Design of multicast controller for high-capacity Internet router

Introduction: Multicasting in high-capacity Internet has not been resolved yet. Multicast traffic that we consider has one source and multiple destinations. There are two main approaches for forwarding of the multicast traffic through a crossbar. In the case of unicast crossbars, an input has to replicate a multicast packet, as many times as there are output ports to which that packet is bound. So, if the input sources popular multicast sessions, it might become clogged easily. Alternatively, the crossbar might have a multicast capability, meaning that one input might simultaneously send packets to multiple outputs. However, it was shown that even if the optimal scheduling algorithm is applied to the router, the speedup required to pass an admissible traffic increases with the number of router ports [1]. On the other hand, the high-capacity router could handle the multicast traffic well when the packets are circulated through a unicast fabric [2, 3]. The input is allowed to send incoming packets just to the limited number of the ports belonging to the multicast set. In the next iteration, ports which received forwarded multicast packets keep forwarding them, to the limited number of ports from the multicast set which did not receive that packet in previous iterations. As a consequence, transmission load of the input port is spread over all ports in the multicast set. Packet circulation is simple to implement. Packets are forwarded according to the circulation tree corresponding to that multicast session. The circulation tree is updated when users in the network join or leave the multicast session. We propose a novel algorithm for the circulation tree calculation, and then report on the implementation of this new solution.