This paper introduces a Combinatory Optimization Problem (COP) which captures the performance in cooperation of a P2P Streaming Network, considered at the buffer level. A new family of strategies of cooperation is defined, which represents the order of query of pieces in a communication between peers. We define a measure of quality for each strategy, based on the most shocking video streaming parameters, namely the continuity and the start-up latency. Our aim is o find quasi-optimal strategies inside the proposed family, by means of on a model based on an Asymmetric Traveling Salesman Problem (ATSP). Finally, we solve this ATSP using an ACO (Ant Colony Optimization)-based algorithm. The results show substantial improvement with this approach, once compared with the ones obtained by previous defined strategies of cooperation.