A Survey of NAT Behavior Discovery in VoIP Applications

Abstract

Because of the foreseeing depletion of Internet Protocol (IP) addresses, Network Address Translation (NAT) is ubiquitously deployed to allow hosts to connect to the Internet through a single shared public IP address, which is a popular approach in deploying wireless local area network (WLAN). Although NAT proves to work well with traditional client/server applications, its existence and non-standard behaviors are the major problem which cripples voice over IP (VoIP) applications. In addition to some efforts which attempt to devise complicated protocols to tackle all NAT varieties, there are also efforts in Internet communities trying to standardize the behaviors of NAT. Therefore, it becomes crucial for a network device to discover the existence of NAT in its subnet and to determine the NAT behaviors, so that it can choose the optimal NAT traversal mechanisms to apply. In this paper, we surveyed the divergent NAT behaviors and then proposed a simplified NAT behavior discovery approach which is more suitable for VoIP applications. The proposed approach can reduce the call establishment time of VoIP applications, which is useful in scenarios where VoIP devices are administrated within a specific domain, e.g., 3G cellular networks.