Abstract: In one embodiment, a controller is configured to establish a new multicast connection within a network without changing a path of an existing multicast connection within the network. The network can have an input stage having a total of at least n1*r1 inlet links, an output stage including r2 output switches, and n2 outlet links for each of said r2 output switches for a total of at least n2*r2 outlet links, and a middle stage including m middle switches, where m?s*Min(n1,n2) and where s=2 when r2=[9,11], s=3 when r2=[25,48], s=4 when r2=[49,99, s=5 when r2=[100,154], s=6 when r2=155,224], and s=7 when r2=[225,278 ]. The new multicast connection from an inlet link from the n1*r1 inlet links passes through at most s middle switches.

Abstract: A rearrangeably nonblocking multicast network 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.

Abstract: A three-stage network is operated in strictly nonblocking manner and 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.