GeWave: Geographically-Aware Wave for File Consistency Maintenance in P2P Systems

File consistency maintenance in P2P systems is a technique for maintaining consistency between files and their replicas. Most traditional consistency maintenance methods depend on either message spreading or structure for update propagation by pushing. Message spreading generates high overhead due to redundant messages, and cannot guarantee that every replica node receives an update. Structure-based pushing methods reduce the overhead but cannot guarantee timely consistency in churn. Moreover, most methods are unable to consider physical proximity to improve efficiency. To further reduce update overhead, enhance guarantee of consistency, and take proximity into account, this paper presents a geographically-aware Wave method (GeWave). Depending on adaptive polling in a dynamic structure, GeWave avoids redundant file updates by dynamically adapting to time-varying file update and query rates, and ensures the consistency of query results even in churn. Furthermore, it conducts update propagation between geographically close nodes in a distributed manner. Simulation results demonstrate the efficiency of GeWave in comparison with other representative consistency maintenance schemes. It dramatically reduces the overhead and yields significant improvements on efficiency and scalability of file consistency maintenance schemes.