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Anapplication delivery controller (ADC) is acomputer network device in adatacenter, often part of anapplication delivery network (ADN), that helps perform common tasks, such as those done byweb accelerators to remove load from theweb servers themselves. Many also provideload balancing. ADCs are often placed in theDMZ, between the outerfirewall or router and aweb farm.[citation needed]
An Application Delivery Controller (ADC) is a type of server that provides a variety of services designed to optimize the distribution of load being handled by backend content servers. An ADC directs web request traffic to optimal data sources in order to remove unnecessary load from web servers. To accomplish this, an ADC includes many OSI layer 3-7 services, including load-balancing.
ADCs are intended to be deployed within the DMZ of a computer server cluster hosting web applications and/or services. In this sense, an ADC can be envisioned as a drop-in load balancer replacement. But that is where the similarities end. When an ADC receives a web request from an external host, it enacts the following process (assuming all features exist and are enabled):
Features commonly found in ADCs include:
In the context of Telco infrastructure, an ADC could provide access control services for a Gi-LAN area.
Starting around 2004, first generation ADCs offered simple application acceleration andload balancing.[citation needed]
In 2006, ADCs began to mature when they began featuring advanced applications services such ascompression,caching,connection multiplexing,traffic shaping,application layer security,SSL offload, andcontent switching, combined with services like serverload balancing in an integrated services framework that optimized and secured business critical application flows.[citation needed]
By 2007, application acceleration products were available from many companies.[1]
Until leaving the market in 2012,Cisco Systems offered application delivery controllers. Market leaders likeF5 Networks,Radware, andCitrix had been gaining market share from Cisco in previous years.[2]
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 onASP.NET orAJAX applications, for example.[3][4]