The i-QOCF (iterative quasi-oldest-cell-first) algorithm for input-queued ATM switches

Abstract

This paper proposes a new scheduling algorithm for input-queued ATM switches, called the iterative quasi-oldest-cell-first (i-QOCF) algorithm. In i-QOCF, each input port and each output port maintains its own list. The length of the list can be N,2/spl times/N,...,B/spl times/N, where B is the size of the buffer that queues cells destined for an output port. The list maintained by an input port contains the identifiers of those output ports to which that input port will send a cell. The list maintained by an output port contains the identifiers of input ports which have a cell destined for that output port. We show the performance of i-QOCF and results in which we compare i-QOCF with i-OCF in terms of cell delay time. We find that an input-queued ATM switch with i-QOCF and virtual output queue (VOQ) can achieve 100% throughput for independent arrival processes. The 3-QOCF is enough to achieve convergence during one cell time. If we use a 3-QOCF in which the list length is 3/spl times/N, then its cell delay time performance is almost the same as that of a 4-OCF.