers continually assess the demands on each server in terms of incoming traffic and direct user requests to servers that are not overloaded. This process helps prevent slowdowns and crashes.

Types of Load Balancers

While load balancers may all seem to have the same way of doing things, they are different from each other. To give you an idea of what I mean, let’s look at the different types of load balancers and what they do.

  • Hardware load balancers: These are physical devices designed to efficiently manage and distribute network or application traffic across multiple servers. You’ll find them mostly at large enterprises and data centers because they are good at handling high traffic volumes and have strong processing power.
  • Software load balancers: Software load balancers are not tied to physical devices. They are actual software installed on the server. That means you can adjust, upgrade, or configure them through software updates. You’ll find these load balancers in dynamic environments where traffic patterns frequently change because they’re highly flexible and scalable.
  • Cloud-based load balancers: One reason people choose cloud hosting over other types of hosting is because it is highly scalable. However, most people don’t know that load balancers massively contribute to the scalability of cloud hosting. It’s one of the unsung heroes that works tirelessly in the background to make cloud hosting the people’s favorite scalable hosting solution.

Keep in mind that although load balancers serve the same primary purpose – load balancing – not every one of them will fit into your project. Software load balancers, for instance, are relatively more affordable because they’re actual software, not physical units.

Hardware load balancers are physical machines, which makes them more expensive to maintain. Finally, cloud-based load balancers are service-based solutions provided by cloud platforms and integrated with the cloud infrastructure. What this means is that they don’t require separate hardware devices or software installations on local servers.

Key Features and Functionalities

Now let’s check out some of the most important features of load balancers and how they function. This should give you a better idea of how this technology works in general.

Load Balancing Algorithms

At the heart of every load balancer are the algorithms that determine how to distribute traffic across the available servers.

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Algorithms are sets of rules computers follow when executing tasks.

You’ve probably heard this term in relation to social media algorithms. For example, if you search for a local therapist online, you’ll likely start seeing therapy-related ads on your social media. That right there is an algorithm at work.

Load balancing algorithms, such as the round-robin algorithm, tell the system to alternate traffic to each server in a rotation.

Health Checks and Monitoring

Part of the load balancing process involves performing health checks and continuous monitoring of the backend servers.

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Think of it this way: You wouldn’t ride a sick horse, right?

The same logic applies to the load-balancing process. It checks whether the servers are healthy.

If one server starts to fail or responds too slowly, the load balancer temporarily pulls it out of the rotation and reroutes traffic to healthier servers.

SSL Termination and Encryption Offloading

SSL termination involves decrypting incoming SSL/TLS connections. That’s also one of the things load balancers are good at. To understand this, let’s first go over the SSL termination and encryption process and what it’s all about.

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Imagine a situation where you handle all mail sent to your 90-year-old grandma’s house. You receive the mail, open it, and then read it out loud to her.

That means she won’t have to struggle to open the mail, find her reading glasses, or figure out who the sender is in the first place. That’s the job of load-balancing technology. It receives the mail in secure form, offloads the encryption (opens it and reads its contents), and then passes the message on to the server (your grandma, in this case).

These features make load balancers an indispensable tool in managing web traffic. They ensure that a website can handle high volumes of requests without compromising on performance.

The Role of Load Balancers

One does not simply talk about load balancers without mentioning these two words: scalability and performance. In fact, we can argue that these two are the primary reasons we implement load-balancing technology in the first place. Below, I’ll explain the kind of role this technology plays and how it contributes to scalability and performance.

Scalability Challenges in Digital Infrastructure

As of January 2024, there were about 5.3 billion internet users in the world. This means that more than half of the global human population, which stands at about 7.9 billion, has access to the internet.

As more users come online, handling increased traffic is one of the things that give web administrators sleepless nights. When a website or application receives more traffic than expected, it can slow down significantly or even crash if it’s not equipped to scale up efficiently.

That’s where load balancers step in to manage large volumes of requests and maintain high availability and reliability. This eventually prevents bottlenecks and potential service disruptions.

