Elastic multicast: Design extensions and experimentation results

This paper describes a new implementation of the Elastic Multicast (EM) protocol including new design enhancements for improved dynamic operation. The paper also presents additional performance data collected from emulation-based mobile network experiments. EM is a low complexity extension to Simplified Multicast Forwarding (SMF) that adds group-specific dynamic pruning of the SMF-based multicast forwarding mesh for higher rate traffic flows. It therefore reduces overhead by pruning the SMF relay sets in areas where no receivers exist. Our experimental emulation results show that, under a variety of mobility conditions and multicast group distribution patterns, EM maintains SMF-like data delivery robustness while significantly reducing overhead. We also demonstrate that a new design feature that provides preemptive ACK messages for active receiver groups leads to lower loss under mobility and sparse receiver groups. Based upon the results, we consider this feature critical to be included in any future EM design. We also present experimental results examining the performance of EM with classical flooding (CF) and connected dominating set (CDS) relay modes. We show, for the experiments examined, that CF provides some reduced loss with minimal additional overhead when used with EM. We also discuss future work and ongoing issues.