Application delivery network

An application delivery network (ADN) is a suite of technologies that, when deployed together, provide application availability, security, visibility, and acceleration. Gartner defines application delivery networking as the combination of WAN optimization controllers (WOCs) and application delivery controllers (ADCs). At the data center end of an ADN is the application delivery controller, an advanced traffic management device that is often also referred to as a web switch, content switch, or multilayer switch, the purpose of which is to distribute traffic among a number of servers or geographically dislocated sites based on application specific criteria. In the branch office portion of an ADN is the WAN optimization controller, which works to reduce the number of bits that flow over the network using caching and compression, and shapes TCP traffic using prioritization and other optimization techniques. Some WOC components are installed on PCs or mobile clients, and there is typically a portion of the WOC installed in the data center. Application delivery networks are also offered by some CDN vendors.

The ADC, one component of an ADN, evolved from layer 4-7 switches in the late 1990s when it became apparent that traditional load balancing techniques were not robust enough to handle the increasingly complex mix of application traffic being delivered over a wider variety of network connectivity options.

The Internet was designed according to the end-to-end principle. This principle keeps the core network relatively simple and moves the intelligence as much as possible to the network end-points: the hosts and clients. An Application Delivery Network (ADN) enhances the delivery of applications across the Internet by employing a number of optimization techniques. Many of these techniques are based on established best-practices employed to efficiently route traffic at the network layer including redundancy and load balancing

In theory, an Application Delivery Network (ADN) is closely related to a content delivery network. The difference between the two delivery networks lies in the intelligence of the ADN to understand and optimize applications, usually referred to as application fluency. Application Fluent Network (AFN) is based upon the concept of Application Fluency to refer to WAN optimization techniques applied at Layer Four to Layer Seven of the OSI model for networks. Application Fluency implies that the network is fluent or intelligent in understanding and being able to optimize delivery of each application. Application Fluent Network is an addition of SDN capabilities. The acronym 'AFN' is used by Alcatel-Lucent Enterprise to refer to an Application Fluent Network .

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