A method and apparatus are provided for scheduling unicast and multicast
data in an input-queued network device. According to one aspect of the
present invention, a combined schedule is created by pipelined staging of
multicast and unicast scheduling. Multicast cells are scheduled for
transmission among multiple interfaces of a crossbar by performing a
multicast cell scheduling cycle for multiple classes of service that are
supported by the network device. Then, unicast cells are scheduled for
transmission among the interfaces at a lower priority than the previously
scheduled multicast cells by performing a unicast cell scheduling cycle
for the multiple classes of service using only those interfaces that
remain unmatched after completion of the multicast cell scheduling cycle.