In this report we study the general problem of parallel data redistribution over a network. Given a set of communications between two parallel machines interconnected by a backbone, we wish to minimize the total time required for the completion of all communications assuming that communications can be preempted and that preemption comes with an extra cost. Our problem, called k-Preemptive bipartite scheduling (KPBS) is proven to be NP-Complete. Moreover we prove that approximating KPBS problem within a ratio number smaller that4/3 is impossible unless P=NP. In spite of this negative result, we study a lower bound of this problem, and we propose an approximatio- n algorithm with ratio 2 and fast heuristics.