BitTorrent is a popular, open-source content distribution system that is conducive for distribution of large-volume files. In this paper, we first model the parallel downloading problem as directed graph and discuss possible improving directions. Then a smart connection management algorithm is proposed, which introduces the notion of content group and sub-tracker, and decentralizes the decision process performed at the tracker for transfer coordination. Simulations show that by increasing content availability to the clients from their immediate neighbors, it can significantly improve the efficiency of distribution.