Scalable Methods to Improve the Communications in Peer-to-Peer Networks
Balázs Kovács · 2009
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 dissertation, 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 the 802.11 family. The contention-based medium access provides communication for wireless mobile nodes without the coordination of a base station. In order to access nodes in the ad hoc network indirectly, every node in such a network must provide a routing service. This dissertation discusses the scalability of ad hoc routing solutions, and proposes a routing architecture that enhances the scalability of routing in ad hoc networks. The other topic of this dissertation is related to structured P2P networks. In these networks peers are spanned by a logical topology in order to ensure fast and economic lookups. One of the first such networks is Content-Addressable Network (CAN) that has a notable drawback regarding lookup cost compared to other similar algorithms. This dissertation aims to present an enhancement of the CAN algorithm, which exploits the special features and benefits of the original solution, but constructs an overlay network that can eliminate the known shortcomings of CAN. The enhancement prepares CAN to overcome its competitors, such as Chord and Kademlia, in lookup cost and signaling traffic, and introduces a new adaptive feature for DHT routing.