Admission and congestion control mechanisms are integral parts of any Quality of Service (QoS) design for networks that support integrated traffic. In this paper we propose an-admission control algorithm and a congestion control algorithm for clusters, which are increasingly being used in a diverse set of applications that require QoS guarantees. The uniqueness of our approach is that we develop these algorithms for wormhole-switched networks. We use QoS-capable wormhole routers and QoS-capable network interface cards (NICs), referred to as Host Channel Adapters (HCAs) in InfiniBand™ Architecture (IBA), to evaluate the effectiveness of these algorithms. The admission control is applied at the HCAs and the routers, while the congestion control is deployed only at the HCAs. Simulation results indicate that the admission and congestion control algorithms are quite effective in delivering the assured performance. The proposed credit-based congestion control algorithm is simple and practical in that it relies on hardware already available in the HCA to regulate traffic injection.