Efficient nonblocking multicast communications on baseline networks

This article explores the problem of efficiently multicasting packets on the baseline network in accordance with a given set of multicast communications, A baseline network is a multistage interconnection network (MW) with N inputs and N outputs as well as log N stages of 2 x 2 switches. The baseline network construction with wraparound connections leads us to propose a new scheme for nonblocking packet multicasts. Previous approaches use a cascade of various MINs to multicast packets in a finite number of steps. Some other use single MINs to recycle and copy packets repeatedly until the multicast is done. Our proposed scheme exhibits a different approach from the previous ones, yet possessing many desirable features of theirs. Our scheme employs a log(2) N-stage baseline network with wraparound connections. It is capable of accomplishing any multiple multicast in four finite passes. The first two passes replicate individual packets simultaneously. Then the subsequent two passes route these packets to the destinations. We demonstrate that paths created in the four passes are all link-disjoint so that nonblocking multicast is achieved. We further look into a few possible pipeline implementations of the proposed scheme. By unrolling some passes, we obtain a number of pipeline variations from the basic log, N-stage baseline network. These variations allow us to process successive multicast runs in an overlapped fashion. (C) 1999 Elsevier Science B.V. All rights reserved.