Adaptive tree-based recovery for scalable reliable multicast

As the scale of a network becomes larger in terms of both the number of users and geographic span, reliable multicast protocols suffer more severely from acknowledgement implosion and exposure to retransmissions. In this paper, we propose a scalable, efficient recovery scheme for a tree-based reliable multicast transport protocol. The scheme first constructs a logical tree of receivers as close to a multicast routing tree as possible by using error bitmap information. This ensures that the receivers residing at a higher level in a multicast routing tree than ones requesting retransmissions be appointed as parents in a corresponding logical tree. In our scheme, the logical tree is adaptively reconfigured as the session membership or the multicast route changes. Our scheme also forms local groups with separate multicast addresses in the tree for efficient recovery. We compare our scheme with a static tree-based reliable multicast protocol. Results of the simulation show that our adaptive tree-based recovery scheme outperforms the compared protocol in terms of the implosion and exposure as the session size increases.