InfiniBand Architecture (IBA) has been ratified as a new industry standard for the server Input/Output (I/O) and inter-processor communication. It defines a switch-based interconnection technology with highbandwidth and low-latency suitable for constructing high-speed networks in cluster computing systems. In this paper, we propose an efficient flow control mechanism for InfiniBand networks in order to reduce the delay, blocking probability, and mean queue length as well as improve the system utilization. Consequently, this mechanism can enhance the Quality-of-Service (QoS) of InfiniBand. The principle of maximum entropy (ME) is adopted as an effective methodology to analyze the new mechanism with the generalized exponential (GE)-Type distribution for modeling the inter-arrival times and service times of the input traffic. Typical performance measures obtained from simulation experiments are included to validate the accuracy of the analytical results.