The rise in internet traffic in the early 1990s led to the advent of the load balancer. Initially designed to consolidate server resources and distribute traffic fairly, load balancers have evolved taking on different avatars in the past three decades. Initially, they operated at the network layer and regulated connections by scrutinizing the five-tuple (source and destination IP addresses, source and destination ports and the IP protocol). This marked the emergence of the network server load balancers, also known as Layer 4 load balancers.

Over the years, load balancers have matured from simple network traffic distribution systems to next-generation Application Delivery Controllers (ADCs). This essentially means that in addition to providing Layer 4 load balancing, ADCs can manage Layer 7 for content switching, SSL offloading and advanced features such as content redirection and server health monitoring.

Thus, load balancers don’t just balance traffic; they also play a major role in enhancing application performance. The same goes for APIs. By allowing incoming requests to be distributed across multiple servers, load balancers improve API reliability and scalability and enable them to handle more requests.

From addressing business needs to handling housekeeping, applications and APIs are the numerous cogs in a business' giant wheel that keep it running smoothly. When it comes to managing the traffic directed towards them, one must remember that it need not be just North-South traffic. With an average usability of around 15,000 APIs per organization, we must be cognizant that conversations between internal APIs can also clog bandwidth.

How can load balancers help?

Why Load Balance for Applications and APIs?

• Load balancers improve performance and response times

Servers can fail, undergo maintenance and downtime and give delayed responses—this is the reality of a network. Even with all guard rails in place, such situations can eventually result in severe application outages. Load balancers are sensitive to such failures and automatically redirect traffic to the backup server, making the entire application ecosystem more resilient and stronger with zero disruption to application access.

• They enhance scalability and resource utilization

As demand grows, additional servers are added to the system. With the help of load balancers, traffic can even be distributed between these servers, allowing applications to scale and cater to thousands of client requests. Similarly, load balancers confirm if the resources within the ecosystem are catered to in a manner that is fair and balances out the chaos in the network.

• Increased reliability and fault tolerance

Since traffic is redistributed across servers, applications are highly available. Even if one or more servers are down, requests are distributed to an available server, increasing fault tolerance and reducing response time latency.

Load Balancing Strategies

While the theory behind load balancers seems simple enough, the practical implementation requires forethought and strategy—from technique to algorithms, hardware, server load and the general traffic that the network attracts. For instance, load balancers can make decisions based on the network protocol, the type of data that is being sent and the nature of the application. Additionally, they must support encryption protocols and utilize the right kind and mix of algorithms, from Round Robin to least connected to chained failover and weighted response time. Load balancing strategies involve using the right algorithms.

Load Balancing Algorithms

Load balancers typically use the following algorithms:

• Least Connection
• Round Robin
• Weighted Least Connection
• Weighted Round Robin
• DNS Round Robin
• IP Hash
• Resource-based
• Weighted Response Time
• URL Hash

Resource Based (Adaptive) Load Balancing Method

Resource-based (or adaptive) load balancing makes decisions based on status indicators retrieved by the load balancer from the back-end servers. Based on the status indicator, the load balancers set the dynamic weight of the server appropriately.

In this fashion, the load balancing method is essentially performing a detailed “health check” on the real server. This technique is applicable to situations where load-balancing decisions are made based on a server's health information. For example, this method would be useful for any application where the workload is varied and detailed application performance and status are required to assess server health. This method can also be used to provide application-aware health checking for Layer 4 (UDP) services via the load balancing method.

Source IP Hash Load Balancing Method

The source IP hash load balancing algorithm uses the client request's source and destination IP addresses to generate a unique hash key, which is used to allocate the client to a particular server. As the key can be regenerated if the session is broken, the client request is directed to the same server it was using previously. This method is most appropriate when it’s vital that a client consistently returns to the same server for each successive connection.

What Impact Does a Load Balancer Have on Application and API Performance?

Load balancers distribute traffic to multiple servers so that applications are highly available. However, what boosts application performance is that load balancers for applications and APIs also act as ADCs. Additional features such as content caching, data compression and Layer 7 switching enhance application functioning.

• Content caching is a concept where frequently used data is stored on the load balancer to be reused again. This prevents frequent trips to the server for data retrieval, resulting in better application performance.
• Data compression is another technique to reduce the amount of data (read traffic) by compressing it at the load balancer level. This significantly decongests the pathways to the servers by sending smaller data packets across the network.
• Layer 7 switching uses application-layer criteria to determine where to send a request. This provides an application delivery controller with much more granular control over forwarding decisions.

Load balancers use the same technique to enhance the performance of APIs, too. Client requests need not be aimed at applications alone, they could also potentially demand services of APIs (internal or external). The request could be from within the network or even externally. In this scenario, a load balancer then acts like an API gateway to distribute the request to the right endpoint. API service requests can be optimized by load balancers by setting up the right parameters such as timeouts, retries, health checks, caching and compression. Load balancing API requests can lead to better user experiences because it inherently increases the responsiveness of the service, portrays a picture of reliability and consistency and enables users to experience the right features at the right time.

