Admission and congestion control mechanisms are integral parts of any Quality of Service (QoS) design for networks that support integrated traffic. While an admission control algorithm helps in delivering the assured performance, a congestion control algorithm regulates traffic injection to avoid network saturation. 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, which have been used in designing clusters. 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. A mixed workload consisting of best effort, real-time, and control traffic is used to investigate the effectiveness of the proposed schemes.
Simulation results with a single router (8-port) cluster and a 2-D mesh network cluster 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/NIC to regulate traffic injection.