An application delivery controller (ADC) is a network device in the datacenter that helps perform common tasks done by web sites in an effort to remove load from the web servers themselves. Many also provide load balancing. They usually sit between the firewall/router and the web farm. The ADC is in many cases described as the next generation load balancer. They tend to offer more advanced features such as content manipulation, advanced routing strategies as well as highly configurable server health monitoring.

ADCs reside in the data center, typically ahead of frontline Web servers. They're deployed asymmetrically (only at the data center end) and are designed to improve the availability, performance and security of Web-based or IP-based applications. ADCs enhance the performance of Web-based and related applications for end users by providing a suite of services at the network and application layers. These services may include:

• Layer 4 through Layer 7 redirection and load balancing and failover
• TCP connection multiplexing
• Server offload (for example, SSL termination and TCP connection management)
• Data compression
• Network-address translation
• Network-level security functions, distributed denial-of-service protection and server cloaking
• Compression
• Caching