NATRON : overlay routing to oblivious destinations

Abstract

This thesis presents NATRON, a system in which an overlay network of nodes cooperates to improve unicast routing to non-participating hosts. Previous overlay systems have used overlay routing to improve communication between participating hosts; they were unable to exploit overlay routing to non-participating hosts. NATRON uses a combination of IP tunneling and network address translation to allow members of the overlay to communicate with hosts outside the overlay network via other overlay members. In order to estimate the potential performance improvement a system like NATRON might provide, we performed an exhaustive test on a multi-site Internet testbed. Our results show that a system that always guesses the best intermediate node could reduce the average HTTP transfer time by 18% and reduce the number of downloads lasting longer than 30 seconds by 16%. We implemented a working NATRON and a heuristic for choosing intermediate overlay nodes, but we find that our heuristic can only exploit 22% of the potential performance gains. We conclude that overlay routing to oblivious hosts has good potential for performance enhancement but further work is needed to develop a path choice heuristic.