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-first-discard (LIFD) algorithm as well as a more complex (1,k) packet-dropping algorithm which, for each stream, tries to drop no more than I 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.