Measurements on the Feasibility of TCP NAT Traversal in Cellular Networks

This paper studies various techniques to overcome the barriers that firewalls and NATs cause to peer-to-peer connectivity. In the mobile context firewalls and NATs are typically managed by the mobile operator and are thus beyond the control of the mobile user. Therefore the focus of this paper is on techniques that take advantage of known behaviors of NATs and firewalls. Instead of studying how to apply explicit control to these devices we analyze how the different NAT and firewall traversal techniques would work in different cellular networks. To get an idea of operator NAT/firewall behavior we measured six cellular networks in different parts of the world. The analysis of the results shows that there is much variance in these networks; three to four (depending on the used approach) of the networks seem to allow TCP traffic between peers behind NATs or firewalls.