Load Balancing. Benefits, Challenges, Types, Algorithms, and Tools

The idea of load balancing was first introduced in 1990 when specialized hardware was used to distribute traffic across a network. The invention of Application Delivery Controllers (ADCs), which guaranteed continuous access to applications even at peak times, made load balancing a more secure convenience.

Contemporary high-traffic websites must quickly and reliably respond to hundreds of thousands, if not millions, of user or client requests for the right text, photos, videos, or application data. Modern computing best practice typically necessitates the addition of extra servers in order to cost-effectively scale to handle these enormous volumes.

A load balancer serves as the "traffic cop" in front of your servers, distributing client requests across all servers equipped to handle them in a way that maximizes speed and capacity utilization and makes sure that no server is overworked, which can result in performance degradation. The load balancer distributes traffic to the active servers in case one server goes offline. The load balancer initiates requests to a new server when it is added to the server group.

In this article, we will introduce the following topics:

• Definition of Load Balancing

• Benefits of Load Balancing

• Challenges of implementing Load Balancing

• Load Balancing algorithms and how they work

• Types of load balancing

• Widespread use load balancing tools

• Best practices for load balancing

What is Load Balancing?

Load balancing commonly referred to as server farming or server pools is the process of efficiently dispersing incoming network traffic among a collection of backend servers. A load balancer is a software process, a virtualized instance operating on custom hardware or a real device. Regardless of where load balancers are located, they are utilized in ADCs to improve the speed and security of three-tier web and microservices-based systems.

A load balancer can employ a number of load balancing methods, including round-robin, server response time, and the least connection approach, to distribute traffic in line with the needs of the moment.

Why is Load Balancing Important?

Increased resource use, scaling, and high availability are all aided by a load balancer. You may specify the number of load-balancing criteria and application-specific health checks to ensure that the load balancer only serves traffic to healthy instances. Your maintenance window may be shorter if the load balancer can send traffic away from an application server that isn't working right before you turn it off for maintenance.

The following are the most typical reasons for using load balancing:

• Failover, High Availability: Load balancers prevent requests from being sent to inoperative servers during failover and high availability. Failure detection will determine how successful this is.

• Balancing Load: While it has an apparent name, the load is really the least understood, and many of its adverse effects are illogical. For example, the cost of SSL session negotiation may cause the servers' CPUs to work harder when the load is spread across several nodes. Similar to this, round-robin occasionally places an additional burden on all systems due to SSL session costs or a lack of HTTP keep-alive.

• Reducing Overload of Individual Nodes: While not a required result of effective load balancing, this is a very essential impact. For instance, rigorous round-robin balancing causes requests to be routed to a system that is overcrowded.

What are the Benefits of Load Balancing?

Network traffic load-balancing has several advantages for companies that manage numerous servers. The principal benefits of employing load balancers are as follows:

• Increased Scalability: Without disrupting services, load balancers extend the server infrastructure as needed to meet network needs. For instance, if a website starts getting a lot of traffic, traffic suddenly increases. The website goes down if the web server is unable to handle this unexpected surge of demand. To avoid this, load balancing distributes the excess traffic among several servers.

• Increased Effectiveness: The amount of traffic on each server is lessened, which improves network traffic flow and response times. Visitors to the website eventually have a better experience as a result.

• Reduced Downtime: Load balancing is advantageous for businesses with a worldwide presence and many sites in various time zones, particularly when it comes to server maintenance. To avoid service disruptions or downtime, a business might, for instance, shut down the server that requires maintenance and directs traffic to the other available load balancers.

• Predictive Analysis: Early failure identification and management is accomplished with the use of load balancing, without harming other resources. Software-based load balancers, for instance, foresee traffic bottlenecks before they occur.

• Effective Management of Failures: Load balancers automatically reroute traffic to working resources and fallback choices in the case of failure. For instance, load balancers transfer resources to other unaffected locations if a failure is discovered on a network resource, such as a mail server, to prevent service interruption.

• Increased Safety: Without needing additional modifications or resources, load balancers offer an additional layer of protection. A security feature known as offloading is being added to load balancers as more computing goes to the cloud. Redirecting attack traffic from the corporate server to a public cloud provider protects an organization from distributed denial-of-service assaults.

What are the Challenges When Implementing Load Balancing?

In order to resolve a number of problems and difficulties related to load balancing, extra consideration is needed. Here are some of the difficulties of load balancing implementation:

• Geographically Distributed Nodes: With cloud computing, data centers, and servers are geographically dispersed around the globe. In order to quickly process user requests, these scattered nodes are intended to be handled as a single location system. For tiny regions, some load-balancing methods are created. The distance between distributed nodes, communication delays, network delays, and the distance between the user and the resources are not taken into account. Nodes in remote places provide a problem since algorithms are ill-equipped to handle them in those circumstances. Algorithms that are suitable for nodes that are placed far away should be created and employed in this situation, according to one potential solution.