Needless to say, no one loves visiting a website or web application that’s always offline. Search engines won’t even bother ranking such websites on the first page if they’re not consistently online.

How Load Balancers Optimize Performance

Scalability aside, let’s focus on the second aspect that makes load balancing quite a big deal in web hosting technology. I’m talking about performance.

  • Distributing traffic across multiple servers: By intelligently distributing incoming traffic across multiple servers, no single server takes on more than it can chew. As we saw earlier, this distribution occurs through various algorithms that assess each server’s current load and capacity.
  • Scaling resources dynamically: As demand (i.e. traffic) increases, load balancers can automatically add more server resources to handle the load. But here’s the trick: These resources don’t just get stuck out there, doing nothing when traffic slows down. They scale back down when demand decreases. It’s like the U.S. Army Reserve; they only swing into action when needed.
  • Mitigating downtime and improving response times: As you’d expect, by continuously monitoring the health of servers and rerouting traffic away from servers that are down or underperforming, load balancers reduce downtime risks and increase response times. That’s because the algorithms only send requests to servers that are currently performing well.

It’s almost impossible to imagine a server running without load-balancing technology. That’s a recipe for disaster. This technology can single-handedly improve user experience, performance, and potentially even search engine rankings.

Load Balancing Strategies and Algorithms

As we saw earlier, load balancers are a form of server-based technology. But load balancing, on the other hand, is more of a strategy guided by algorithms, if that makes any sense. If you’re a little bit confused about this whole setup, no worries. Things will become a little bit clearer as you keep reading this article.

Overview of Algorithms

Load-balancing algorithms come in two forms: dynamic and static. Here’s what these two types of algorithms are good for.

Dynamic Load Balancing Algorithms

Dynamic load balancing algorithms are sophisticated in that they adapt to changes in real time, just as you’d expect from anything that’s considered dynamic. They adjust traffic distribution based on current server loads and conditions. Here are some key dynamic load-balancing algorithms:

  1. Least Connection: Least connection looks for the server with the fewest active connections and then directs extra traffic to those servers. This algorithm works best in environments with varying session lengths since it provides a more even distribution of long and short tasks across servers.
  2. Weighted Least Connection: This algorithm first considers the capacity of each server to determine what it can handle. It then assigns heavier loads to servers with higher capacities, perhaps due to better hardware or less intensive tasks.
  3. Weighted Response Time: Here, the algorithm looks around to find a server with the best response time and capacity and then assigns it the extra load. Think of it as your boss assigning you more tasks because you’ve turned in the previous task earlier than expected. In other words, you have a faster response time than your coworkers.
  4. Resource-Based: A resource-based algorithm looks at each server’s actual resource usage, such as CPU and memory utilization, to determine where to route new requests. It works best in an environment where different requests might have different resource requirements. For example, the number of resources needed to load a webpage that consists of plain text isn’t the same as what the server will need to load, say, a video game.

Static Load Balancing Algorithms

Static load balancing algorithms are exactly what they sound like. They divide traffic equally among servers meaning they don’t change their server selection strategy based on current traffic or server status. This quality makes them simpler to implement, but you won’t get the same level of flexibility as you would with dynamic algorithms. Static load balancing algorithms are intended for systems with very little variation in load.

  1. Round Robin: This is one of the simplest forms of load balancing. It circles around a list of servers and distributes each new request to the next server in line. It thrives in environments where all requests have similar resource demands.
  2. Weighted Round Robin: This strategy works almost like its variant round robin, but the key difference is that it assigns a weight to each server based on its capacity or expected load-handling ability. The heavier the server, the more requests it handles.
  3. IP Hash: This algorithm uses the IP address of the incoming request to determine which server will handle the request. As a result, it consistently sends a particular user to the same server.

Note that these algorithms work for different environments. So, when do you decide to opt for static or dynamic load-balancing strategies? That brings us to our next topic.

