instantiated in various locations in the network as required, without the need for installation of new equipment. In other words, Network Function Virtualisation promotes the implementation of network functions in software that can run on a range of standard IT hardware in data centres and can be managed (e.g. moved, or replicated) without the need of modifying the physical infrastructure.Figure 1: Vision for Network Functions Virtualisation (Source: ETSI)2.Network Function Virtualisation(NFV) and Software Defined Networks (SDN): Relationship between NFV & SDN: When discussing software-based networking, there is often confusion between NFV and SDN, leading to erroneous swapping of the two terms. In fact, NFV and SDN are two closely related, independent, yet complementaryand mutually beneficial technologies. As shown in Figure 2, Network Functions Virtualisation is highly complementary to Software Defined Networking (SDN), but not dependent on it (or vice-versa). Network functions can be virtualized and deployed without SDN technologies, and non-virtualized functions can be controlled by SDN. The primary distinction between the two has to do with the domain to which they apply: While NFV replaces proprietary hardware network elements (NEs) with software running on standard servers, SDN deals with the replacement of standardized networking protocols with centralized control.