Design and Implementation of Double NAT-Traversal Data Transmission System

Transfer data in only one network segment is not a sticky work. However, communication between different network segments is worth studying. Especially when one or both sides network segment behind NAT devices. This text has a brief description about the classification of NAT, and explains the problems that need to be solved about NAT traversal. According to the features of NAT and the needs of our system, this article comes up with a solution which is based on SIP. This article illustrates how to overcome the problems of NAT by SIP and the design and implementation of our system.