Bittorent Simulator in Erlang

Abstract: This master thesis examined how different behavior of bittorrent clients and trackers affect the simulation in various scenarios such as different network topologies, greedy behavior of downloading clients or choices of algorithms by the downloading clients. The thesis also includes the construction of a network simulator, a modular bittorrent client and a modular bittorrent tracker to support a wide range of options for the bittorrent simulator. These options can be combined to make new scenarios for the simulator to run and results will be presented graphically. Even the algorithms of the modular structure can be easily exchanged to try out new ideas of how things should work to find out how the algorithm behaves under certain circumstances and how it affects the swarm. Simulations were made to examine behavior when clients had different configurations of the choking algorithm, clients had different sizes of their sub pieces, clients had different distance to the seeder, clients used different piece selection algorithm. In the case of the piece selection algorithms using only a few seeders, the algorithms performed similar to each other which was contrary to our initial expectation that the algorithm rarest first would perform better than the naive order algorithm.