The Design And Implementation Of Nat Traversal Subsystem In Light-Weighted Voip System

Nowadays, VoIP applications have been so widely used, more and more companies and individuals choose Internet telephony to do real time communicating. With the increasing number of Internet networking host, many hosts are behind NAT, network address translation technology can effectively solve the problem of shortage of IPv4addresses, however NAT devices hinder the directly connecting of messages in a VoIP system, which makes NAT traversal an urgent problem for P2P applications. Therefore, research programs on the NAT traversal issue for P2P applications has important practical significance.This paper starts from the introduction NAT classification and some current mainstream NAT traversal ways, such as ALG, STUN protocol, TURN protocol and ICE protocol, then their advantages and disadvantages are described. Combined with the demand for light-weighted VoIP system, researcher designed an ICE-based way to traverse through NAT in the VoIP system, and realized the NAT traversal subsystem achieving both SIP NAT traversal and Reload NAT traversal, which makes both signal and media messages exchange directly. Then use cases were designed and the test environment was built to verify the correctness and completeness of the subsystem implementation.The results of this study solved an important and unavoidable problem in the light-weighted VoIP application, and played a significant role in promoting the development of P2P applications.