Integrating coflow and circuit scheduling for optical networks

There are more and more structured traffic flows (a.k.a coflow) in today's data center networks. Completing a coflow is extremely important for various applications, e.g., MapReduce. To reduce the coflow completion time or CCT, one may increase the link capacity by applying advanced optical circuit switches in data center networks. Due to special features of optical circuit switches, both traffic scheduling and circuit scheduling will influence the CCT. However, previous solutions have some significant limitations: They consider either coflow scheduling, or circuit scheduling for only one optical circuit switch, which are both insufficient. In this paper, we study the integrated coflow and circuit scheduling (GCCS) problem with the objective to minimize the CCT, and prove its NP-hardness. We present an integrated algorithm which includes two steps, coflow scheduling and circuit scheduling, respectively. We also analyze that the proposed algorithm can achieve the approximation ratio O(h)O(h) in most practical situations, where hh is the maximum number of ports among all lightpaths. Through large-scale simulations, we demonstrate that the integrated solution can significantly reduce the CCT by about 43-70 percent compared with the state-of-The-Art coflow scheduler for optical networks.