An empirical study of the global behavior of a structured overlay network

Distributed applications built on top of Structured Overlay Networks (SONs) operate based on certain assurances from the underlying Peer-to-Peer network. Such applications continue to increase in scale, becoming more complex and difficult to manage. The situation becomes worse if the behavior of underlying SON is non-deterministic or even unknown for a given scenario. This implies non-trivial questions: what behavior should the application layer expect from the underlying SON in a given scenario? Under what conditions should a SON exhibit resiliency against an extremely hostile environment? Ideally, the behavior of a complex system such as a SON needs to be defined for every possible operating condition. Existing literature lacks a systematic and in-depth study of the global behavior of a SON. This work is a step towards answering those questions, which starts by proposing an organization of the global operating space of a SON, also defines the term “behavior”, with respect to a SON. In order to conduct the experimental study, an existing ring-based SON, namely Beernet, is chosen as a representative. As the entire operating space of a SON is extremely large, due to space limitation, this paper presents the first results of our investigation, the behavior of Beernet along the dimension of Churn. The study assesses behaviors like key availability, updates, replica management, and failed transactions, as a function of churn up to 100% node turnover per time unit. The result shows that, continuous injection of extremely high churn causes the ring to be dissolved, creating isolation of peers. However, at such a high node turnover of 100% per 5s, there are instances, where the % of failed transactions didn´t reach 100%, especially in cases, when the join events dominate failures during initial period.