Linear complexity algorithms for bandwidth reservations and delay guarantees in input-queued switches with no speedup

We present several fast, practical linear-complexity scheduling algorithms that enable provision of various quality-of-service (QoS) guarantees in an input-queued switch with no speedup. Specifically, our algorithms provide per-virtual-circuit transmission rate and cell delay guarantees using a credit-based bandwidth reservation scheme. The novelties of our algorithms derive from judicious choices of edge weights in a bipartite matching problem. The edge weights are certain functions of the amount and waiting times of queued cells and credits received by a virtual circuit. By using a linear-complexity variation of the well-known stable marriage matching algorithm, we demonstrate by simulations that the edge weights are bounded. This implies various QoS guarantees or contracts about rate and cell delays. Network management can then provide these contracts to the clients. We present several different algorithms of differing complexity and power (as measured by the usefulness of each algorithm's contract). While most of this paper is devoted to the "soft" guarantees demonstrated by simulations, we also list a few "hard" theoretical guarantees for some of our algorithms (proved in our full report). As can be expected, the provable guarantees are weaker than the observed performance bounds in simulations.