Sender-initiated Configuration of an ACK-Tree for Reliable Multicast Transport

Tree-based ACK mechanism for reliable multicast service is well -known to provide high scalabil ity as well as reliability. However, it should be followed an eff icient ACK-Tree construction mechanism. The ERS(Expanding Ring Search) mechanism which is a receiver-driven bottom-up approach has been mainly used to construct an ACK-tree. However, it is known to cause heavy message overhead and to have possibili ty to cause loop during tree creation process. In the other hand, top-down approach can guarantee loop-free tree, but it cannot provide concurrent tree creation, so it takes long time to create an ACK-tree. This paper proposes a loop-free ACK-tree creation mechanism that supports semi-concurrent tree creation using sender-initiated approach. In addition, this paper proposes a tree reconfiguration method which can lessen unbalanced and abnormal tree shape which may caused by dynamic group join and leave.