Network functions virtualization (NFV) is a network architecture concept that proposes virtualizing network appliances used for various network functions. These functions include intrusion detection, caching, gateways, WAN accelerators, firewalls, and more. Using SR-IOV, instances are no longer required to use para-virtualized drivers or to be connected to virtual bridges within the host. Instead, the instance is attached to a Neutron port that is associated with a virtual function (VF) in the NIC, allowing the instance to access the NIC hardware directly. Configuring and implementing SR-IOV with Neutron is outside the scope of this book.