关键词：P2P系统；分布式大型LES网络；稳定性；罕见块规则
摘 要：P2P systems provide a scalable solution for distributing large les in a network. The le is split into many chunks, and peers contact other peers to collect missing chunks to eventually complete the entire le. The so-called `rare chunk' phenomenon, where a single chunk becomes rare and prevents peers from completing the le, is a threat to the stability of such systems. A protocol that forces peers to download the rarest chunk in the network rst would solve this issue, however this solution requires global chunk availability information that is not readily available. We look for a distributed approximation to this solution. Although heuristics exist which perform well in practice, formal proofs of stability of such systems were lacking. In this document, we demonstrate a new system based on an approximate rare-chunk rule, allowing for completely distributed le sharing while retaining scalability and stability. We assume non-altruistic peers and the seed is required to make only a minimal contribution.