Exploring the Feasibility of Reputation Models for Improving P2P Routing under Churn

Reputation mechanisms help peer-to-peer (P2P) networks to detect and avoid unreliable or uncooperative peers. Recently, it has been discussed that routing protocols can be improved by conditioning routing decisions to the past behavior of forwarding peers. However, churn — the continuous process of node arrival and departure — may severely hinder the applicability of rating mechanisms. In particular, short lifetimes mean that reputations are often generated from a small number of transactions. To examine how high rates of churn affect rating mechanisms, this paper introduces an analytical model to compute at which rate transactions has to be performed so that the generated reputations are sufficiently reliable. We then propose a new routing protocol for structured P2P systems that exploits reputation to improve the decision about which neighbor choose as next hop. Our results demonstrate that routing algorithms can extract substantial benefits from reputations even when peer lifetimes are short.