functionality for one or several VNFs. NFV elements are the discrete hardware and software requirements that are managed in an NFV installation to provide new communication services and appli- cation services on commodity-based hardware. NFV services are deployed on commer- cial off-the-shelf hardware platform, typically run on x86-based or ARM-based computing platform and standard switching hardware. The early model of NFV, ETSI MANO, is a common reference architecture. The NFV architecture developed by ETSI 20 Chapter 1 MANO includes EMSs, which describe how individual VNFs are managed on a com- modity hardware platform. NFVI represents the entire hardware and software components which create the environ- ment in which VNFs are deployed, managed, and executed. The NFVI can span across several locations, that is, places where NFVI-PoPs are operated. The network providing connectivity between these locations is regarded as part of the NFVI. Virtualization layer abstracts the hardware resources and decouples the VNF software from the underlying hardware, thus ensuring a hardware independent life cycle for the VNFs. The virtualization layer is responsible for abstracting and logically partitioning physical resources; enabling the software that implements the VNF to use the underly- ing virtualized infrastructure; and providing virtualized resources to the VNF. The vir- tualization layer ensures VNFs are decoupled from hardware resources, thus the software can be deployed on different physical hardware resources. Typically, this type of functionality is provided for computing and storage resources in the form of hypervi- sors and VMs. A VNF can be deployed in one or several VMs. VIM(s) comprises the functionalities that are used to control and manage the interaction of a VNF with computing, storage, and network resources under its authority as well as their virtualization. NFVO is in charge of the orchestration and management of NFVI and software resources and realizing network services on NFVI. VNF manager(s) is re