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 applications. Both strategies guarantee explicit upper bounds on delay and jitter on a per virtual connection (VC) basis without relying on per-VC queueing. They also resolve the disadvantages often associated with other frame-based schedulers. The DFQ scheduler employs Resource Management cells to enable work-conserving forwarding at intermediate nodes while retaining the option for nonwork-conserving forwarding at terminal nodes. This allows delay bounds 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 both proposed disciplines offer favorable multiplexing performance in comparison to a well documented high performance service discipline. Finally, we contrast our proposal against the significant difficulties that alternative scheduling strategies based on bandwidth guarantees will face with regard to network management and network synthesis issues.