Availability in P2P based online social networks

Despite their tremendous success, centrally controlled cloud based solutions for social media networking have inherent issues related to privacy and user control. Alternatively, a decentralized approach can be used, but ensuring content availability will be the major challenge. In this work, we propose a time-based user grouping and replication protocol that ensures content availability for decentralized sharing of online social media. The protocol exploits cyclic diurnal patterns in user uptime behaviors to ensure content persistence with minimal replication overhead. We also introduce the concept of β-availability that represents the probability that at least β members of a replication group will be online at any given time. We present a mathematical model for measuring β-availability as a function of peer-uptime duration and replication group size. Simulation results show that our protocol achieves high content persistence without incurring significant network and storage overheads.