ually within one operator's infrastructure domain. These functional blocks help stan- dardize the functions of virtual networking to increase interoperability of software-defined net- working elements (13, n.d.). Enterprise utilization of a VIM allows organizations to have an open, flexible, and modular architecture that serves the business purposes of scaling to meet the explosive demand at lower cost, while increasing the speed of feature delivery and providing much greater agility. With a VIM, pro- viders can rapidly make changes to the platform and extend real-time management of the service to the customer through digital portals, such as dedicated Internet on-demand bandwidth adjustments. This is made possible by the practice of virtualization. Building the Network of the Future 4.2.4.1 Virtualization In computing, virtualization refers to the act of creating a virtual (rather than actual) version of something, including virtual computer hardware platforms, operating systems, storage devices, and computer network resources n.d.). Virtualization limits costs by reducing the need for physical hardware components and improves operational efficiency. Virtualizing the infrastructure provides more efficient use of hardware, which in turn, lowers the magnitude of hardware, the related maintenance costs, and reduces power and cooling demand. Virtualizing the infrastructure is also a pivotal step in the creation of VNFs and building applications that are fault-tolerant and resilient-two topics that are covered in greater detail further in this chapter. 4.2.4.2 Virtual Machine One of the most well-known applications of virtualization is when a VM is used in hardware- assisted virtualization. A VM is an emulation of a given computer system. VMs operate based on the computer architecture and functions of a real or hypothetical computer, and their implementa- tions may involve specialized hardware, software, or a combination (17, n.d.). Also, the VM hides the server resources from the end users, including the number and 