Efficient and Reliable Application Layer Multicast for Flash Dissemination

To disseminate messages from a single source to a large number of targeted receivers, a natural approach is the tree-based application layer multicast (ALM). In time-constrained flash dissemination scenarios, e.g. earthquake early warning, where time is of the essence, the reliable extensions of the tree-based ALM using ack-based failure recovery protocols cannot support reliable dissemination in the timeframe needed. In this paper, we propose FaReCast which exploits path diversity, i.e., exploit the use of multiple data paths, to achieve fast and reliable data dissemination. First, we design a forest-based M2M (Multiple parents-To-Multiple children) ALM structure where every node has multiple children and multiple parents. The intuition is to enable lower dissemination latency through multiple children, while enabling higher reliability through multiple parents. In order to maintain the M2M ALM structure in a scalable and reliable manner, we develop a DHT-based Distributed Configuration Manager. Second, we design multidirectional multicasting algorithms that effectively utilize the multiple data paths in the M2M ALM structure. A key aspect of our reliable dissemination mechanism is that nodes, in addition to communicating the data to children, also selectively disseminate the data to parents and siblings. As compared to trees using traditional multicasting algorithm, we observe an 80 percent improvement in reliability under 20 percent of failed nodes with no significant increase in latency for over 99 percent of the nodes. Moreover, we notice that FaReCast can reduce the network overhead more than 50 percent by tuning the M2M structure, as compared to the other reliable ALM based disseminations.