he availability of the network by making it readily available 24 *7. The controller should also define Quality of Service functionalities on a flow-to-flow basis. Downloaded 4/15/2022 9:44:49 AM Nova Southeastern University IP Address: 137.52.76.29 The Heart and Brain of SDN Network Programmability The basis on which SDN concept was developed is Network programmability. In previous days, network was configured from device to device. This manual approach was time consuming and was predicted to errors. The conditional changes don't affect the config in any way because the system is static. "All Hail" the controller as it gives an interface to the system in form of a UI sort of environment. What does it mean by programmable interface? The controller actually redirects traffic. Example is building a shielded network that makes the traffic inbound to the server. Now if the sources trying to fetch the network are clean then the firewall should not consume all the resources and the IT firm should make sure that traffic should not go through this shield and should be outsourced or rather outbound. It is monotonous when it comes the old style networks. Few other areas of concern are that organisations must look for generally include masking of packets when the arrive at the controller. But the job of controller is not easy at all as it must mask tedious combinations of multiple packet header fields. Dynamic deployment of these filters should be opted for on VMs and being the intermediaries' i.e. the controllers they must forward the table entries to the switch. Who wants static programming of network? No one right? So the controller allows for short slate like temporary plates to configure that enables scripting Command Line Interfaces to be renewed. To mention another fact that how does controller enables such tremendous programming capabilities is by implementation of the upper layer's Application Programming Interfaces. (Ashton and Metzler, 2012). This upper layer or "Northbound" Application Interface has a small trick