A design and analysis of top-down based ACK-trees

For Reliable Multicast Service, to use a tree hierarchy can be a promising solution to avoid the well-known ACK-implosion. However, to build an efficient ACK-tree is very difficult for IP multicast because it does not provide explicit membership and routing topology information to the upper layer protocol. Due to the difficulties, not much study has been done on the control tree configuration yet, while it immensely affects the behavior and performance on a protocol using the mechanism. Previous approaches can be classified into top-down and bottom-up, and promising previous works have typically been focused on the bottom-up construction mechanism, because the top-down approach has some drawbacks like long tree creation time. However, the ERS-based mechanism, one of the representative bottom-up mechanisms, is known to cause heavy message overhead. Thus, we propose a novel method which takes the benefits of the top-down approach while relieving its most significant drawback, long tree creation time, adopting the concurrent tree creation concept from the bottom-up approach. We show the proposed mechanism reduces message overhead as well as builds a low level of tree. In addition, we achieve medium performance on tree creation time.