現今網路技術快速發展，連網裝置的數量也愈來愈多且多樣化，為了解決IP位址短缺及提升 網路安全性，大部份的連網裝置都會透過網路位址轉換器(Network Address Translator；NAT)與 其它裝置互聯，由於NAT會提供網路位址的轉換，並對封包的傳輸有所限制，導致裝置與裝置之 間的傳輸會因封包無法穿透NAT而出現問題。因此，如何穿透NAT變成一個重要的研究議題。使 用中繼伺服器(Relay Server)的協助來穿透NAT雖然有較高的成功穿透率，但有傳輸效率及浪費網 路頻寬等問題，為了提升傳輸效率及節省網路頻寬，很多研究都著重在如何以點對點(Peer-to-Peer; P2P)的方式來穿透NAT， 但在對稱式(symmetric) NAT裝置愈來愈普及的情況下， 使用點對點的 方式來穿透NAT的成功率仍顯不足。有鑒於此，在這篇論文中，我們先後建立中繼連線及點對點 直接連線，並提出一個協同式NAT穿透方法，以兼顧成功穿透率、傳輸效率及節省網路頻寬的使用。

Nowadays, with the rapid growth of Internet technologies and the proliferation of diverse devices connected to the Internet, most devices connect with each other through Network Address Translator (NAT) in order to handle the shortage of IP address and promote network security. Since NAT is a methodology of remapping one IP address space into another and restricting packet transmission, packets transmitted between devices are most likely blocked by NAT. Therefore, how to traverse NAT is an important research issue. Although traversing NAT by the aid of a relay server has a higher success rate, it may encounter the problems of poor transmission efficiency and waste of network bandwidth. In order to enhance transmission efficiency and economize the use of network bandwidth, many researches put emphasis on Peer-to-Peer (P2P) NAT traversal. However, since the symmetric NAT devices are more and more popular, the success rate of P2P NAT traversal is still insufficient. In view of this, in this paper, the relay connection and the P2P direct connection are established in succession. A collaborative NAT traversal method is proposed to enhance success rate of NAT traversal as well as transmission efficiency and economize the use of network bandwidth.