In this paper, we present an effective overlay real-time video multicast system over the Internet. The proposed system effectively integrates overlay multicast technology and video compression technology. Overlay multicast tree and target bit rate are determined to satisfy the given average delay constraint, and H.263+ rate control is implemented to enhance the human visual perceptual quality over the multicast tree. Finally, experimental results are provided to show the performance of the proposed overlay video multicast system over the Internet.

In this paper, we propose a network-aware overlay multicast (NAOM) technique for large data dissemination in a well-managed overlay network. To improve the throughput, NAOM utilizes forward-only hosts; these hosts participate in the overlay network but are not members of the multicast. With the inclusion of the forward-only hosts, data slices can detour bottleneck links and more resources can be used to build efficient multicast trees. Large data are divided into fixed-size slices, and the slices are delivered simultaneously to multicast receivers along the multiple multicast trees. We model the problem of building efficient multicast trees with the inclusion of forward-only hosts. The problem is an NP-hard problem, and we introduce a polynomial time heuristic algorithm. Furthermore, we propose a dynamic scheduling scheme for the transfer of data along the evaluated multicast trees. Our experimental results in a real network environment show an improvement of the throughput but at the cost of additional resource consumption of forward-only nodes.

Multicast is an efficient transport mechanism for group-based community communications and mobile ad-hoc networks (MANET) is recently regarded as a promising solution for supporting ubiquitous computing as an underlying network technology. However, it is challenging to deploy the multicast mechanism used in a wired network directly into MANET owing to scarce resources in wireless networks and unpredictable changes in network topology. Several multicast mechanisms have been proposed in the literature to overcome these limitations. In MANET, especially, overlay multicasting schemes present several advantages over network-based multicasting schemes. However we have observed a common limitation of previously proposed overlay multicasting schemes. They introduce redundant data transmissions that waste network bandwidth and the battery of relay nodes. The observation motivated us to propose an efficient way to create and maintain a "semi-overlay structure" that utilizes a few nonmember nodes selected as branch nodes. The proposed scheme, called "SOMRP (Semi-overlay multicast routing protocol)," has been evaluated by using extensive network simulation in two different scenarios, comparing the performance of SOMRP with two previously proposed schemes. Simulation results show that SOMRP outperforms the two schemes in terms of the packet delivery ratio, transmission cost and end-to-end delay.

This paper presents an overlay multicast tree construction algorithm for synchronized realtime media multicast service over Internet which traditionally supports only best-effort service. The proposed tree construction algorithm is implemented to reduce not only the average delay of group members in order to support realtime media service, but also the delay variance among group members to provide an effective synchronized service. Basically, the orthogonal genetic algorithm is employed to obtain the near optimal tree among clusters with low computational complexity since the given problem is NP-complete. In addition, a dynamic tree maintenance process is proposed to effectively update the tree when members change due to leave or join. Finally, we describe experiments that show the superior performance of the proposed algorithm.

Overlay multicast schemes for Mobile Ad hoc Networks (MANET) [1] have been proposed to remove non group members' dependency for multicast forwarding. However, since all packets are relayed from one group member to other group member in a form of unicast packet, they sometimes cause a lot of packets' collision and low resource utilization particularly where group members densely locate. In this paper, we propose a new forwarding scheme, DESIRE (Density awarE heterogeneouS overlay multIcast foRwarding schemE in MANET), for overlay multicast in MANET. DESIRE is significantly different from previous overlay multicast schemes in that it creates separate data forwarding path over overlay DDT (Data Delivery Tree) depending on density of group members. In dense environment, a zone is constructed and a scoped flooding is applied within it. On the other hand, in sparse environment, data dissemination is accomplished in a form of unicast packet similar to previous overlay multicast. By adapting scoped flooding in dense environment, it can reduce a lot of packets' collision and balance battery consumption by making use of mobile node's broadcast capability entirely. Also, in sparse environment, DESIRE can cope with network mobility very well since overlay DDT can remain static regardless of changes in physical topology. Such distinct advantages are evaluated by simulation. Generally, better performance is shown with large group members than small group members.

One of the important problems in overlay multicast is how to deal with node failures and ungraceful leavings. When a non-leaf end host fails or leaves the multicast session, all downstream nodes will be affected. In this paper, we adopt the proactive approach, which pre-calculates a candidate node (called parent-to-be) for each node to connect to in case its current parent dies. The goal is to recover the overlay multicast tree quickly so that the disruption of service to those affected nodes is minimized. We combine the local parent-to-be locating and global parent-to-be locating schemes together, in order to take advantage of less interference in the local scheme and the flexibility of the global scheme. The quality of the recovered tree is improved while the responsiveness of the proactive approach is maintained.

In this letter, we propose to construct reliable overlay data delivery tree based on group member's packet loss rate while preserving end-to-end delay below predetermined threshold. Through practical simulation, performance is evaluated and compared.

To overcome inefficiencies on tree-based and mesh-based scheme, overlay multicast scheme for MANET has been recently proposed to provide higher packet delivery ratio than the former as well as more efficient resource usage than the latter. However, previous all overlay multicast schemes are not designed with any considerations for dense/sparse environments resulted from unlimited movement of mobile nodes. For this reason, all packets should be transmitted in the form of unicast packet so they cannot fully make use of node's broadcast capability even though some group members are densely distributed within single-hop on the same shared media. Due to above reason, this causes extra forwarding overhead, low resource utilization as well as high packet collision. In this paper, we propose a novel hybrid overlay multicast scheme, EAOM (Environment-Aware Overlay Multicast), which uses neighboring group members' information to deliver packet with low cost. In EAOM, a group member has two modes depending on the number of neighboring group members. Under dense environment, host group model in wired network is applied. While in sparse environment, packets are delivered to each receiver along overlay DDT (Data Delivery Tree) as same as previous overlay multicast schemes. Hence, EAOM can not only remove mentioned obstacles in dense environment, but also cope with network mobility very well in sparse environment. Using simulation results, we demonstrate that EAOM has good packet delivery ratio, low control overhead as well as short end-to-end delay.