Mobility Tolerant Adaptive Multicast Protocols for Ad Hoc Networks

由通过无线电信道通信的移动的主机组成的移动的自组织网络正越来越多地用于局域网、执法、军事行动和无数其他应用。 这些应用程序中的大多数（如果不是全部的话）涉及从一个主机（源）向指定的主机组发送消息，并且对于各种应用程序，网络中可能存在大量这样的组。 多播涉及向受限的进程组发送消息，并且形成了在分布式系统上有效实现基于组的应用的基础。 许多用于在静态网络中有效地执行多播的协议是可用的，而此时，在设计用于自组织网络的这种协议中的许多关键技术问题仍然没有解决，包括对功率限制和高速数据问题的优雅解决方案，在由于主机移动性和包含任何拓扑变化的影响的能力而导致的过渡期间，确保消息无损的有效方法在附近 在移动的ad hoc网络中，网络的拓扑随着节点移动、无线电传播条件的变化以及节点的电池功率的耗尽而改变。 拓扑变化的速率在不同的时间以及网络的不同区域可以是不同的。 网络可能经历频繁的网络划分，并且可能需要重新配置划分的子网络。 拟议的研究将采取理论和实验相结合的方法，并将其应用到新兴的分布式应用程序。 在这项建议中，研究人员结合专业知识在网络中的基于组的通信和稳定的协议在异步分布式计算系统的领域提出了一个创新的综合研究项目，在容错多播协议设计的移动的ad hoc网络。 所提出的设计旨在展示各种令人印象深刻的好处，包括：（1）该协议将支持可变速率的混合流量，具有通过动态链路成本估计器（取决于信道带宽，应用程序的服务质量（QoS），主机的电池电量等）快速适应流量突然变化的能力。 (2)该协议是自稳定的，任何拓扑结构的变化，由于节点的移动将触发协议和最优的组播树将是新的拓扑结构和快速重建。 (3)自稳定协议被增强了保证服务保持可用的特征，同时多播树被适配于新拓扑（即，在恢复周期期间存在于系统中的多播消息不会丢失）。(4)该协议的自稳定功能是以受控的方式触发的，以便通过使用有效的故障遏制策略，在存在高流动性的情况下不会压倒系统。(5)该研究旨在开发一种新的执行模型的自稳定算法在分布式系统的基础上，在现实生活中的条件下的ad hoc网络，而不是传统的对抗性预言模型，这样的算法。 研究人员预计，这将导致使用的概念，自我稳定，以解决其他真实的生活问题，涉及恢复从一个短暂的行为。 用于在具有上述益处的移动的自组织网络中执行多播的有效解决方案将依赖于底层数据链路层可以提供什么样的支持以及网络层多播协议可以如何利用这些设施来智能地控制开销，同时提供期望的QoS。 这项建议将采取协同的方法设计多播协议，使它们与基本的网络层兼容。 所开发的协议将通过模拟进行广泛的评估。 此外，一个原型协议栈将实现在IEEE 802.11 MAC层的顶部，以评估在QoS的改善，分布式媒体分发和协作应用。

Mobile ad hoc networks consisting of mobile hosts that communicate via wireless radio channels are being increasingly used for local area networks, law enforcement, military operations and myriad of other applications. Most of these applications, if not all, involves sending messages from one host (source) to a specified group of hosts and there can be a large number of such groups in the network for diverse kinds of applications. Multi-cast involves sending messages to a restricted group of processes and forms the basis for efficient implementation of group based applications on a distributed system. Many protocolsfor efficiently performing multi-cast in static networks are available while at this time, a number of critical technical issues in designing such protocols for ad hoc networks remain unresolved, including elegant solutions to issues of power limitations and high speed data, effective methods of assurance for losslessness of the messages during transition period due to host mobility and the ability to contain the effect of any topology change locally. In mobile ad hoc networks the topology of the network changes with node movements, variations in the radio propagation conditions, and depletion of battery power of the nodes. The rate of topological changes can be different at different times, as well as in different regions of the network. The network can experience frequent network partitioning and may require reconfiguration of the partitioned subnetworks. The proposed research will take a combined theoretical and experimental approach and will apply this to emerging distributed applications. In this proposal the researchers with combined expertise in the fields of group based communications in networks and stabilization of protocols in asynchronous distributed computing systems are proposing an innovative integrated research project in fault-tolerant multi-cast protocol design for mobile ad hoc networks. The proposed design intends to demonstrate a variety of impressive benefits including: (1) The protocol will support mixed traffic of variable rates with the ability to adapt fast with ease to sudden changes in traffic via a dynamic link cost estimator (that depends on channel bandwidth, quality-of-service (QoS) to the applications, battery power of the hosts, etc.) (2) The protocol is self-stabilizing in that any topological change due to mobility of nodes will trigger the protocol and the optimal multicast tree will be for the new topology and quickly reconstructed. (3) The self-stabilizing protocols are augmented with features that guarantees that the service remains available while the multi-cast tree is being adapted to the new topology (i.e., multicast messages present in the system during the recovery period are not lost). (4) The self-stabilization features of the protocol are triggered in a controlled manner so as to not overwhelm the system in presence of high mobility by using efficient fault-containment strategies. (5) The research intends to develop a new execution model for the self-stabilizing algorithms in a distributed system based on the real-life conditions of an ad hoc network as opposed to the traditional adversarial oracle model for such algorithms. The researchers expect that this will lead to the use of the concept of self-stabilization to solving other real life problems involving recovery from a transient behavior. Efficient solutions for performing multi-casting in mobile ad hoc networks with the above benefits will rely on what support underlying data link layer can provide and how the network layer multi-cast protocol can exploit these facilities to intelligently control the overheads while providing desirable QoS. This proposal will take a synergistic approach in designing the multi-cast protocols so as to make them compatible with the underlying networking layers. The developed protocols will be extensivaly evaluated through simulation. Further a prototype protocol stack will be implemented on the top of IEEE 802.11 MAC layer to evaluate the improvement in QoS to distributed media distribution and collaboration applications.