| The current trend in network evolution is directed toward an end-to-end IP-based network, which combines mobility with multimedia-rich content. IP multicast can transmit the same information to several destinations, and avoid sending duplicated packets on the same link. Therefore, its inherent nature is to efficiently minimize the bandwidth required to deliver multimedia data to a large set of targeted receivers. With the rapid improvement in both wireless access technology and mobile communication, more and more mobile users will expect to have access to the services and applications available in traditional Internet, and these services will surely include multimedia applications. Consequently, many efforts are being made to provide efficient mobility and multicast support, and to bring the two together in the next generation of IP networks.Mobile IP is the proposed standard for IP mobility support and provides two schemes for mobile hosts to receive multicast data: bi-directional tunneling and remote subscription. In the former scheme, the home agent (HA) joins the multicast group on behalf of mobile hosts, and is responsible for forwarding multicast data to mobile hosts by the unicast tunneling. This scheme compromises the link sharing of IP multicast and uses sub-optimal routing. In the latter scheme, the mobile host joins the multicast group via a local multicast router on the foreign link being visit, thus enjoying the maximum advantage of link sharing in the multicast tree. However, it may incur frequent modifications of the multicast tree due to host mobility, and the tree maintenance overhead may compensate for bandwidth resource saved by IP multicast.This dissertation investigates major issues that influence the performance of mobile multicast routing protocol, and proposes several improved solutions by utilizing the ideas in the development of Mobile IP routing protocol. The main research work and contributions are as follows.(1) Based on the observation that the hierarchical mobility management model brings many benefits in handling unicast routing, a hierarchical mobile multicast routing protocol is proposed. In this scheme, the multicast agent is selected dynamically and can be located at any level in a hierarchical network of routers according to the handoff frequency of mobile hosts. Thus, it can offer the most efficient routing for the mobile hosts that reside at a network for a relatively long period of time, and avoid frequent tree reconstruction for the mobile hosts that perform handoff quickly. Actually, we find that remote subscription, bi-directional tunneling, which were proposed by the IETF (Internet Engineering Task Force) Mobile IP, and unicast mechanism are the special cases of hierarchical mobile multicast. In addition, we propose a smooth multicast agent handoff mechanism when mobile hosts cross different domains. This mechanism allows the multicast agent to forward multicast packets to the mobile host attached with access router that is geographically adjacent to access routers on the boundary of its domain. Thus, the previous multicast agent can continue serving the mobile host that just moves out of its domain, which minimizes the disruption of multicast service when a mobile host crosses domain boundaries.(2) According to host's moving status, two kinds of subscription are proposed. If mobile hosts perform handoff frequently, a domain root router-based subscription is used to hide host's micro mobility, and reduce the attained handoff frequencies. If mobile hosts move very slowly, a foreign agent-based subscription is used to offer the most efficient multicast data delivery. To support fast handoff, a domain root router maintains a new state--soft state. In such state, the domain root router does not provide multicast services for mobile hosts in its domain, but it still exchanges routing information with its parent node. If the handoff of a mobile host occurs, the domain root router in soft state can return to a multicast tree node quickly, and prepare multicast services for the mobile hosts.(3) In general, host's mobility can cause modification of the multicast tree. The purpose of reconstructing multicast tree is to remove triangular routing and offer optimal multicast delivery, but tree reconstruction also lays heavy load on the network since a lot of processing and transmitting overhead is produced. Therefore, we propose a mobile multicast routing protocol which differentiates node's state. According to the condition whether the multicast agent is forwarding multicast data or not, the idle state is distinguished from the active state. Since the multicast agent does not forward multicast data in idle state, we enlarge its service range to avoid unnecessary reconstruction. The multicast agent in active state will control its service range to trade off between the overhead of multicast data delivery and the overhead of tree maintenance. To reduce the disruption due to host's handoff, a previous subscription is proposed to resume multicast delivery from the previous multicast agent.(4) In the source specific multicast (SSM) model, the mobility of multicast sources will invalidate the source specific tree due to the reverse path forwarding (RPF) check failure. We propose a routing protocol for SSM source mobility on the basis of the hierarchical mobile management scheme, which provides a unified global architecture for both uni- and multicast routing in mobile IPv6 networks. The SSM channel is identified by the pair of the domain foreign agent IP address and multicast group address. Thus, the shortest delivery tree is rooted at the domain foreign agent. To ensure consistency at higher layers, the SSM session is announced by including the home address of the source, which is independent to the source's movement. If a source moves inside a domain, the SSM delivery tree will not be influenced. If the source enters into a new domain, it relies on the old delivery tree to inform the receivers to subscribe to the new channel on one hand, and to forward multicast data until no listeners exist on the other hand.(5) In a mobile environment, wireless links are error-prone and host's mobility may cause out-of-sync problem. We propose a domain-based multicast delivery to efficiently deal with the reliability issues in wireless networks. It uses a hierarchical architecture to deal with the problems of loss detection and loss recovery locally, which minimizes the impact on the multicast delivery tree. A domain root router (DRR) caches multicast packet until it is sure that all the mobile hosts (MHs) in the domain have received it. If the cache is going to overflow, the DRR demands acknowledgement for the first packets that are not acknowledged to improve cache's availability. When multiple MHs lose packets in a short period of time, the aggregated acknowledgement is generated to avoid ACK (acknowledgement) implosion. During host's handoff, the out-of-sync problem is solved by requesting the DRR to retransmit the missing packets through registration message.
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