Research On Model And Protocol Of ALM-based Survivable Group Communication

With the development of Internet, new applications make steadily increasing needs for multicast technology, such as video-conferencing, distributed simulations, multi-party games, content distribution, video streaming distribution, etc. For these needs, IP multicast was proposed by S.Deering in 1988, but due to a variety of technical and non-technical reasons, IP multicast has not been widely deployed in Internet. Then the Application Layer Multicast (ALM) was proposed. It can overcome many shortcomings of IP multicast because of its flexibility in deployment and implement. At present, as network scale increasingly grow up, group communication systems are often confronted with various attacks and threats. In this case, how to improve group communication systems survivability becomes current hotspot. Aiming at this problem, ALM survivability was introduced by researchers. Its main idea is to ensure group communication systems to accomplish critical services while some overlay nodes/links are disabled.Currently, ALM overlay has such limitations in topology: mesh overlay can provide preferable survivability and small routing delay, but its scalability is pool, so it can not be used in large-scale group communications. Despite tree overlay has advantages in bandwidth usage and routing delay, but it has limitations in structure, it is difficult to provide survivability. Ring overlay is immune to single node/link failure by means of bidirectional link list, but it has not provided suitable solutions to many nodes/links failure, and it has large routing delay.To solve the problems of the existing schemes, a survivable group communication scheme based on hierarchical ring topology is proposed, including the model design and the description of Survivable Hierarchical Ring Protocol (SHRP). The main idea is that we construct a hierarchical ring overlay, which covers all the members in the group, and then managing the members by layers and clusters. The overlay survivability is improved by means of spare ring, successor list and secondary leader node. At last, the simulation of SHRP shows that this scheme has preferable survivability, scalability and routing delay.