Scheduling and Buffer Management for Soft-Real-Time VBR Traffic in Packet-Switched Networks

This paper describes four scheduling algorithms and two packet-dropping algorithms for transmitting soft-real-time variable-bit-rate traffic in a packet-switched network. Simulation results show that the first-come-first-serve algorithm, which is equivalent to the earliest-deadline-first algorithm when all packets have equal relative deadlines, outperforms the timed-token algorithm as well as two other real-time scheduling algorithms. We also simulated the last-in-firstdiscard (LIFD) algorithm as well as a more complex (1; k) packet-dropping algorithm which, for each stream, tries to drop no more than 1 packet in any sequence of k packets. We found that although the (1; k) dropping algorithm does significantly reduce the failure rate, the same reduction in this failure rate can be achieved by slightly lowering the network utilization and using the simpler LIFD algorithm.