The influence of active measurement on unstructured peer-to-peer network

In this paper, we investigated the influence of active measurement on the unstructured P2P network. Theoretical analysis and simulation results suggested that the measurement system should get the information of existing peers as many as possible. There is an interesting phase-transition phenomena in degree distribution when the size of the measurement system increases. A P2P network mixed with a small active measurement remains as a scale-free network; however, the mixture P2P network will not remain scale-free when the size of the measurement system exceeds a threshold. Simulation results also showed that the clustering coefficients of the mixture P2P network are greater than those of the original P2P network and the average path lengths of the mixture P2P network are smaller than those of the original P2P network. We had a general conclusion: a small but dense active measurement is better than a large but loose measurement system.