Exploiting Overlay Path-Diversity for Scalable Reliable Multicast

IP-multicast is a bandwidth efficient transmission mechanism for multimedia communication. Reliability in IP-multicast, however, remains a significant challenge. This paper addresses the reliability and scalability issues in IP-multicast by exploring a novel, highly distributed overlay peer-to-peer retransmission architecture that exploits path-diversity. A simple unicast-based "tracert" tool is proposed to help to identify peers with disjoint path to the sender as potential retransmission nodes. Probing can help to adapt to the dynamics of the network. We show that a hybrid system with both "tracert" and probing can perform better than probing only or "tracert" only approach. In addition, we identify the proper probing interval that does not introduce significant probing overhead yet can collect sufficiently updated information to help recover most of the lost packets. The proposed hybrid multicast system is practical, scalable, and easy to deploy, requiring no change to the existing network infrastructure.