Using NIC-Based Multicast Scheme to Improve Forwarding Rate for Application Layer Multicast

Recently, application layer multicast (ALM) has become an effective alternative to IP multicast across the Internet. By deeply analyzing the characteristics of traditional packet forwarding in end host, this paper proposes a high performance multicast scheme, in which a NIC-based multicast mechanism is used to send multiple replicas of a ALM packet to different destinations with less CPU intermediation compared to the traditional host- based multicast scheme. By adopting the NIC-based multicast scheme, the CPU overhead and the number of times data packets are copied from host memory to NIC buffer are reduced. Theoretical analysis indicates that the new scheme can notably decrease the multicast delay and enhance the service capability of ALM proxies. We have modified the NIC driver and added some corresponding APIs to network protocol stack in order to implement the proposed scheme. Experimental results illustrate that the NIC-based multicast scheme can greatly improve forwarding rate for ALM.