Abstract: This paper presents CHANNELS, a run-time system for network protocol processing. CHANNELS is especially intended and optimized for transport systems supporting multimedia applications on high-speed networks. Additionally to the traditional features of a run-time system like the scheduling of the processing of different protocols, the provision of dedicated facilities such as timer, buffer and mapping table libraries for protocol implementation and the support of communication to adjacent protocol entities, network devices and user processes, CHANNELS enables the implementation of sophisticated protocols which require real-time and parallel processing capabilities, or dynamic protocol configuration support. CHANNELS is implemented in the C++ programming language and one prototype is embedded in the SUN/UNIX kernel.