Second, the links in networks vary on the transmission rates and costs according to their unique features [9], e.g., the distances and physical optical fiber facilities between data centers. However, the existing routing strategy among data centers fails to exploit the link diversity of data center networks. Due to the storage and computation capacity constraints, not all tasks can be placed onto the same server, on which their corresponding data reside. It is unavoidable that certain data must be downloaded from a remote server. In this case,routing strategy matter son the transmission cost. As indicated by
Jin et al. [10], the transmission cost, e.g., energy, nearly proportional to the number of network link used. The more link used, the higher cost will be incurred. Therefore, it is essential to lower the number of links used while satisfying all the transmission requirements.