• Heterogeneous Nodes: To achieve efficient resource consumption and quick reaction times in cloud computing, customer needs should be implemented on diverse nodes since they frequently vary. The lack of effective algorithms for diverse contexts is a problem, though. To address this issue, further study is required.

• Virtual Machine Migration: Users construct several Virtual Machines (VMs) on a single physical system thanks to virtualization. These VMs are autonomous and have various settings. Certain VMs relocate to a different location utilizing the VM live migration technique if the physical computer becomes overcrowded. High bandwidth is required for the live virtual machine transfer. High delay results from the enormous VM image size being unable to be transferred at low bandwidths. In order to ensure that data is distributed fairly, filtering and reduction techniques help solve the problem of large workloads. This makes it possible to divide the job equally. By dynamically providing extra bandwidth for the VM to use, the network bandwidth issue is resolved.

• Scalability for Load Balancers: Users are able to use cloud services whenever they want thanks to its on-demand availability and scalability. In accordance with their demands, consumers can easily scale up or down the services. Consumer demands, compute requirements, storage needs, and system capabilities should all be met by an effective load balancer.

• Complexity of Algorithms: The performance of the entire system is significantly impacted by the load-balancing algorithms' complexity. The approach may look straightforward, but in terms of migration time, fault tolerance, and reaction time, it may yield poor performance. Regardless of the server load, load balancing techniques should be improved to give the greatest system performance.

• Storage Management: Modern cloud computing does not employ conventional storage systems, which call for expensive hardware and individual management. Data is stored on heterogeneous nodes using cloud computing, making accessing it simple. This sector is expanding quickly and needs data to operate effectively. Because of the regulation about duplicate data, full data replications are inefficient. While partial replication is sufficient, it is complicated in terms of load balancing and dataset availability. Effective load-balancing methods are required in order to distribute apps and other relevant data on a partial replication system.

What is Load Balancing Algorithms?

The logic behind a load balancer's method of allocating network traffic across servers is called a load balancing algorithm (an algorithm is a set of predefined rules). The two main methods for load balancing are as follows:

1. Dynamic load balancing: With dynamic load balancing, traffic is distributed based on algorithms that consider each server's present condition.

2. Static load balancing: Traffic is distributed using static load balancing without these modifications. Certain static algorithms, either in a predetermined sequence or at random, transmit an equal quantity of traffic to each server in a group.

Figure 1. Load Balancing Algorithms

1. Dynamic Load Balancing Algorithm

Dynamic load balancing algorithms are those that look for the network's lightest server and then place the proper load on it. The workload is split amongst the processors in this during runtime.

1. Least connection: Delivers traffic to the servers that have the fewest connections open at the moment after checking their status. This presupposes that the processing demands of each link are substantially equal.

2. Weighted least connection: Administrators are given the option to give each server a varying weight, based on the premise that certain servers can manage more connections than others.

3. Weighted response time: Determines where to send traffic by averaging the response times of each server and putting them together with the number of connections that each server has open. The algorithm guarantees that consumers receive speedier service by routing traffic to the servers with the shortest response times.

4. Resource-based: Loads are distributed according to the resources that are currently available on each server. Before directing traffic to a server, the load balancer asks specialized software (referred to as a "agent") running on each server to determine the host's available CPU and RAM.

2. Static Load Balancing Algorithm

Types of static load balancing algorithms are as follows:

1. Round robin: Using the Domain Name System (DNS), round robin load balancing delivers traffic to a number of servers in turn. Each time a DNS query is made, an authoritative nameserver will respond with a different A record from a list it has for the domain.

2. Weighted round robin: Lets an administrator give each server a varied weight. Servers that can manage more traffic will get a little bit more. DNS records allow for the configuration of weighting.

3. IP hash: Combines the source and destination IP addresses of incoming communication and creates a hash from it using a mathematical formula. The connection is assigned to a certain server based on the hash.

How Does Load Balancing Work?

A load balancing algorithm or technique is the preset pattern that the load balancer employs. This makes sure that no server is required to manage more traffic than it can handle. Several algorithms control the process in different ways. As a result, you have a wide range of alternatives when deciding which kind of load balancer to utilize.

Below are the fundamentals of a load balancer's operation:

• A client, such as an application or browser, gets a request and tries to connect with a server.

• When a load balancer gets a request, it directs the request to one of the servers in a server group depending on the algorithm's predetermined patterns (or farm).

