Network Load Balancers

Network load balancers distribute interactive traffic across a number of hosts by using dynamically updated rules for load balancing while providing a single system image to the client system. Network load balancing is an important part of network management because of the amount of data transmitted across local area networks (LAN) and wide area networks (LAN). Network load balancers include hardware devices, software applications, or packages that include both. A network load balancer can be used to support high-traffic Web sites, data center serves, and database hosting servers. In Web load testing, network administrators use a Web server balancer to cycle each server request through a domain name system (DNS) address series. This approach works for most standard Web site rollouts, but may be insufficient for very high volume sites such as e-commerce web sites.

Network load balancers can be used to overcome service bottlenecks by swapping hubs with switches and adding network interface cards. In this way, a network load balancer can effectively subnet the network. Often, the high costs of subnets drive organizations to implement an Internet load balancer. In this case, load balancing uses the border gateway protocol (BGP). The BGP4 standard developed by the Internet Engineering Task Force facilitates the use of network load balancers to scan many thousands of addresses all relating back to a backbone address. This technology is called classless inter-domain routing.

Cluster servers are another configuration for network load balancers. Clustering involves combining computers, redundant connections, and high-capacity storage devices into what looks like a single system. Server load testing is performed by filtering requests to a management server that determines which cluster server is most readily able to handle each request. The request is then routed to the appropriate server. Other functions for network load balancers include state monitoring, path testing, packet inspection, application routing, Web filtering, and throttling.