Towards a Better Understanding of Churn in Peer-to-Peer Networks

The dynamics of peer participation, or churn, are an inherent property of Peer-to-Peer (P2P) systems that should be incorporated in both the design and evaluation of P2P systems. This requires a proper characterization of churn in real-world P2P networks. However, the few previous measurement-based studies on the characterization of P2P systems have used either unrepresentative group of peers or coarse-grain mea- surements. In this extended abstract, we characterize churn in the Gnutella network based on fine-grained monitoring of the entire population. We developed a new crawler that can capture a complete snapshot of Gnutella network within a few minutes. This not only improves the accuracy, by reducing distortion in captured snap- shots, but it also increase the granularity of captured dy- namics. We present our preliminary characterizations of peer uptime and discuss their implications. In par- ticular, we show that peer uptime follows a power-law distribution rather than the commonly assumed Poisson distribution. In a nutshell, a large portion of up peers are highly stable, yet the remaining peers turnover very quickly. Keywords—Peer-to-Peer, Churn, Characterization, Gnutella