video. In order to dynamically treat these massive amounts of traffic, traffic flows are prioritized in real time by type of content and often by application as well. For example, e-mail usually has a lower priority than real time streaming video because short delays on e-mail and text messages aren't noticeable. The software control in SDN is able to manage these peaks and prioritize particular types of traffic. Software Defined Networks have a centralized controller that specifies the treatment of applications www.TechnicalPDF.com and handling of traffic. This is accomplished via policies sent to network nodes in real time, directing the use of particular routes, and priorities for traffic flows. These policies are transmitted on the control plane. The controller sends out policies in real time to network nodes (switches and routers) that transmit the actual data. For example, if a route is out of service, the controller will transmit updated policies to nodes SO that all traffic is rerouted to a functioning path in the network. The following are examples of control plane policies: Redirecting traffic during peaks. Opening bandwidth when it is needed during an event such as a presidential inauguration. For example, carriers commonly rate-limit traffic by running a 400Gbps pipe at 10Gbps. When required, the bandwidth can be easily increased to 400Gbps. Reconfiguring an optical multiplexer on the fly, automatically, or manually, via remotely entered computer commands. Selling web portal access to IT managers SO that they can add more bandwidth for a special event without waiting for the carrier to provision more service. Decreasing delays and increasing revenue from new services more quickly by speeding up installations such as cable modems and high- speed network access for commercial customers. This means that an installer can make one visit to an enterprise to install gear, and then power up the service remotely through software. Previously, multiple onsite trips were required for setup. Virtual Networks and F