Multistage network having multicast routing congestion feedback

Multicasting of an ingress cell received at one of a plurality of input ports is provided through a multistage network to a plurality of output ports. The received ingress cell at a first input port includes a data payload and information identifying one or more routing queues to which a single copy of the data payload is to be outputted. A backpressure queue assignment is identified for the first ingress cell, the backpressure queue assignment identifying a backpressure indicator indicative of the congestion level at at least one routing queue of a subsequent stage. Using the backpressure indicator, it is determined if the first ingress cell is to be outputted from one or more of the routing queues. Thereafter, the first ingress cell is outputted from one or more of the routing queues when the congestion level is below or equal to a first threshold.