Safe Peer-to-Peer Self-Downloading
A goal of peer-to-peer applications is to share files between users themselves rather than downloading files from file servers. Self-downloading protocols have the property that, eventually, every user downloads only from other users. Self-downloading is problematic if users disconnect from the system upon completing file downloading, because they only share with other users while connected. Yet, if users continue to arrive at a sufficient rate, self-downloading protocols are possible. One vulnerability of file sharing between users is the possibility that files or segments could be counterfeit or corrupt. Protocols that are d-safe tolerate some number of instances of faulty segments in a file being downloaded, because each segment is downloaded d times before being shared. This article shows that d-safe self-downloading is possible for a sufficiently large arrival rate of users to the system. Upper and lower connectivity and sharing bounds are given for d = 2, and simulation results show effects of relaxing assumptions about arrival rates and bandwidth.
peer-to-peer distributed systems