Optimal multicast scheduling in input-queued switches

This paper focuses on multicast support in input-queued packet switches with internal multicast capabilities. Besides providing an overview of some alternative architectures and algorithms proposed in the literature, the paper brings two original contributions. First, multicast traffic admissibility conditions are defined, and theorems showing intrinsic performance losses of input-queued with respect to output-queued switch architectures are proved. Second, the optimal scheduling discipline in transferring multicast packets from switch inputs to switch outputs is defined. From the definition of the optimal multicast scheduling discipline, the formal characterization of the sustainable multicast traffic region naturally follows. Both results aim at a correct formal definition of the considered problem, in order to identify a sound starting point for the design of heuristics that approximate the optimal solution at a complexity compatible with available technologies