CORP: A COoperative file Replication Protocol for structured P2P networks

File replication and file consistency maintenance are two important protocols for achieving overall high performance of peer-to-peer file sharing systems. In spite of the significant dependency of consistency maintenance on file replication, there has been little file replication research devoted to tackling the dependency issue. Most traditional file replication protocols focus on improving file lookup efficiency without considering the subsequent consistency maintenance. This paper presents a COoperative file Replication Protocol (CORP). CORP observes a set of factors including file update rate, file popularity, node available capacity, file load and node locality that affect the efficiency of consistency maintenance. It considers these factors to achieve high efficiency not only in file replication but also in consistency maintenance. CORP generates less replicas and optimally chooses infrequently-updated or popular files to replicate. In addition, it makes file replicas in physically close nodes. Further, CORP can dynamically adjust the number of replicas based on ever-changing file popularity and visit pattern. Simulation results demonstrate the efficiency and effectiveness of CORP in comparison with other file replication protocols. It dramatically reduces the overhead of both file replication and consistency maintenance. Moreover, it yields significant improvement in reducing overloaded nodes.