flexibility of network service provisioning and reduce the time to market of new services. By leveraging virtualization technologies and commercial off-the-shelf programmable hardware, such as general-purpose servers, storage, and switches, NFV decouples the software implementation of network functions from the underlying hardware. As an emerging technology, NFV brings several challenges to network operators, such as the guarantee of network performance for virtual appliances, their dynamic instantiation and migration, and their efficient placement. This chapter presents brief overview of NFV, explain its requirements and architectural framework, present several use cases, and discuss the challenges and future directions in this burgeoning research area. The third chapter discuss about open flow protocol. The SDN controller is interfaced with the hardware of the network i.e., with switches and routers using OpenFlow. Basically, OpenFlow is an open interface used for configuring the forwarding tables of network switch according to the desired path derived by the SDN controller. OpenFlow enables more innovation in controller platforms, applications and describes a solution for each frame or packet flow. OpenFlow is based on an Ethernet switch, with an internal flow-table, and a standardized interface to add and remove flow entries of forwarding table of the system. The control mechanism from each one of the switch and router up to SDN controller are encrypted with the Transport Layer Security (TLS) and Secure Socket Layer (SSL) OpenFlow protocols are used to provide the additional security inside the Network. The fourth chapter discusses about controllers of software defined networks. Designing and organizing networks has become extra innovative over the past few years with the assist of SDN (software-defined networking). The software implements network protocols that undergo years of equivalence and interoperability testing. Software-defined networking (SDN) is an move toward to computer networking that allows net