Abstract: A rearrangeably nonblocking multicast network in accordance with the invention includes an input stage having r1 switches and n1 inlet links for each of r1 switches, an output stage having r2 switches and n2 outlet links for each of r2 switches. The network also has a middle stage of m switches, and each middle switch has at least one link connected to each input switch for a total of at least r1 first internal links and at least one link connected to each output switch for a total of at least r2 second internal links, where m?n1+n2. The network has all multicast connections set up such that each multicast connection passes through at most two middle switches to be connected to the destination outlet links. When the number of inlet links in each input switch n1 is equal to the number of outlet links in each output switch n2, and n1=n2=n, a three-stage network is operated in rearrangeably nonblocking manner in accordance with the invention, where m?2*n.

Abstract: A three-stage network is operated in strictly nonblocking manner in accordance with the invention includes an input stage having r1 switches and n1 inlet links for each of r1 switches, an output stage having r2 switches and n2 outlet links for each of r2 switches. The network also has a middle stage of m switches, and each middle switch has at least one link connected to each input switch for a total of at least r1 first internal links and at least one link connected to each output switch for a total of at least r2 second internal links, where m?2*n1+n2?1. In one embodiment, each multicast connection is set up through such a three-stage network by use of at most two switches in the middle stage. When the number of inlet links in each input switch n1 is equal to the number of outlet links in each output switch n2, and n1=n2=n, a three-stage network is operated in strictly nonblocking manner in accordance with the invention if m?3*n?1.