Improvement of Chord overlay for P2PSIP-based Communication Systems

摘要

Chord has been suggested by IETF P2PSIP working group as mandatory overlay technology in the future P2PSIP-based communication systems. Chord allows for the available peer/resource lookup in no more than log N hops, where N is the total number of the peers in the overlay network. However, as a protocol originally designed for background downloading applications, Chord has a few drawbacks when supporting P2PSIP real-time communication systems. These drawbacks are related to ID assignment, the relation between ID and physical location, the routing styles and lack of cache, etc. In this paper, we investigate several approaches that can improve the efficiency of the peer/resource lookup algorithm. After that, we first use the formal verification to check the correctness of the proposed Bi- Chord and Recursive routing approaches, and then implement two systems with 512 P2PSIP peers (Chord-based and improved Chord based P2PSIP communication systems) for evaluation. The evaluation includes number of hops, message flows, and practicality from theoretical point of view, and the comparison of the delay in two systems according to the measurement. We get the conclusion that the combination of Bi-Chord, Cache entry record, and Semi-Recursive routing is most suitable for P2PSIPbased communication systems. Finally, we include the conclusions and future work.