Application Delivery Controllers in an SDN World – Programming the Network?


Over the past several years, server virtualization has led to consolidation of physical server resources to reduce cost and enable flexibility by allowing applications to be virtualized and distributed.

A similar trend is underway for networks – traditional networks are now becoming more dynamic to lower cost and reduce vendor lock-in. The two key efforts of note: Software Defined Networking (SDN), which brings standardization through APIs, and Network Function Virtualization (NFV) that allows operators to quickly enable value-added services.  The NFV initiative is highly complementary to SDN.

SDN enables the management aspects of the network to be decoupled from the data flow. By centralizing the control aspects of a network, administrators are able to monitor and direct network traffic using software. NFV is a network operator initiative to increase the virtual network functions within data centers and service provider networks.

Very similar to what happened in with the virtualization in the servers, SDN and NFV are now enabling programmability and automation to support the demands of users (and applications) to which the network must respond to.  The popularity of SDN will be driven by the availability of innovative SDN applications that work with new SDN controllers and can quickly deliver the benefits for this dynamic network.

At the interface of network and applications (also called Layer 4 through Layer 7 or L4-7 for short) are devices that provide scalability, availability, visibility and management for applications. Traditionally called load balancers or application delivery controllers (ADCs), these devices are now morphing to decouple their control and data plane aspects to more seamlessly integrate with (and program) the SDN controllers as well as seamlessly orchestrate with the application environment.

Since the ADCs deploy at the intersection of the network and applications, they act as sensors to changing user demands – detecting increased user latency, lack of available application resources, availability or outage issues etc. The ADCs respond with triggering server orchestration to program the applications if the issues are related to applications.

The programmability of the network to respond to user and application demands comes from the standardized APIs (currently OpenFlow is the choice) that newer SDN controllers provide. These APIs can be used by the ADCs to gain statistical information to gauge the health of the network as well as to program the flow of data through router and switches managed by the SDN controllers

Radware has introduced SDN applications that work with SDN controllers to secure networks and provide on-demand resource scalability and steering based on application service level agreement.

Learn more about the analysis and adoption these designs and architectures: Read the 2015 Guide to SDN and NFV


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