Application delivery controller
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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 outer firewall or router and a web farm.
A common misconception is that an ADC is an advanced load-balancer. This is not an adequate description. In fact, an ADC includes many OSI layer 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, starting around 2004, offered simple application acceleration and load balancing. In 2006, ADCs began to mature when they began featuring advanced applications services such as compression, caching, 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.
Application acceleration products were available from many companies by 2007, for example F5 Networks, Juniper Networks, Microsoft, KEMP Technologies and aiScaler. 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.
In 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, aiScaler and A10 Networks who became industry leaders.
In 2015, Brocade Communications Systems acquired the SteelApp business unit of Riverbed Technologies, Inc. to expand on its ADC offerings and consolidate its position in the Software Defined Data Center/Software Defined Network arena. Brocade renamed SteelApp to Brocade Virtual Traffic Manager (aka VTM).
In 2016, Webscale launched their Cloud-based Application Delivery Platform, with the included software-defined ADC to integrate seamlessly with the application and utilize cloud infrastructure to improve performance, availability and security 
In 2017, Open Source ADC Zevenet is launched with a high platform integration as it's available for virtual, bare metal, hardware and public or private cloud focused in the innovation of high performance, availability and security of services, applications, networks and data centers. 
- Ann Bednarz (July 3, 2007). "Gear makers bundle network optimization features". Network World. Retrieved May 26, 2013.
- Jeffrey Burt (September 20, 2012). "Cisco Ending ADC Business, Ceding Market to F5, Citrix, Riverbed –". eweek.com. Retrieved June 27, 2013.
- Sean Michael Kerner (May 1, 2008). "Applications And Networks Need to Unite". InternetNews.com. Archived from the original on May 5, 2008. Retrieved May 26, 2013.
- Paula Musich (April 3, 2006). "Application Acceleration Market Hits $1.2B". eWeek. Retrieved May 26, 2013.
- "Brocade acquires Riverbed ADC to bolster virtual delivery services".
- "APPLICATION DELIVERY CONTROLLERS".
- "CLOUD ADC".
- "Open Source ADC".