consists of many geographically distributed areas, that is, PoPs or central offices. Virtualizing the core network facilities such as EPC or IP multimedia subsystem (IMS) can increase the capacity of a mobile core network dynamically. 6) Virtualization of mobile base stations: In recent years, the virtual- ization of radio access network has been proposed and drawn sig- nificant attention. After virtualizing base stations, multiple service providers can share the same physical resource SO that the coverage and resource utilization are both increased. 7) Virtualization of home environment: The residential gateway or home gateway is another place where traditional network services are deployed as dedicated hardware. When upgrading the home gateway, often a new hardware needs to be shipped together with 3 Network Function Virtualization manual installation. Debugging is challenging as the end users do not have the expertise and knowledge to perform troubleshooting. Typical network services in a home environment include parental control, DPI, firewall, and SO on. With NFV, the gateway can simply be a forwarding device while other complex functions can be run in the providers' data center. This can help reduce the operational overhead and ease the management tasks. 8) Virtualization of CDN: Content delivery network (CDN) hosts massive amount of objects, ranging from web to video, in a distributed manner. The demand of the CDN storage can increase drastically with the content's popularity, such as flash crowd. A popular program's live streaming can put large pressure on both the CDN and the network. Today, CDNs are more and more tightly integrated with the service provider's network given the latter's wide geographic distribution and service-level agreement (SLA) provided. Virtualizing the CDN nodes and deploy them in the cloud can provide resource elasticity as demand changes. 9) Fixed access network functions virtualization: The main fixed line access network technologies today are based on digital subscriber line (D