Department of Telecommunications and Media Informatics Budapest University of Technology and Economics Scalable Methods to Improve the Communications in Peer-to-Peer Networks

Scalability is a beneficial property for any kind of system. Generally, scalability ensures that the system can handle growing amounts of work in a graceful manner. In this disserta-tion, I examine the scalability of communication protocols in Peer-to-Peer (P2P) computer networks. The success of P2P file sharing applications is due to the outstanding features of this network architecture. As network participants, peers, join the system, they contribute with resources such as bandwidth, storage and processing capacity, or the content itself; moreover, the P2P architecture eliminates single points of failure. P2P can be present at various levels of network technologies, from access to backbone or provider networks, up to the P2P overlays of end-user host nodes in the Internet. In this dissertation, I examine two different P2P services: the routing in wireless ad hoc networks, and the information retrieval in structured application-level overlays built over Distributed Hash Tables. In our days, the state-of-the-art technology for ad hoc wireless communication is th