• The connection request is received by the server, which then responds to the client via the load balancer.

• After receiving the answer, the load balancer compares the client's IP to the IP of the chosen server. The packet containing the answer is then forwarded.

• The process of decrypting data using the Security Socket Layer encryption protocol is known as SSL offload, and the load balancer handles it when it is necessary so that servers don't have to.

• Up to the end of the session, the procedure is repeated.

What are the Types of Load Balancing?

For your network, you may need to take into account a number of particular types of load balancing, such as SQL Server load balancing for your relational database, global server load balancing for troubleshooting across multiple geographies, and DNS server load balancing to guarantee domain name functionality. You can consider several cloud-based load balancers, such as the well-known Amazon Elastic Load Balancer while thinking about different load balancer types:

• Network Load Balancing: As its name implies, network load balancing uses network layer data to choose where to distribute network traffic. Layer 4 load balancing, which is made to accommodate all types of TCP/UDP traffic, is used to do this. Although network load balancing is thought to be the quickest load-balancing method, it frequently fails to evenly distribute traffic among servers.

• HTTP(S) Load Balancing: One of the earliest types of load balancing is HTTP(S) load balancing. This type of load balancing functions at the application layer since it uses layer 7. Because it enables you to base distribution decisions on any information that comes with an HTTP address, HTTP load balancing is sometimes referred to as the most versatile method of load balancing.

• Internal Load Balancing: It may be used to balance internal infrastructure. It is almost comparable to network load balancing.

It's vital to keep in mind that there are several kinds of load balancers, including virtual, software, and hardware ones.

• Hardware Load Balancer: Physical hardware, like an appliance, makes up hardware load balancers. They route traffic to servers based on factors such as the number of connections that are currently active, processor use, and server performance. Proprietary firmware is a component of hardware load balancers that needs upkeep when new versions and security fixes are issued. By providing a wider variety of capabilities like SSL hardware acceleration and Kerberos authentication, hardware load balancers often offer superior performance and control but need a certain degree of expertise for effective operation and maintenance. Because they are hardware-based, these load balancers are less flexible and scalable, hence there is a propensity to over-provision hardware load balancers.

• Software Load Balancer: Often, it is simpler to implement software load balancers than hardware counterparts. They work in combination with software development environments and have the added benefits of being more flexible and cost-effective. You have the freedom to configure the load balancer to meet the unique requirements of your environment thanks to the software approach. The increased flexibility could be at the expense of extra effort required to set up the load balancer. Software balancers provide you with greater ability to make modifications and updates than hardware ones, which take a more closed-box approach. Prebuilt virtual computers can be used as software load balancers (VMs). VMs will spare you some of the setting labor but may not give all of the functionality accessible with physical versions. Software load balancers can be purchased as cloud services, such as Load Balancer as a Service, or as installable systems that need configuration and administration (LBaaS). By opting for the latter, the cloud provider will take care of the regular upkeep, management, and upgrades of locally installed servers, saving you the trouble.

• Virtual Load Balancer: A virtual load balancer puts the software of a hardware load-balancing device on a virtual computer, setting it apart from software load balancers.

When Should I Use Load Balancing?

There are two frequently asked questions about local load balancing: "Do I have to do it?" the same "By when do I have to do it?"

Always, "yes" is the answer.

To begin with, let's define exactly what "local" load balancing means. Inside the data center, this is load balancing: receiving a request for one of the several servers hosting a web application, for instance. There is simply no justification for not doing local load balancing because it is an infrastructural essential.

Local load balancing is essential for the following two reasons:

• #1: To achieve high availability that can be sustained as you expand. For high availability, you require at least two backend servers, and your load balancer will make sure that if one backend is down, traffic is sent to the other backend. Although I'm going to concentrate on HTTP, the same principles apply to mail servers, devices that respond to incoming TCP data, and devices that get things from a backend work queue.

• #2: To establish a checkpoint in front of your services. The balancing or distribution of the load has nothing to do with this advantage. In fact, a load balancer would still be useful even if your service just had one backend. A control point gives you the ability to modify backends during deployments, provide filtering rules, and overall govern how your traffic flows. It enables you to modify the backend implementation of your service without disclosing those modifications to the users of your service on the front end. There may be a user inside the data center, a client outside the facility, or even another service.

What are the Tools for Load Balancing?

Using a load balancer (LB) is one of the quickest and simplest ways to set up an application with high availability and boost performance.

There are three main categories of load balancers.

1. Hardware-based

2. Cloud-based

3. Software-based

A specialized device for load distribution and its associated characteristics is a hardware load balancer. Among of the well-known LB hardware suppliers are:

• F5

• TP-Link

• Barracuda

While pricey, they allow you total control.

