Aggregated Multicast - A Comparative Study

Multicast state scalability is among the critical issues which delay the deployment of IP multicast. In our previous work, we proposed a scheme, called aggregated multicast to reduce multicast state. The key idea is that multiple groups are forced to share a single delivery tree. We presented some initial results to show that multicast state can be reduced. In this paper, we develop a more quantitative assessment of the cost/benefit trade-offs. We introduce metrics to measure multicast state and tree management overhead for multicast schemes. We then compare aggregated multicast with conventional multicast schemes, such as source specific tree scheme and shared tree scheme. Our extensive simulations show that aggregated multicast can achieve significant routing state and tree management overhead reduction while containing the expense of extra resources (bandwidth waste and tunnelling overhead, etc.). We conclude that aggregated multicast is a very cost-effective and promising direction for scalable transit domain multicast provisioning.