Research On Reliable Group Communication Based On Application-Layer Multicast

Nowadays, The are more and more applications that need reliable group communication service in Internet. Multicast is the most effective technology of group communication, so the research on its reliability becomes the focus. However the traditional IP multicast hasn't been widely deployed in Internet and the IP reliable multicast protocols are also puzzled by some problems. Thus the reliable group communication based on IP multicast technology currently can't satisfy the application requirement. The Application Layer Multicast (ALM) is an alternative of group communication as its feasibility and simpleness especially the convenience on resolving the problems of reliability. It has been a new approach to supply reliable group communication. But the existing reliable ALM protocols are deficient, especially on the scalability and the reliability of model.In the paper, a new scalabal and reliable ALM model—Mesh-Tree Hybrid Overlay Multicast (M-THOM) is proposed. The topology of the overlay is composed of mesh and tree, which can reduce the shortage of tree topology on reliability. The model adapts to the large scale group communication service that require severe reliability but isn't sensitive to delay. The main work is as the follows:1. IP reliable multicast and ALM are introduced, then some typical reliable ALM protocols and their characteristic on reliability are analyzed, accordingly the research motive and problems that need sovling are determined in this paper.2. According to the feature of mesh-first protocol and tree-first protocol, a new model M-THOM is proposed. It is composed of a core mesh and many attached trees. Then relevant mechanisms are also designed for ensuring the reliability of multicast, including the mechanism to establish and maintain the overlay, the mechanism to resiliently recover the overlay and the mechanism to ensure reliable data transmission.3. In the reliable data transmission mechanism, a distributed error control algorithm is designed. It is different from the traditional vertical recovery approach and uses a transverse backfence error recovery approach to enhance the recovery efficiency in the dynamic network. Additionally, the Congestion Control model for Overlay Multicast is improved to enhance the throughput of multicast.