Networks-on-Chip (NoCs) for embedded multiprocessor architectures require special mechanisms for sharing resources such as links and queues in network routers. A widely used solution is virtual-channel flow control which prevents head-of-line blocking and isolates different data streams. However, the number of virtual channels (VCs) is limited by the available buffer space in the routers. Due to the evergrowing number of applications and mutual exclusive requirements it may not be possible to assign each application a unique VC. In this paper we present a Resource Broker (RB) which is an overarching mechanism that schedules NoC traffic. It allows predictable and efficient sharing of VCs without compromising isolation and Quality-of-Service guarantees. We show that by managing the NoC traffic with the RB, we drastically reduce blocking and improve the overall utilization and hence the system performance.