PeerSim: A scalable P2P simulator The key features of peer-to-peer (P2P) systems are scalability and dynamism. The evaluation of a P2P protocol in realistic environments is very expensive and difficult to reproduce, so simulation is crucial in P2P research. PeerSim is an extremely scalable simulation environment that supports dynamic scenarios such as churn and other failure models. Protocols need to be specifically implemented for thePeerSim Java API, but with a reasonable effort they can be evolved into a real implementation. Testing in specified parameter-spaces is supported as well. PeerSim started out as a tool for our own research.