| Abstract |
Tit-for-tat trading lies at the heart of many incentive mechanisms for distributed systems where participants are anonymous. However, since the standard tit-for-tat approach is restricted to bilateral exchanges, data is transferred only between peers with direct and mutual interests. Generalizing tit-for-tat to multi-lateral trades where contributions can occur along cycles of interest may improve the performance of a system in terms of faster downloads without compromising the incentive-compatibility inherent to tit-for-tat trading. In this paper, we study the potential benefits and limitations of such a generalized trading in swarm-based peer-to-peer systems. Extensive simulations are performed to evaluate different techniques and to identify the crucial parameters influencing the obtainable throughput improvements and the corresponding trade-offs. Moreover, we discuss extensions for overhead reduction and provide an optimized distributed implementation of our techniques. In summary, we find that allowing inter-swarm trades on short trading cycles can improve the throughput significantly; on the other hand, trading on long cycles does not pay off as the communication and management overhead becomes exceedingly large while the additional performance gains are marginal. |
