NAT-Traversal Technology For VNC

VNC (Virtual Network Computing) is a screen sharing and remote operation tools developed by the AT & T Laboratories in Cambridge, it supports multiple operating systems, it can be used to variety of applications such as remote office, remote technical support, With the rapid development of the Internet, the number of Internet user are growing fast. Otherwise Ipv6 is not yet universal,the problem of IP address shortage is becoming more and more serious., IP address shortage problem is becoming increasingly severe, NAT (Network Address Translate) has become the universal solution to this problem. But NAT has also brought some issue, the external network terminal can not directly access to the terminal behind NAT, it is couse the communications between VNC client and server which is located behind NAT became very difficult. How to make VNC work through NAT become an important issue for VNC applications.In this paper, we do a in-depth research with NAT and conducted things. Through analysis and comparison with the existent NAT traversal technology, rise a NAT traversal comprehensive solution for VNC. Because VNC use both UDP protocol and TCP protocol to transmit the information. This solution includes UDP traversal and TCP traversal two parts. UDP traversal part used the STUN protocol which is relatively sophisticated, and used widely, but the TCP traversal part, as which requires to three-way handsake and status changes, is much more complexed than UDP one. at present the industry has not yet a has widely recognized solution, by analysis and comparison, through several TCP traversal technical we finally chose the STUNT protocal for Nuss group to carry out basic development. However, the TCP traversal solution based on STUNT still have many problems, this paper did a in-depth research for these issues and improve the STUNT model to achieve better success rate. Finally, we add the port prediction algorithm, to solve the Symmetric NAT traversal problem which is not mentioned from STUN and STUNT protocol.Finally this paper gave detailed description for the overall program architecture and work flow, builded an experimental environment for test. experimental result is demanstrated that the program is feasible.