An application delivery controller is a device that is typically placed in a data center between the firewall and one or more application servers (an area known as the DMZ). First-generation application delivery controllers primarily performed application acceleration and handled load balancing between servers.
The latest generation of application delivery controllers, such as the F5 BIG-IP® product family, handles a much wider variety of functions, including rate shaping and SSL offloading, as well as serving as a Web application firewall.
A series of F5 devices, often located in widespread data centers within the same enterprise, is capable of working in concert by sharing a common operating system and control language. This holistic approach is termed application delivery networking.