The Darwin system runs on FreeBSD 3.3 or 3.4 and includes kernel modifications for the HFSC scheduler and input port router packet classification and packet processing, the delegate runtime environment, the Beagle signaling protocol, and a number of utilities.
Darwin includes two domain-specific execution environments that were developed in part under Libra. The first one is the delegate runtime environment, which supports router extensions performing tasks in the area of QoS and traffic management. The second one is part of the Beagle signaling protocol and supports router extensions for setting up customizable resource sharing across flows.