Evaluation and Extension of Mathematical Models of P2P Systems

Masters Thesis from the year 2007 in the subject Computer Science - General, grade: 1,3, Technical University of Darmstadt, language: English, abstract: In this thesis existing mathematical models for P2P systems are presented and evaluated. Thereby the search efficiency in structured and unstructured P2P overlays, the features and restrictions in P2P streaming applications, the service capacity in P2P file sharing systems, content download and replication times in P2P networks and many other issues are investigated. Furthermore the new extended model, possibly combining the most essential characteristics of P2P systems in a consistent way is presented. The characteristics observed in the new model are categorized in three groups according to the P2P system properties being described: the overlay parameters, the characteristics of participating peers and the resource and service characteristics. Thereafter the objectives, regulated by P2P applications users and providers, and aspects of underlying P2P systems they are interested in are observed. We consider the P2P applications Skype, Joost and KaZaA, differentiating between the application users and providers, and analyzing the technical view on the P2P system characteristics. A wide variety of existing P2P systems integrating the insights of distributed systems, databases, complexity theory and many other research areas raised inconsistencies and incompatibilities in used terminologies and abstractions. Therefore providing P2P systems interoperability and creating a common model applicable for all P2P systems became a desirable goal. In this thesis the existing P2P layer architectures considering P2P systems as a set of layers ordered according to their increasing degree of abstraction are presented. Furthermore each model layer, its input, output and functionality are described individually.