A Research On Hierarchical Domain Application Layer Multicast Method

Distributed application such as content distribution,remote education,video conference,on-line games calls a strong requirement for group communication technology. As a recommended solution, IP multicast is proposed early, but it has not been deployed on internet yet due to technical and commercial problems. Application layer multicast based on overlay networks is thought as a solution to provide group communication on internet, because of no need to change the under layer network structure,easy to be deployed and popularized.The existing application layer multicast overlay networks usually adopt periodic detection to get information about underlay network topology structure because of they assume it is random, or adopt structured P2P network based on distributed hash technology to simple protocol. Researches on network topology discovery and molding indicate the actual network has a loose hierarchical structure and small world effect. According to these considerations, an application layer multicast based on hierarchical domain is proposed in this paper, major content include the following two aspects:We analyze the limited situation of a simple application layer network mold using in centralized control when constructing an application layer multicast overlay network, then according to the results of topology discovery and molding and the aggregation property of IP assignment and routing, propose a hierarchical domain application layer network mold based on divide and conquer idea. A network hierarchical domain method using IP assignment information and regionalism is also proposed.Based on hierarchical domain mold, HDALM application layer multicast protocol is proposed. the node in HDALM adopts a up-down inter-hierarchy mapping and inner-domain requesting method to join a multicast group, uses bottom-up method to leave the multicast group, uses periodic message to maintain and optimize the group-shared multicast tree constructed, adopts a simple data forward arithmetic to deliver data to neighbors in each hierarchical domain. In simulation result and analysis, the average link stress and average path stretch is smaller, indicates a better data delivery path quality; the proportion of node that cat not receive data packet normal due to node failure is small and recovery time is short, indicates a strong failure recovery ability; control cost is small when group size increasing, indicates a good flexibility.