An Ack-tree Creation Mechanism Using Top-down Scheme for Tree-based Reliable Multicast Transport Protocols

To meet the requirements of various applications such as software distributions, shared text editors, etc., reliable transmission should be guaranteed over IP Multicast where only best-effort service is supported. Among the current researches, hierarchical tree-based mechanism has been proposed and actively studied. This mechanism is known to provide high scalability, but needs to build an efficient logical ACK-tree in transport layer. Many studies have been made, and bottom-up approach has been mainly used. This approach has benefits from parallel tree construction for receivers, while it brings large message overhead. Therefore, this paper proposes a top-down based mechanism which reduce the message overhead during tree creating process and can simply guarantee loop-freeness by step-wise mannered tree building. Through experimental simulations, it shows that the proposed mechanism has less message overhead, while the bottom-up scheme has better performance on tree configuration time in a large session. So, it is recommended that the top-down and bottom-up schemes will be selectively used in the real world, according to the requirements of the concerned multicast applications.