NAT Hole Punching Revisited

Abstract—Setting up connections to hosts behind Network Address Translation (NAT) equipment has last been the subject of research debates half a decade ago when NAT technology was still immature. This paper fills this gap and provides a solid comparison of two essential TCP hole punching approaches: sequential and parallel TCP hole punching. The comparison features current conditions and thoroughly compares setup delay, implementation complexity, resource usage, and effectuality of the two approaches. The result is a list of recommendations and a portable, effectual, and open-source Java implementation. I