| Summary: | 碩士 === 國立交通大學 === 資訊科學與工程研究所 === 97 === In this thesis, we proposed a Context Aware Network Address Translation (NAT) Traversal scheme that can use NAT information to adjust its behavior when it tries to establish a connection across NATs. Many researchers have proposed techniques to tackle the NAT traversal problem. Among the previous proposals of NAT traversal techniques, Interactivity Connectivity Establishment (ICE) is the most acknowledged approach to establishing a connection across NATs. Although ICE is a very powerful connectivity establishment mechanism, it still possesses some drawbacks. First, ICE performs a systematical and exhaustive test procedure to find a connection from all possible paths between two peers; however, this procedure introduces a long delay or excessive message exchanges for setting up a connection. Second, ICE may fail in finding a direct connection that exists between the two communicating peers.
In order to shorten the connectivity check delay, reduce the number of message exchanges, and increase the overall direction rates, we propose a Context Aware NAT (CAN) traversal scheme for finding a connection between two communicating peers behind NATs. The main idea of CAN is that user agents (UAs) exchange the NAT information, such as NAT types, Hairpin Capability and Connection Tracking and Binding feature, that can help UAs to eliminate unnecessary connectivity checks, shorten the delay of connectivity checks, and increase Direct Connection Rate (DCR). We have implemented CAN and compared the performance of CAN and ICE. The experimental results show that CAN outperforms ICE in terms of latencies and message exchanges for connectivity checks, and direct connection rate.
Furthermore, CAN is compatible with standard NAT traversal mechanisms, such as TURN and STUN, and can work with other mechanisms for increasing DCR.
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