LANC: Locality-aware network coding for better P2P traffic localization

摘要

As ISPs begin to cooperate to expose their network locality information as services, e.g., P4P, solutions based on locality information provision for P2P traffic localization will soon approach their capability limits. A natural question is: can we do any better provided that no further locality information improvement can be made? This paper shows how the utility of locality information could be limited by conventional P2P data scheduling algorithms. Even sophisticated data scheduling algorithms such as the local rarest first could not take full advantage of the locality information. Network coding's simplified data scheduling makes it competent for improving P2P application's throughput. However, its potential for P2P traffic reduction has not been fully recognized. This paper proposes the locality-aware network coding (LANC) that uses locality information in both the topology construction and downloading decision, and demonstrates its exceptional ability for inter-domain P2P traffic reduction. The randomization introduced by network coding enhances the chance for a peer to find innovative blocks in its neighborhood. Aided by proper locality-awareness, the probability for a peer to get innovative blocks from its proximity will increase as well, resulting in more efficient use of network resources. Extensive simulation results show that LANC can significantly reduce inter-domain P2P traffic without sacrificing application-level performance. Aided by the same locality knowledge, the inter-domain traffic of LANC in most cases are less than 50% of the current best approach that does not use network coding. We also show that this property holds when the tit-for-tat incentive mechanism is introduced or the overlay topology changes dynamically.