NBA – NAT Behavior Aware TCP Traversal Scheme

• Main Authors: Liu, Kun-Ying, 劉坤穎
• Other Authors: Tseng, Chien-Chao
• Format: Others
• Language: en_US
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/65934423035049304032

碩士 === 國立交通大學 === 資訊科學與工程研究所 === 98 === In this thesis, we propose a Network Address Translation (NAT) Behavior Aware, henceforth referred to as NBA, scheme for TCP NAT Traversals. Many researchers have proposed techniques to tackle the TCP NAT traversal problem. However, previous TCP NAT traversal research focuses on whether a specific TCP signaling sequence can establish a direct connection successfully between two peers behind NATs. Because each signaling sequence has its own applicable NAT types, brute force connectivity check may induce a long delay or excessive message exchanges for setting up a connec-tion. Therefore, NBA utilize TCP state tracking behaviors of NATs as a priori know-ledge to select the most appropriate Traversal method for the connectivity check be-tween two communicating peers behind. As a consequence, it can eliminate unnecessary checks, shorten the connectivity check delay, reduce the number of message exchanges, and sometimes help to avoid failure in connectivity check that ought to succeed. With NBA, user agents (UAs) collect the NAT information such as mapping rules, filtering rules and TCP state tracking behaviors, and report the collected information to an NBA server. When two UAs intend to establish a communication session, the server consults the information reported by the two UAs, determines the best traversal method, if exists, and informs the two UAs to check connectivity with the selected method. We have implemented NBA and compared the performance of NBA with both sequential connectivity check (SCC) scheme and parallel connectivity check (PCC) schemes. The experimental results show that NBA achieves the same direct connection ratio as SCC and PCC do. Furthermore, NBA outperforms SCC in terms of latencies and PCC in system resources utilizations for connectivity checks.