Choosing the Right Load Balancing Strategy

You can only experience and appreciate the power of load-balancing technology if you choose one that’s best for your unique needs. Three things should always be at the top of your list: application architecture, performance implications, and the nature of the environment you want these load balancers to operate in.

Considerations Based on Application Architecture

In this context, I’m using the word “architecture” to describe the overall structure of your application. What does it look like? What does it need to operate? What does it aim to achieve? Where do you want it to operate?

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For instance, let’s say your application operates across multiple geographic locations. In that case, a global load balancer may be necessary.

Similarly, applications built on microservices architectures may require more dynamic load balancing because they’ll handle numerous processes at the same time.

An eCommerce platform is a good example of such an application. It handles order listings, processing, returns, refunds, shipping, and more, all under one roof.

Performance Implications of Different Algorithms

By now, you know each balancing algorithm comes with its own set of performance implications.

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We’ve seen that simple algorithms like round-robin are easy to implement and manage but may not handle uneven load distribution well because they tend to have a static mind.

On the other hand, sophisticated algorithms like weighted least connection or weighted response time can provide better performance by considering current server load and response times.

The biggest drawback here is that they require more complex configuration and monitoring. They are also more expensive to maintain.

Balancing Traffic Efficiently in Diverse Environments

You should have a rough idea of the kind of network traffic you expect. For instance, environments with highly variable traffic will need a load balancer that supports dynamic scaling and real-time health checks.

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These balancers prevent servers from becoming overwhelmed during peak times and underutilized during off-peak times. Instead, they offer a balance between these two environments.

Ultimately, what works for you won’t work for another person. That’s because we all have unique needs.

Do your homework before choosing the right load-balancing technology. While you’re at it, pay special attention to the three areas I’ve covered above.

Load Balancers in Digital Infrastructure

We’ve seen how load balancers work. Now let’s talk about implementing this technology in your digital infrastructure.

Setting up a Load Balancer

The first thing you need to do is consider both configuration and deployment options to make sure they fit your existing setup. Decide whether you need hardware, software, or cloud-based balancers.

Once that’s out of the way, you now need to set things up. Here, you’ll define how to distribute traffic across your servers. This could mean setting up specific rules for traffic routing, choosing the right load-balancing algorithm, and connecting the load balancer to your network in a way that optimizes performance and security.

Best Practices for Configuration

To get the most out of your load balancer, you should make sure the setup adheres to the best practices. Here are some tips to keep in mind:

  • Set appropriate intervals for health checks to ensure problem servers are quickly identified and traffic rerouted.
  • Manage your timeouts to strike a balance between giving a server enough time to respond and preventing a slow response from affecting overall performance.
  • Set up proper SSL termination to offload this task from your servers and maintain fast response times while keeping transmissions secure.
  • Implement regular monitoring and dynamic scaling strategies as a way to respond to changing traffic loads and maintain optimal performance.

When you implement these best practices in your setup, you’ll have an environment that not only provides optimal performance but also works harmoniously with other existing server technologies.

Load Balancers in Cloud Computing Environments

Cloud computing is perhaps one of the best environments for witnessing the power of load balancers in action. Here’s why this environment stands out.

The Role of Load Balancers in Cloud Architecture

In cloud computing environments, we use load balancers to effectively manage traffic and resource distribution. Most major cloud providers, including the gigantic trio of Amazon Web Services (AWS), Microsoft Azure, and Google Cloud, have built-in load-balancing technologies that integrate seamlessly with other cloud services.

For example, at AWS, load balancers integrate well with Amazon Elastic Compute Cloud (EC2). When you head over to Microsoft Azure, you’ll find its load balancers working hand in hand with Azure Virtual Machines. At Google Cloud, this technology teams up with Google Cloud CDN and Google Kubernetes Engine to create the dream partnership.

Challenges and Considerations in Cloud Load Balancing

It’s not all sunshine and rainbows in the cloud; implementing load balancers in cloud architectures comes with its fair share of challenges and considerations. For example, you may need to think about network latency and data transfer costs. That’s because inefficient load balancing can lead to increased latency and higher costs as data travels across different regions or between zones.

