Reliable Multicast Protocol with Packet Forwarding in Wireless Internet

One of the most important problems in reliable multicast communication is reducing generated redundant NAKs to avoid NAK implosion. A number of NAK suppression mechanisms which try to resolve this technical problem have been proposed thus far. In wireless multicast which includes mobile hosts with wireless access channel, packet losses occur because of not only low quality of wireless communication channel but also tentative shutdown of connection due to handover. When remote subscription which enables effective usage of network resources is applied, a host re-joins to a multicast group when handover occurs. This means handover will introduce long shutdown of connection, because not only handover process in layer 2 but also multicast join and multicast tree reconstruction is necessary. This causes loss of large amount of packets and finally causes NAK implosion. In this paper, we claim that packet forwarding which is originally applied to unicast communication can be applied to multicast communications and resolve this NAK implosion problem caused by handover. Our simulation results show that packet forwarding mechanism significantly improves scalability of NAK suppression-base reliable multicast protocol.