Network virtualization is a particular abstraction of the physical networking infrastructure that provides support for multiple logical (virtual) network infrastructures (for example, set of switches, routes, and links) on top of a common physical (real) infrastructure.
The analogy of network virtualization is depicted in the following diagram:
The analogy of computer virtualization and network virtualization
On the left side of this diagram we can see a conventional computer virtualization, which is the virtual machine environment. In this environment the physical processor (CPU), memory, and input/output are abstracted by a hypervisor, on top of which a virtual machine can be run. This hypervisor essentially ensures the isolation of access to underlying resources and resource management. Similarly, a physical network can also be virtualized. On the right side of the preceding diagram, the network virtualization layer shown is responsible for providing an isolated view...