Building a Tunnel through NAT Using OpenFlow

This paper presents a stateful algorithm based on OpenFlow protocol to establish a tunnel without the requirement of global IP address in a simple and scalable manner. The algorithm modifies incoming packet according to a database of four tuples mapping relationship, which controller maintains, then forwards modified packet based on kernel routing table through established tunnel, and finally reconstructs received packet and transfers to the original destination. The experiment shows proposed algorithm can effectively improve utilization of network link resources.