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Load balancer, as the name suggests, is a device which is used for optimal distribution of network or application traffic over a number of hosts (servers). Load balancers are becoming popular with every passing day because network managers and IT administrators are facing an exponential increase in the traffic on their networks and applications. To cater this increasing traffic, multiple servers are deployed either in active/redundant mode or in active/active mode. Load balancers are used to balance the workload of each server deployed for the same application.
There are two main types of load balancers:
- Network Load Balancer (Link Balancer)
- Application Load Balancer
The main purpose of both these load balancers is same but the application is different. We shall be discussing the functionalities and advantages of both types of load balancers in detail in this article.
Network Load Balancer
A network load balancer is used to balance the traffic over multiple internet service providers (ISPs) links. This type of load balancer is sometimes referred to as link balancer. The functionality of a link balancer can be fully understood by reading the following scenario.
Suppose, a company/organization has more than 500 employees, the network administrator has procured two internet links of 15 Mbps CIR from two different internet service providers, say link A and link B. Both these links are being terminated on a router. The router is configured in such a way that link A is primary and link B is secondary. If link A goes down, the traffic is routed through link B. In this scenario, the network administrator is paying equal amount to both service providers yet the link B is under-utilized and is only used when link A is not working. The ideal solution would be to introduce a link balancer in the network and terminate the internet links on the link balancer. In that way, both link A and link B will be configured as active links and traffic will be distributed amongst them. A total of 30 Mbps throughput will be available to the end users. Link balancer can also help is optimizing the cost as the throughput of the links could be reduced which results in a lower operating expenditure.
Application Load Balancer
Similar in functionality to the link balancer, application load balancers are used to distribute the load of application traffic over a number of servers. We shall be exploring the concept of the application load balancer with a scenario as well.
The same company is running an ERP application with business critical data residing in its database. Most of the users access the data on daily basis. The application is hosted on two servers, say server A and server B. These servers are deployed in an active/standby configuration. Server A is active and server B is standby. Server B replicates and copies the data from server A on daily basis. The users are experiencing lags and delays in accessing the application. The system administrator decides to install an application load balancer and terminate the servers on the load balancer. In this way, both the servers are configured in active/active configuration and users’ experience improves exponentially. Furthermore, the replication is real time and there is no delay and loss of information.
Conclusion
Load balancers are a very useful device in the environments where there are a large number of users accessing a common application or internet link. Load balancers result in lower operating expenditures and better utilization of resources. It also helps in providing a high-available infrastructure with zero to very low downtime.
