N architecture the second layer in which the decision making is done. This plane is centralized and the SDN controller lies in this plane. Data Plane: In the SDN architecture the lowest layer from which the actual data movement takes place. The SDN switches lies in this layer which uses the flow rules to forward a packet provided by the controller. Network Function Virtualization: The functions such as firewall, NAT which are provided by the middle boxes is virtualized in the form of software to be run on standard X86 server or data center. OpenFlow: It is the standard protocol for SDN given by ONF. The Open Flow specifications are used to develop open flow switches. Programmable Networks: To remove the ossification existing in the network the concept of programmable networks comes into picture in which the control logic is programmable and can be changed as per requirement. Software-Defined Networking: It is a networking paradigm based on decoupling the control plane from the data plane and putting the control plane on a centralized location (i.e., controller that provides a centralized management and control over the network). Virtual Network Functions: The virtual network functions are the NF (i.e., network functions running as a piece of software over a server). Downloaded 4/15/2022 9:44:49 AM Nova Southeastern University IP Address: 137.52.76.29 Chapter 2 Virtualizing Network Functions in Software-Defined Networks Vishal Kaushik University of Petroleum and Energy Studies, India Ajay Sharma SRM University - Haryana, India Ravi Tomar University of Petroleum and Energy Studies, India ABSTRACT Software-defined networking (SDN) is an emerging network architecture that facilitates the network administrator to control and manage network behavior dynamically. Differentfrom traditional networks, software-defined networks support dynamic and scalable computing. The dynamic behavior is achieved by decoupling or disassociating the system. The swing of control from tightly bound individual networks to assessable computin