A few killer applications that rocked the Internet community these years are peer-to-peer (P2P) file-sharing applications
and VoIP (voice over Internet Protocol) telephony services. Unlike traditional client-and-server applications in which servers
are services provider and by default should be public addressable, each peer in P2P networks can play both roles (client and
server). However, legacy usage of the network address translation (NAT) module on most wireless access points (APs) causes
new problems with emerging P2P communications especially in opposing APs (both peers of an Internet connection are behind
AP) where each peer uses private Internet Protocol (IP) address and neither side has global visibility to each other. This
article therefore examines such issue from three approaches, 1) leveraging the complexity of client application, 2) introducing
additional intermediate gateways and protocols and 3) enhancing the wireless AP itself. Client-based solutions such as UDP/TCP
hole-punching suffer from race condition while gateway-based solutions tend to incur overhead for interoperability and deployment.
This paper proposes a scalable port forwarding (SPF) design for wireless AP, which introduces little or negligible time and
space complexity, to significantly improve the connectivity and scalability of a conventional AP by 1) lessening the race
condition of P2P traversals in opposing APs, 2) multiplexing the port numbers to exceed theoretical upper bound 65,535 and
3) allowing more servers to bind to a specific port.
Keywords Wi-Fi - Access Point (AP) - Peer-to-Peer (P2P) - Port Forwarding - Network Address Translation (NAT)