te Networking vTE (Core, Optical) Fabric vPGW (Mobile Gateway) (CLOS) VIMS (Voice) vSecurity (DDOS, DPI) Wireline Access (GPON, DSL) Homes, Businesses, Cell Sites, etc. FIGURE 2.3 Transformation to network cloud. Transforming a Modern Telecom Network-From All-IP to Network Cloud 2.5.1 NETWORK FUNCTIONS VIRTUALIZATION (NFV) Network functions virtualization (NFV) draws equally from information technology (IT) and net- work. Over the past decade, IT environments have gone through multiple stages of evolution, with the most recent being the use of virtualization that allows multiple software environments to share the same compute and storage hardware. The network aspect comes about when this same tech- nique is applied to functionality used in networking. In the past, networking functionality was creating using purpose-built equipment that contained the hardware and software bundled together to meet the customer's specifications. Examples include switches/routers (OSI layers 2 and 3), firewalls, session border controllers (used for voice and media networking), and mobility management entities (MME, used for signaling in mobile networks). Depending on the equipment, the hardware ranged from being a basic server, a server with special cards, or a custom-designed element using proprietary application-specific integration circuits (ASICs). In most cases, the underlying hardware can be separated from the operating software through an abstraction layer and the hardware platform deployed could be COTS hardware, which has very low unit cost because of widespread use across many industries. However, networking does have a requirement for special purpose hard- ware, either for specific physical interfaces such as optical or radio, or for throughput reasons (exceeding 10 Gb/s). In these, functional separation can be used to minimize the use of special- ized hardware. NFV leverages the IT environment, specifically the cloud paradigm, separating network soft- ware from hardware and leveraging the fact that today's modern servers 