What is a load balancer?




What a load balancer does is exactly what it sounds like, distributes server load in an efficient manner. It serves as an intermediary between the user and the cluster of servers, coordinating the user’s requests across all the servers that can accommodate those requests, whether those servers are local or located across the internet or private networks.




In this section, we will explain what a load balancer is and the types of load balancers,





As early as 1990, load balancing was introduced by using hardware to distribute traffic among networks. As Application Delivery Controllers (ADCs) were developed, they made load balancing more secure, allowing applications to be accessed uninterrupted even during peak times.




Let us have a look at the basic diagram that shows how LB works.







Typically, a load balancer is a piece of hardware (physical or virtual) that functions as a reverse proxy in order to distribute network traffic and application traffic between multiple servers. By using a load balancer, users can access applications more concurrently and improve overall application reliability.



By balancing load across multiple servers, anyone cannot become overloaded and possibly experience failure. Additionally, load balancing helps prevent downtime by improving service availability. In order to meet an organization’s application requirements, load balancing determines the server that is most suitable for processing requests efficiently. As a result, users can expect a better experience.



Additionally, the load balancer manages information flow between server and endpoint device by aiding servers in moving data efficiently. Load balancer also tests the health of the request-handling servers, and if necessary, a server that is unavailable is removed until it is available again.




In order to address the specific network issues, several load balancing techniques exist:





1. Network Load Balancer / Layer 4 (L4) Load Balancer




With IP addresses and destination ports as network variables, Network Load Balancing is distributing traffic at the transport layer by deciding which routes to take. This type of load balancing is TCP (level 4) and ignores any parameters related to the application, such as type of content, cookie information, header information, locations, and behavior of the application. As NAT is performed without inspecting packet content, NLB only pays attention to the network layer information and routes traffic accordingly.





2. Application Load Balancer / Layer 7 (L7) Load Balancer




As the highest layer in the OSI model, Layer 7 load balancers distribute requests according to multiple application-level parameters. L7 load balancer evaluates a wide range of data, such as HTTP headers and SSL sessions, to determine how to distribute server load based on several factors. This is how application load balancers control the traffic to the servers based on individual usages and behaviors.





3. Global Server Load Balancer/Multi-site Load Balancer




Cloud data centers are increasingly hosting applications, with locations around the world, enabling the global server load balancer to extend the capabilities of general L4 and L7 across several data centers, allowing the efficient distribution of global traffic, with minimal impact on end-users. In addition to enabling efficient traffic distribution, a multi-site load balancer can also offer quick recovery and smooth business continuity.





Each type of load balancer receives balancing requests, which are handled according to a predefined algorithm. Our discussion here is limited to the industry standard algorithms





1. Round Robin Algorithm




The round-robin method of load balancing distributes requests among several servers. For each client request, each server receives it. The algorithm instructs the load balancer to go back to the top of the list and repeats again.




2. Weighted Round Robin Algorithm




Site administrators can assign weights to each server through the weighted round-robin algorithm according to factors such as traffic handling capacity. The weighted servers receive a greater share of client requests.





3. Least Connections Algorithm




According to this algorithm, traffic is routed to the server with the lowest traffic level. As a result, performance is maintained, particularly at peak times by maintaining a uniform load across all servers.





4. Least Response Time Algorithm




In a manner similar to the least connections method, the least response time allocates requests based on server connections as well as the shortest response time, reducing load through two layers of balancing.





5. IP Hash Algorithm




For optimal performance, the IP address of the client is assigned to a fixed server.







That’s it!







It is our hope that this article provided you with more information.






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