Analysis of different churn models in chord based overlay networks

Structured Overlays are emerged as a suitable infrastructure for building distributed and self organizing architecture. They are used for a range of applications such as resilient routing networks, distributed storage and backup system and distributed spam filters etc. However, due to their fixed architecture their performance is greatly affected by continuous process of nodes joining or leaving the network (churn). So, in order to design an effective overlay application, we should evaluate its performance keeping node dynamism in mind. To model node dynamism the simulation environments provides different churn generators. The goal of this paper is to study these churn generators to understand their churn generation trends, which will help the researchers in selecting appropriate churn generator for testing their overlay application in OverSim simulation environment. Specifically, Lifetime, Pareto and Random churn generators are evaluated to provide a comparative analysis. This simulation study concludes that the lifetime churn (based on weibull distribution) provides highest node dynamism and thus have significant impact on the overlay´s performance. This study also emphasis on the fact that churn rate is not solely dependent on the selection of churn generator but we can increase or decrease the churn rate by varying mean life time parameter in lifetime and pareto churn generation and target mobility delay in random churn generation.