VDE is a virtual network that can be spawned over a set of physical
computers over the Internet.

VDE connects together: (1) real GNU-linux boxes (tuntap) (2) virtual
machines: UML-User Mode Linux, qemu, bochs, MPS.

VDE can be used:
  - to create a general purpose tunnel (every protocol that runs on
    Ethernet can be put into the tunnel)
  - to connect a set of virtual machine to the Internet with no need of
    free access of tuntap
  - to support mobility: a VDE can stay interconnected despite of the
    change of virtual cables, i.e. the change of IP addresses and
    interface in the real world