Additionally, you must make sure that the load-balancing technology (or sometimes even the strategy itself) works with cloud-native applications. Don’t assume that you’ll just plug in any technology, hit the play button, and watch the magic happen.

Remember that cloud-native applications are naturally scalable and resilient. So, if you’re going to add a load balancer as part of your cloud adoption strategy, it must be capable of integrating with the application without disrupting its native behaviors.

Security Considerations

The security aspect of load balancing is often overlooked but equally important. Here’s what you should know.

Load Balancers as a Security Tool

Load balancers don’t just distribute traffic, improve performance, and then call it a day. On top of these functionalities, they also help protect against security threats.

You can use this technology to mitigate Distributed Denial of Service (DDoS) attacks by handling unexpected traffic spikes, which can take down unprepared systems. Spreading these loads across multiple servers using load balancers is one way of preventing any single server from being overwhelmed. This strategy helps maintain service availability even under attack.

Did you know? You can use load balancing to set up access controls and apply firewall rules restricting unauthorized access. It can filter out malicious traffic before it reaches your servers.

SSL Offloading and Encryption Best Practices

We’ve already discussed how load balancing helps secure data in transit and relieves backend servers of the burden of offloading encrypted data. But don’t assume that this is a one-man show; you need to manage SSL certificates and implement key rotation practices to maintain strong server security standards.

When you regularly update SSL certificates and keys, you prevent the exploitation of potentially compromised keys. This is also a good way to protect encrypted communications against third-party interception.

The beauty of technology is that it keeps evolving. And load balancing is not immune to this change. Here are my predictions for future load-balancing trends and innovations.

Emerging Technologies and the Future of Load Balancing

Machine learning is now more relevant than ever since ChatGPT popped onto the scene. Artificial Intelligence (AI) is the talk of town. And it’s not all talk without action — this technology is reshaping how we interact with machines (or rather, how they interact with us).

I’m predicting a future where load-balancing technologies become even smarter and more effective, all thanks to the power of AI. A good example of such an approach to load balancing is predictive analytics.

Line graph displaying predictive analytics market size 2024-2032
The predictive analytics market has a CAGR of 21.4%, while the AI market is projected to grow even faster, with a CAGR of 36.6%. Could the two eventually coincide? (Source: Precedence Research)

Load balancers can now predict traffic patterns and adjust resources proactively rather than reactively. It’s like having a police officer who can predict and stop crime before it occurs compared to one who reacts to crime by making arrests after the damage has already been done. The former will always be the better option.

Addressing Challenges in Microservices Architectures

One of the biggest challenges facing microservices and containerized environments, as far as load balancing is concerned, is that these architectures can dynamically change, scale, and move across a cluster. What this means is that they’ll end up demanding more adaptive load-balancing strategies.

Implementing dynamic routing and service-to-service security within containerized architectures is one way of solving this challenge. With this technology, it’s possible to manage inter-service communications and provide built-in load-balancing capabilities that can detect and route requests intelligently at the individual level instead of the whole architecture.

Think of a popular eCommerce platform like Amazon, for example, during the holiday season. Chances are, the order processing section of the platform gets busy around that time, followed by the deals section, among others. Built-in load balancing would focus on specific sections that are busy at the time rather than on the entire platform.

Beyond Traffic Management: Harnessing the Power of Load Balancers

That, folks, is load balancing 101. We’ve learned that this technology helps optimize performance and make web servers even more reliable. A reliable and available server means a better user experience.

Similarly, a better user experience leads to higher chances of success for whatever goal you have in mind, be it boosting sales, views, subscriptions, clicks, or anything in between. But as time goes by and technology continues to evolve, we’re beginning to notice a trend where load balancers are doing more than initially intended.

For example, load balancing is now part of server security strategies since they help block DDoS attacks. And with the rise of AI, this technology will only get smarter and assume even bigger roles regarding server performance, scalability, reliability, and security.