| As a feasible substitute of IP multicast in network level, application level multicast (ALM) gets more and more attention. Based on the present research results in the related fields, different kinds of ALM schemes are analyzed. And then, their advantages and disadvantages are given out respectively. To deal with the disadvantages and to make the scheme suitable for the situation that different end hosts in the real network have different bandwidth, a Priority-based Hierarchical ALM scheme, called PH-ALM, is proposed.Besides keeping other advantages of the hierarchical ALM scheme, PH-ALM can balance the distribution of data transmission load, adapt to the environment that the end hosts'bandwidth are variety, and improve the flexibility of ALM tree construction scheme. PH-ALM introduces the notion of Priority to be the metric during the process of ALM tree construction. Both the end-to-end delay and the bandwidth capacity of the nodes in the multicast group are considered. Like classic hierarchical ALM scheme, PH-ALM divides the group members into different clusters, which then will form into different levels. Then, for each cluster, PH-ALM will build an inner-cluster Minimum Overall Latency Spanning Tree, which is an important feature of PH-ALM. Thereby, the ALM tree can be flexibly built and adapt to the environment that the end hosts'bandwidth are variety. In addition, there are periodical optimization algorithms to optimize the structure of inner-cluster ALM tree. This optimization process is a local operation, so it can keep the system stability well.The well-known tool OPNET modeler is used to prove the feasibility of PH-ALM. Comparing with classic ALM schemes, the conclusion can be drawn that, PH-ALM has improved performance in average end-to-end delay, link resource usage, data transmission load balance, failure recovery latency, stability, etc. So we can draw the conclusion that under the circumstances that end hosts have different bandwidths, PH-ALM is feasible. |
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