Mobile users often connect through WiFi access points and frequently find themselves behind NATs that are built into common off-the-shelf home access points. If two such mobile users want to setup a peer-to-peer connection for some application, the process involves punching appropriate holes through the NATs and can be somewhat challenging for a typical lay user. In this work we present a radically different and unique solution that uses audio-based signaling. We call our system, ANT, that utilizes Audio signaling for NAT Traversal. With ANT, unlike other NAT traversal approaches, two mobile clients can establish a direct connection with minimal user intervention and without connecting to an intermediate server. ANT uses UPnP as a standard for mapping a port on a NAT router, and getting the client’s public IP address without sending a request to an external server. NAT traversal information is then encoded using different audio frequencies and transmitted through the users’ personal phones. Upon receiving the audio through the phone, the remote mobile client decodes the sound and extracts NAT traversal configuration data. Error correction is added to enhance the reliability of ANT and eliminate the need for retransmissions. Experimental results show that a TCP connection can be established for mobile clients behind NATs with no manual configuration and minimal user intervention, even in existence of heavy noise. We believe that ANT can prove to be a simple, yet practical scheme for NAT traversal, which is as simple as dialing a phone number.

The following figure shows the ANT framework. As shown in the figure, mobile clients A and B are using laptops which are behind NATs. Both A and B have cell phones and they know each other’s phone numbers. The steps shown in the figure describe ANT’s NAT traversal technique so that A and B are able to set up a P2P connection.

A video demo of how ANT works is available. Please click the link to watch the video:http://www.youtube.com/watch?v=rUPfIi5OZ58

• Yadi Ma (yadi@cs.wisc.edu) http://pages.cs.wisc.edu/~yadi/wiki/doku.php
• Fatemeh Panahi (fatemeh@cs.wisc.edu) http://pages.cs.wisc.edu/~fatemeh/
• Ashish Patro (patro@cs.wisc.edu)http://pages.cs.wisc.edu/~patro/
• Jordan Walker (jwalker@cs.wisc.edu)http://pages.cs.wisc.edu/~jwalker/
• Suman Banerjee (suman@cs.wisc.edu) http://pages.cs.wisc.edu/~suman/