| With the rapid progress in wireless network technology and popularization of mobile devices in recent years, mobile users expect to access Internet whenever they have time and wherever they may be. Therefore, providing the mobility of support is the inevitable trend of Internet. It is imperative to determine the best way to provide better services to mobile equipments. In the meantime, with the continual increasing of multicast applications, as well as more users involved, IP multicast has become an important subject in both research and development. As IP multicast naturally has the merit of high scalability and efficiency, which is more significant for mobile environments, more and more people pay attention to these two techniques, and many efforts are being made to bring them together (i.e., mobile multicast).In this dissertation, the basic concepts and work principle of Mobile IPv4, Mobile IPv6 and IP multicast are introduced, the challenges which exist in mobile multicast are analyzed in detail, and the evaluation criteria of mobile multicast algorithms and protocols are summarized. Two basic mobile multicast schemes, i.e., Bi-directional Tunnel (BT) and Remote Subscription (RS) defined in both Mobile IPv4 and Mobile IPv6, and their improved version for mobile multicast algorithms and protocols are introduced. Based on these works, the advantages and application situations of these algorithms or protocols are discussed respectively, also the shortcomings and problems are analysed in depth, and then a comprehensive comparison is given.The dissertation investigates mobile multicast algorithms and protocols in IPv6 networks and major issues that influence the performance of mobile multicast routing protocols. The main research work and contributions are as follows.(1)Based on dynamic multicast agent approach, a novel mobile multicast protocol named TD-DMAMoM (Time and Distance-aided Dynamic Multicast Agent-based Mobile Multicast protocol) was proposed. In TD-DMAMoM, the dynamic selection of multicast agent is based on the metrics of time and distance. On one hand, the number of binding update messages (BUs) issued by each mobile node of the local network is recorded and the statistical average is calculated by the subnet multicast agent. If there is mobile node(s) with more BUs than the statistical average, the metric of time is set to be the logical value of "True". Meanwhile, the distance (measured in hops) between mobile node and multicast agent, the minimum distance between mobile node and multicast forwarding tree are calculated, respectively. These two values are compared and used to set the logical value of metric of distance, i.e., "True" or "False". Only when the metrics of both time and distance are "True", the changing of multicast agent will then be launched. Simulation results show that TD-DMAMoM has advantages such as avoiding the frequently reconstructing of multicast delivery tree effectively and decreasing multicast handover delay significantly, resulting in near-optimal multicast forwarding path and capability of integration with the existing network protocols, i.e., being of great practicality.(2) An implementation of multiple home agents mechanism for mobile multicast, i.e., MHAsMoM (Multiple Home Agents for Mobile Multicast) was proposed in this paper, to address the problem of home agent as a single point of failure in mobile multicast. In MHAsMoM, the problem of home registration among multiple home agents is solved. Meanwhile, a novel application-layer anycast algorithm is adopted in our proposed scheme, by means of which a "nearest" home agent from multiple home agents can be selected in the home network for mobile multicast receivers. MHAsMoM is able not only to solve the problem due to home agent as a central point of failure, but also to provide better anycast resolution service. |
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