Application Layer Multicast in P2P Distributed Interactive Applications

By sharing resources among peers in peer-to-peer network, application layer multicast (ALM) has been shown an efficient way to improve the scalability and reduce the latency of communication. To deploy ALM in peer-to-peer distributed interactive applications (DIAs), the property of many-to-many communication of DIA demands multiple multicast trees to be constructed in the overlay. Therefore, how to efficiently allocate resources among multiple trees to maximize the benefit is an important and challenging issue. In this paper, we study the problem of building ALM trees with minimum total end-to-end delay to receivers in peer-to-peer DIAs with resource constraints on network bandwidth. The end-to-end delay from a sender to receivers in a multicast tree consists of the link delay as well as the packet queuing delay at intermediate peers, while the latter is often ignored or not well studied in the previous work. In this paper, we explicitly establish the relationship between the queuing delay at peers and the topology of multicast trees in peer-to-peer DIAs. Based on the relationship, the above mentioned problem is defined and we prove that it is NP-complete. We present a centralized heuristic algorithm to obtain an approximate solution. Moreover, distributed algorithms are also investigated to refine the topology in practical systems with dynamic changes. Extensive experiments were conducted by simulations to evaluate the proposed algorithms and results are reported in the paper.