VDE is a virtual network that can be spawned over a set of physical
computer 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:
(i) to create a general purpose tunnel (every protocol that runs
on a Ethernet can be put into the tunnel)
(ii) to connect a set of virtual machine to the Internet with no
need of free access of tuntap
(iii) 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