An application- and management-based approach to ATM scheduling

Two frame-based ATM scheduling strategies, Delayed Frame Queueing (DFQ) and Virtual Frame Queueing (VFQ), are described for real-time network applicat ions. Both strategies guarantee explicit upper bounds on delay and jitter o n a per virtual connection (VC) basis without relying on per-VC queueing. T hey also resolve the disadvantages often associated with other frame-based schedulers. The DFQ scheduler employs Resource Management cells to enable w ork-conserving forwarding at intermediate nodes while retaining the option for non-work-conserving forwarding at terminal nodes. This allows delay bou nds to be uncoupled from jitter bounds. The VFQ scheduler requires no such overhead cell transmissions, but is more limited in its ability to uncouple these two types of bounds. ATM network simulation results indicate that bo th proposed disciplines offer favorable multiplexing performance in compari son to a well documented high performance service discipline. Finally, we c ontrast our proposal against the significant difficulties that alternative scheduling strategies based on bandwidth guarantees will face with regard t o network management and network synthesis issues.