More than ever, cloud load balancers are in vogue.

One of the most economical methods to use all of the functions without spending money on a physical device is to use cloud LB. What you use, you pay for. These are some of the well-known cloud load-balancing providers:

• AWS

• Cloudflare

• Cloud Google

• Incapsula

• Digital Ocean

• Azure

The information below will be helpful if you don't have money or want to look into a load balancer that is free.

• Traefik: According to Traefik, it is the "cloud native edge router." It is a Golang-based reverse proxy and load balancer for contemporary microservices applications. Traefik is a top option for container-based microservices architectures because of its concentration on support for a number of contemporary container orchestration systems, batteries-included logging, and multiple widely used metric formats.

• Seesaw: A trusted Linux-based virtual load balancer server is employed by Google to offer the required load distribution on the same network. Go-developed Seesaw runs smoothly on the Ubuntu/Debian operating system. It needs two Seesaw nodes, supports anycast, and DSR (direct server return). They might be virtual or real. It's important to note that Seesaw only supports layer four networks, thus if you need layer seven load balancing, you might want to consider alternative solutions.

• KEMP: On all significant hypervisors, a complementary sophisticated application delivery controller from KEMP is supported. Either you can download it and use it in your own data center, or you can put it in a cloud data center like Amazon or Azure. Several of the top companies, like Apple, Sony, JP Morgan, Audi, Hyundai, and others, employ KEMP LB. The free edition gives sufficient functionality; but, if you need more, you may check out their commercial license. Even though it's free, it has premium features like the ones listed below.

  • TCP/UDP layer 4 load balancing utilizing least-connection or round-robin algorithms
  • Layer 7 balancing
  • Put a web application firewall (WAF) in place
  • Inside intrusion detection system (IPS)
  • Real-time, multi-site load balancing for servers
  • Caching, content switching, and content compression
  • Website cookie endurance
  • IPSec tunnel
  • Pre-authentication
  • let's encrypt.
  • Kubernetes

• NGINX: Everyone working in web application engineering ought to be familiar with the moniker Nginx right away. Via the ngx_http_upstream_module of this tool, load balancing capabilities are provided. Nginx is a well-known, extensively supported alternative that provides incredibly scalable performance right out of the box and can be expanded with other modules like Lua.

• Gobetween: Gobetween is a high-performance, L4 TCP, TLS, and UDP-based load balancer that is simple yet effective. It functions on a variety of operating systems, including Windows, Linux, Docker, and Darwin, and if you're interested, you can build from the source code. Go-between appears intriguing if you're seeking a cutting-edge L4 balancing solution with auto-discovery for the dynamic environment. Try it out and see how it works.

• Zevenet: Zevenet is a well-liked open-source load balancer that many companies use to strengthen their online infrastructure and has established itself as one of the best options for reducing response. Due to its superior performance as an Application Delivery Controller (ADC) and network and service optimizer, this load balancer has been gaining popularity. The Zevenet load balancing solution has always been known to give its customers the automation of scalable infrastructure because of the complete interoperability of their solution through API. It is suitable for users across industries, including those in education, health care, telecoms, and entertainment, among others. It has a sophisticated intrusion prevention and detection system that can guard against DDoS in real time at both the networking and application levels.

What are the Best Practices for Implementing Load Balancing?

Some of the best practices for implementing load balancing are listed below:

• It is crucial to configure and size load balancers properly in order to prevent performance reduction or bottlenecking. Verify that the load balancer can handle the maximum transaction rate and bandwidth so that it does not impede peak performance (based on PUT/GET).

• Install redundant load balancers (as per manufacturer's specifications) to eliminate single points of failure.

• Use DNS Round Robin only if you are unable to deploy Global DNS or Load Balancing because it is a superior strategy.

• For optimal performance, close SSL connections at the load balancer(s) and send traffic.

• Use just the load balancer's high availability features for NFS traffic.

• Enable traffic monitoring on the web.

• The network latency between your users or client apps and your workloads (load balancer backends) will decrease as their proximity increases.

• As part of your default, global external HTTP(S) load balancer setup, enable Cloud CDN and caching.

• Consider selecting the backend service for each new connection based on which backend is the most responsive in order to improve performance. The RATE balancing mode can be used to do this.

• In some circumstances, it could be advantageous for the same backend to handle requests coming from or connected to the same end user, at least temporarily. Session affinity, a setting on the backend service, may be used to configure this.

• Implement multiple load balancers. To achieve high availability, it is essential to use numerous load balancers in a load-balancing cluster.

• Implement health checks to make sure that traffic is only sent to healthy servers by the load balancer. If a server becomes unhealthy, the load balancer should cease transmitting traffic to that server.