Application delivery controller

An application delivery controller (ADC) is a computer network device in a datacenter, often part of an application delivery network (ADN), that helps perform common tasks such as those done by web sites to remove load from the web servers themselves. Many also provide load balancing. ADCs are often placed in the DMZ, between the firewall or router and a web farm.

Features

A common mis-conception is that an ADC is an advanced load-balancer. This is not an adequate description. In fact, an ADC includes many OSI layers 3-7 services including load-balancing. Other features commonly found in most ADCs include SSL offload, Web Application Firewall, NAT64, DNS64, and proxy/reverse proxy to name a few. ADC & ADN are marketing terms invented by F5 Networks and other vendors to imply that business applications require front end intelligence to supplement and enhance application flows from client to server back to client. First generation ADCs, about 2004, offered simple application acceleration and load balancing.

In 2006, ADCs began to mature when they began featuring advanced applications services such as compression, cache, connection multiplexing, traffic shaping, application layer security, SSL offload and content switching combined with services like server load balancing in an integrated services framework that optimized and secured business critical application flows. Some also offered features such as content manipulation, user access control, DDoS protection, advanced routing strategies and server health monitoring.

Availability

Application acceleration products were available from many companies by 2007, for example F5 Networks, aiScaler, Juniper Networks, Microsoft, KEMP Technologies and Strangeloop Networks. Cisco Systems offered application delivery controllers, until leaving the market in 2012. Market leaders like F5 Networks and Citrix had been gaining market share from Cisco in previous years.

The ADC market segment became fragmented into two general areas: 1) general network optimization and 2) application/framework specific optimization. Both types of devices improve performance, but the latter is usually more aware of optimization strategies that work best with a particular application framework, focusing on ASP.NET or AJAX applications, for example.

For 2005, a market research firm estimated the ADC market at US$ 727 million, with major vendors including F5 Networks and Cisco Systems. In 2012, Cisco Systems lost market share to companies like F5, Citrix, Radware and A10 Networks who became industry leaders.