A router assisting control tree configuration mechanism for reliable multicast

For reliable multicast service, the mechanism based on hierarchical control tree can be a promising solution to avoid well-known feedback implosion. However, configuration of an efficient control tree is very difficult for IP Multicast because it does not provide explicit membership and routing topology information to upper layer protocol. If the transport layer tree and the network layer tree are very different, it may take large cost to handle control messages. Especially, when a node at a downstream link of the network routing tree becomes a parent node of an upstream link at the control tree of transport layer, the discrepancy between routing tree and control tree causes to waste network resources by redundant messages. This problem can be solved if router that knows the information on routing topology can support configuration of a control tree and reliable delivery. However, the change of router function embraces deployment problem. Thus, this paper proposed a very simple method of router assist to minimize change of router functions. With this method,routers are only required to recognize message types of control messages inorder to forward the messages to correct direction: upstream or downstream.