I believe anyone who did a fair amount of network development in the kernel sooner or later arrives at the idea of a virtual networking framework with switches, hubs and configurable links in between. Half of those will make an attempt to implement it, because it is a fun project, but only few will move beyond tinkering to having something functional. However getting something like this into a shippable production state is a genuinely remarkable achievement :)

Mininet is a virtual test bed designed for running software defined network experiments via OpenFlow controllers. GENI on the other hand, aims to be a physical test bed spanning the nation connected to a separate backbone for researchers to run their SDN experiments [1].

[1] http://www.geni.net/

It resembles this project: http://www.netkit.org/

This sounds very interesting, does anyone mind explaining the differences between it and VDE though (I'm betting I'm missing how this solution works or its purpose)?

does it do the same thing as this: http://www.nrl.navy.mil/itd/ncs/products/core