application delivery controller (ADC)

An application delivery controller (ADC) is a network unit used in data centers to control and optimize client connections. Usually , an ADC component is part of the Application Delivery Network( ADN). It helps the ADN network optimize traffic and can, for example, reduce the load on web servers. Many ADC controllers also support load balancing and improve network security.

The functionality of application delivery controllers spans OSI layers 3 through 7 and extends far beyond load balancing, which flexes user access to virtualized servers and applications. ADC controllers support compression, multiplexing of connections, traffic shaping, content switching, web application firewall, resource utilization, ensure high availability and support several other functions such as server health monitoring. With this information, load balancing can be better optimized because connection requests are not sent to overloaded servers.

There are different methods to monitor the state of servers. For example, with the ICMP protocol, with TCP, UDP, HTTP or SMTP.