Modeling Faulty, Unstructured P2P Overlays

Unstructured peer-to-peer systems represent viable candidates for supporting distributed applications with frequent node failures. This paper presents a framework to study the reliability of evolving overlay networks in presence of faulty nodes. We focus on the node degree distribution, an important metric to understand whether the topology of the overlay can be maintained in presence of peer churns. From the degree distribution, other metrics can be estimated such as the diameter of the net. Two protocols are considered, which differ in the way peers attach to other nodes. Numerical results are compared with those obtained through simulation. They confirm that the proposed model can be factually exploited to adapt the peers´ behavior and preserve the desired topology of the overlay.