The InfiniBand Architecture (IBA) is a new industry standard architecture for server I/O and interprocessor communication. InfiniBand is very likely to become the de facto standard in a few years. It is being developed by the InfiniBand Trade Association (IBTA) to provide the levels of reliability, availability, performance, scalability, and quality of service (QoS) necessary for present and future server systems. The provision of QoS in data communication networks is currently the focus of much discussion and research in industry and academia. IBA enables QoS support with some mechanisms. In this paper, we examine these mechanisms and describe a way to use them. We propose a traffic segregation strategy based on mean bandwidth requirements. Moreover, we propose a very effective strategy to compute the virtual lane arbitration tables for IBA switches. We evaluate our proposal with different network topologies. Performance results show that, with a correct treatment of each traffic class in the arbitration of the output port, every traffic class meets its QoS requirements.