alization layer or the hypervisor: It abstracts the hardware resources and decouples the VNF software from the underlying hardware. Therefore, the software can be deployed on different physical resources. 1 A Comprehensive Study on 5G (c) Virtualization resources: It is virtual resources of computing, storage, and networking. 3. NFV management and orchestration (MANO) layer: It corresponds to the control plane and manages the physical and/or software resources for NFVI and VNFs. It includes: (a) Virtualized infrastructure manager (VIM): It performs the control operations and manages the interaction of VNF with the underlying resources such as allocation and management of infrastructure resources. Moreover, VIM guarantees the network connectivity and manages the NFVI resources, including allocation of VMs, computing, and storage resources. (b) NFV orchestrator (NFVO): It is responsible for the management of NFV infrastructure and software resources. It performs the orchestration and management of both VNFs and network services. NFVO is responsible for creating E2E services across multiple VNFs. (c) VNF managers: It manages the VNF instance life cycle including instantia- tion, update, scaling, and termination. 4. Operations support systems (OSS) and business support systems (BSS): (a) OSS is responsible for several management services involving network, fault, and configuration management. (b) BSS provides a customer product, order management, and SO on. 1.4.2.2 Research Works on NFV Various challenges have been addressed in [60] for an efficient integration of NFV within the 5G eco-system in terms of management, orchestration, resource optimization, and SO on. Table 1.6 presents recent research works addressing these challenges. An efficient implementation of NFV within the 5G eco-system is required to ensure portability, interoperability, and consistent MANO of different applications and services to be executed through a unified interface. Therefore, standardizing of a unified northbound interface for NFV is con