Using a Load Balancer for Boosting Application Performance – The Vantage Point

SkyVantage is a provider of hosted airline reservation services that provides an industry-leading airline reservation and management system for specialized small-to-medium and start-up airlines, as well as airline charter organizations. The SkyVantage Airline Management System (SVAMS) includes a comprehensive set of real-time modules such as management of passenger reservations, check-in counter and dispatch, advanced reporting and gate and flight operations.

Initially, SkyVantage experienced explosive growth – doubling in size every quarter. As the company grew, the hosting system infrastructure began to show signs of fatigue. The application servers were not adequately managing the web traffic, and user experiences were noticed to be inadequate. In addition, deficiencies in the technology terminated connections such as splitting packets, which increased the bottlenecks.

SkyVantage began using Progress Kemp LoadMaster, which enabled high availability and Layer 7 content switching. Using a Layer 7 load balancer allowed SkyVantage to check and adjust settings amongst its servers accordingly. Continuous monitoring helped them determine the servers' efficiency. It also used SSL acceleration to keep the data encrypted and secure. With 99.999% high availability and stateful failover, LoadMaster allows SkyVantage to provide a reliable hosted management system to its customers.

Additionally, the easy-to-use web interface included with the management of the LoadMaster appliances allowed SkyVantage to manage its servers—removing and adding servers as needed—without affecting end-users. A more streamlined management approach also means minimal support issues.

In the highly competitive and time-crunched airline industry, fast response time is essential and any downtime can be detrimental to any web-facing business. With LoadMaster, millions of dollars in airline bookings are processed more seamlessly every day through the SkyVantage Airline Management System. Every customer web click is processed and managed smoothly through the LoadMaster load balancers.

How Do You Select a Load Balancer for Applications and APIs?

When choosing a load balancer, especially when you have numerous applications and APIs to cater to, organizations need to keep the following strategies in mind:

1. What are the business goals for your applications and APIs?
   The choice of load balancer for your business ultimately depends on your business requirements from those applications and how they behave. Ultimately, load balancing solutions must enable organizations to scale their operations and be cost-effective, all the while maintaining high availability and exceptional user experience.

2. What features and capabilities do you require from a load balancing solution?
   To understand what you need from a load balancer, you need to have a good grip on your network, application and API behavior. You might want to choose between a hardware or software load balancer. You might want to look for advanced features that can cater to operations that range from Layer 3 to Layer 7. You might also want to check if the load balancer provides capabilities that can offer high availability and scalability such as stateful connection failovers, session persistence, clustering and disaster recovery.

3. Does your load balancing choice cater to cloud-native strategies and container orchestration?
   Since most organizations are hosting their applications on the cloud, a very important question to ask is: Does my load balancer extend the features and capabilities of an ADC to the cloud? In short, is it designed and optimized for the cloud? Although most cloud providers provide in-house load balancing options, a cloud-native load balancer such as LoadMaster provides capabilities that are more powerful and cheaper than native offerings.

4. What licensing option would you prefer?
   Once you have decided on the features, it will be time to consider the licensing options. Would you prefer to go for a perpetual, pooled or metered license? What kind of arrangement suits you the best in terms of the number of applications and their back-end servers that you need to support? Financial decisions like these can be based on the value that you derive from the price that you pay for the licenses.

Securing Applications and APIs With a Load Balancer

While other capabilities are important, when choosing a load balancer, ensuring that they also help keep your applications and APIs secure is essential. For instance, LoadMaster helps provide a cost-effective solution to provide additional layers of security to your applications to maintain the integrity and availability of services and improve the application experience. For example, LoadMaster has a feature called Web Application Firewall (WAF) that provides protection against exploits without having to make any changes to the application. The WAF feature helps to protect applications from common vulnerabilities such as SQL injection and cross-site scripting. In fact, it even lets you create per-application security profiles to enforce source location-level filtering, adopt pre-integrated rulesets for common attack vectors and custom security rules support.

Additional features such as pre-authentication and SSO enhance security by authenticating and authorizing users at the network perimeter even before accessing the application. By integrating Identity Access Management (IAM), intelligent policy applications and traffic steering, load balancers enable strong controls for critical workloads and services. Many load balancers enable SSL encryption, allowing SSL offloading at the load balancer level.

Future Trends and Predictions

Projections suggest that the load balancer market reach a value of USD 5.18 billion in 2023 to USD 16.07 billion by 2032, representing a compound annual growth rate (CAGR) of 15.20% over the forecast period. Cloud adoption and innovations in technology are creating new requirements for load balancers. They are poised to take advantage of advanced machine learning algorithms to utilize real-time traffic to adapt to changes in the real-time demand for services. Load balancers are also evolving to adapt to the hugely popular Kubernetes container orchestration systems, which help maintain service delivery.

Businesses are now taking a modern approach to adopting load balancers—preferring load balancers with enhanced security features, support for Kubernetes Ingress, providing load balancing at all layers from Layer 4 to Layer 7, support for high-performance applications and cloud-native and cloud-hosted applications in a multi-cloud environment.

Load balancers have evolved over the decades. From merely rerouting traffic, they have adapted to the changing technological environment with ease. Load balancers are critical components in the IT ecosystem that enhance API and application performance. They also enhance scalability and resource utilization, providing increased reliability and fault tolerance.

While choosing a load balancer, double-check to see if it aligns with your application and API business goals. The features and capabilities in your chosen load balancer must help optimize application and API performance.

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