How Powerful Switches Should be Deployed: A Precise Estimation Based on Queuing Theory

Software-Defined Networking (SDN) provides a tractable and efficient architecture for operators to customize their network functions. Many traditional Data Center Networks (DCNs) are upgraded by SDN to improve link utilization and management flexibility, but they are lack of the instructions for selecting the substitutive SDN switches with the proper flow table space to achieve cost-effective and energy-saving networks. In this paper, we fill the gap of solving the flow table space estimation problem based on queuing theory. First, we divide the life process of a flow table entry into the packet-in process, the handling process and the serving process to establish a queuing system to estimate the least required number of the flow table entries of SDN switches. Second, we analyze the traffic distribution of DCNs to calculate the critical parameters in our model. Third, on the basis of the essence of the structured topologies in DCNs, we construct a probability model of routing strategies to quantize the influence of path selection. Comprehensive experiments show that the relative flow table space estimation error of our model can be less than 10%, which can give operators insights into the requirement of the SDN switches at specific positions.