The Research And Application Of Application Layer Multicast Reconstruction Technology

In recent years, with the development of the Internet, multicast technology is receiving increasing attention. Compared with unicast, multicast, which is a communication way of one point to many points, can save the bandwidth, lighten the network burden and improve the data transmission rate. Unlike traditional IP multicast, application layer multicast implements the multicast functionality at end hosts rather than routers, provides an inexpensive, deployable method of providing one-to-many communication and finds a solution to the problem of traditional IP multicast which hasn't been popularized for the reason of the market and the technology. However, end hosts are not stable and may leave the multicast tree or fail at any time. When a non-leaf end host leaves the multicast tree, all of this node's download nodes are affected. So, it is necessary to consider how to reconstruct the multicast tree after the node fails or leave the multicast tree in application layer multicast. Another neglected but equally important factor is the host of capacity constraints. If we do not consider the host's capacity constraints, it is possible to make a node to connect too many children nodes, this will lead to the result that the performance of the multicast tree as a whole will get poor dramatically.In order to reconstruct the multicast tree, a new application layer multicast algorithm with degree-constrained function is proposed. Using the available bandwidth, a function is defined to compute the connection capacity of the node. This application layer multicast algorithm tries to find a spanning tree for a number of nodes with a shortest tree diameter. Then, a proactive approach to reconstructing degree-constrained application layer multicast tree based on the minimum diameter tree is proposed. Its core thought is that each non-leaf node in the multicast tree computes previously a parent-to-be node for each of its children node before it fails or leaves, once the departure of the node really happen, all of its children can contact their respective parent-to-be node immediately.With C++ kit, we also develop a multicast communication prototype using the proposed algorithm. This communication prototype can construct multicast tree, detect the failure of the neighbors, reconstruct the multicast tree after some nodes fail or leave and transmit file by multicast. We do repeated tests in the local area network and have tested its performance.