Enhanced peer discovery for multiaccess peer-to-peer networks: Master's thesis

This thesis includes the design, implementation and evaluation of a multiaccess peer-to-peer content distribution prototype based on BitTorrent. The prototype is designed to enhance the current BitTorrent in terms of download duration and traffic locality in an overlapping multiaccess environment. The thesis begins with related state of the art including future ways of networking as well as current state of peer-to-peer networks, object resolution and mobility management. Experiments with conventional BitTorrent show the importance of early stage peer discoveries by the BitTorrent tracker. We therefore enhanced the peer discovery process of BitTorrent and divided the functions of the tracker hierarchically into two layers. The higher layer global tracker keeps track of local trackers, while the local trackers maintain a list of peers in their area of the network. The peer in our prototype retrieves the content locally from its own network whenever possible with extended BitTorrent signalling. While retrieving the content in an overlapping multiaccess environment, the mobile peer in the prototype recognises also a new connection to other networks. It is able to use this connection simultaneously with the previous one. The prototype implementation and evaluation show the feasibility of multiaccess in the content distribution prototype and present the advantages of employing the multiaccess prototype instead of conventional BitTorrent in overlapping multiaccess environments in static and pedestrian mobility scenarios. The inter-network traffic was also reduced to almost zero with the prototype in both scenarios.