A Balanced Consistency Maintenance Protocol for Structured P2P Systems

A fundamental challenge of managing mutable data replication in a Peer-to-Peer (P2P) system is how to efficiently maintain consistency under various sharing patterns with heterogeneous resource capabilities. This paper presents a framework for balanced consistency maintenance (BCoM) in structured P2P systems. Replica nodes of each object are organized into a tree for disseminating updates, and a sliding window update protocol is developed to bound the consistency. The effect of window size in response to dynamic network conditions, workload updates and resource limits is analyzed through a queueing model. This enables us to balance availability, performance and consistency strictness for various application requirements. On top of the dissemination tree, two enhancements are proposed: a fast recovery scheme to strengthen the robustness against node and link failures; and a node migration policy to remove and prevent the bottleneck for better system performance. Simulations are conducted using P2PSim to evaluate BCoM in comparison to SCOPE. The experimental results demonstrate that BCoM significantly improves the availability of SCOPE by lowering the discard rate from almost 100% to 5% with slight increase in latency.