Over the past decade BitTorrent has established itself as the virtual standard for P2P file sharing in the Internet. However, it is currently not possible to investigate BitTorrent with ns-3 due to the unavailability of an according application model. In this paper we eliminate this burden. We present a highly modular BitTorrent model which allows for the easy simulation of different BitTorrent systems such as file sharing as well as present and future BitTorrent-based Video-on-Demand systems.