n2n is a layer-two peer-to-peer virtual private network (VPN) which allows
users to exploit features typical of P2P applications at network instead of
application level. This means that users can gain native IP visibility
(e.g. two PCs belonging to the same n2n network can ping each other) and be
reachable with the same network IP address regardless of the network where
they currently belong. In a nutshell, as OpenVPN moved SSL from application
(e.g. used to implement the https protocol) to network protocol, n2n moves
P2P from application to network level.