In this paper, we propose a new cell scheduling algorithm based on traffic characteristics for an input-queued ATM multicast switch. In many multicast switches, unicast service is supported as a subset of the multicast services. So, although there are some idle output ports after the multicast cell scheduling, some unicast packets cannot access the switch fabric because of well-known HOL blocking. To solve this problem, in a proposed cell scheduling algorithm, each input buffer is logically divided into two buffers. One is used for buffering the unicast packets and the other is used for buffering the multicast packets. At first, a string of one-bit tokens is passed around a ring through all input buffers which take high priority. And the string is also passed around a ring through all low priority input buffers. To determine the buffer which takes high priority in each input ports at each time slot, we proposed three cell scheduling algorithms. To increase the probability which a unicast input buffer reserves remaining idle output ports, we deploy window policy in all the unicast input buffers. So output port utilization can be maximized and mean packet delay can be minimized.
Through computer simulation, it can be seen that proposed scheme has lower mean packet delay than conventional scheduling algorithm. Moreover, proposed scheme does not only guarantee the throughput fairness among the input ports but also guarantee the throughput fairness between multicast packets and unicast packets.