Network Virtualization and Network Hypervisors

Modern communication networks have to deal with dynamically changing requirements of emerging applications. In order to support such heterogeneous requirements on the same substrate network, concepts for network abstraction and network programmability are essential to offer applications that individually tailored views on the network. Network virtualization is the basic concept to provide an abstraction of a substrate network that can be offered to a network application provider. Here, a network hypervisor realizes the level of indirection between substrate network and virtual network(s). Additional programmability can be offered through the concept of Software‐Defined Networking (SDN). SDN provides a network abstraction based on a centralized view on a network to program individual features such as forwarding rules inside a network. This chapter gives an overview of the networking concept of network virtualization as the example of the virtualization of SDN‐based networks. The combination of network virtualization and Software‐Defined Networking provides full network abstraction and adaptability. We detail the basic features of a network hypervisor, abstraction and isolation, and provide the example of FlowVisor as a prominent network hypervisor example in the state of the art.