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1. O. Railio, Effect of service time distribution on BitTorrent-type peer-to-peer file transfer, Helsinki University of Technology, 2009, Master's Thesis (bib)

   Abstract: Peer-to-peer networks have recently become a significant part of the Internet's landscape. They are based on the attempts to move away from the traditional client-server model of the Internet by making each user both a sender and receiver of data. As peer-to-peer networks grow in number and expand to new uses, their research and understanding becomes increasingly important. The primary goal of this thesis is to study the effect of the peers' service time distribution on the efficiency of the whole network, which is mostly measured through the mean times that the peers spend downloading a file. This is accomplished by creating a simplified model of a peer-to-peer network, building a simple event-driven simulator and studying how it behaves when certain parameters in the simulations are varied. These parameters include the arrival rate of peers, the departure rate of seeds, the number of chunks in a file and the peer selection policy, ie. the method through which downloaders select the next piece to download, and the peer from which they will download it. In the course of the work it is discovered that the service time distribution can have a significant effect on the mean transfer times of a network. While the results are usually predictable, some results could be surprising and dependent on the type of the simulator used. The most important insight might be that one should not blindly trust a single simulator, and even a well thought-out model could need practical validation.