Next-generation applications will impose diverse performance requirements (with respect to delay, throughput, etc.) on operating systems. Current operating systems offer a single class of ``best-effort'' service to all the applications. Next-generation operating systems can increase the overall utility of the available resources by supporting multiple service classes and aligning services with application needs. To achieve this objective, we are developing processor scheduling mechanisms, I/O subsystems, as well as higher layer protocols necessary for efficient processing and streaming of data at the end-station.