Shrinking MTU to improve fairness among TCP flows in data center networks

TCP is widely used in the communications between servers in data centers. However, TCP has scaling limit that its ability to provide fair sharing at bottleneck link is reduced as the number of competing flows increases. Such limit is common in current data center networks and causes unfairness among TCP flows on a small time scale. The unfairness would add unpredictable delay to short flows, which would affect the user experiences of soft real-time applications. In this paper, we propose a simple and cost-effective method - shrinking MTU - to improve the fairness among TCP flows. Through model analysis and extensive simulations, the fairness on a small time scale is improved and the completion time of short flows is reduced by decreasing MTU size.