A Reliable Multicast System for Shared Virtual Environment

尽管多播通信作为能够有效地向大量人分发信息的技术而受到关注，但是在对等通信中开发的高可靠性技术或安全技术并不适用。特别地，我们开发了高信任组播技术，以实现真实的时间共享虚拟空间。我们提出的多播系统将用户划分为多个域，并在假设每个域的随机数产生机制和序列服务器的情况下，给出了消息的所有顺序和可靠性，在本研究中，当域的数量和消息速率信息的分布间隔改变时，通信延迟和额外消息的量进行了评估。结果表明，当引入域组合时，控制消息的数量减少，特别是分区的数量减少， ...更多信息 因此通信延迟减小。这取决于改变在域组成的影响下已经被分级的单个用户的传输速率。此外，仅向用于多播的特定成员传输信息的加密变得非常重要。为了更新对应于成员关系变化的密钥，需要一种有效的密钥传递方法。因此，我们提出了一个框架，使密钥在两个或两个以上的密钥分发服务器异步发布。然后，我们通过模拟评估。在密钥更新时系统不会停止，虽然同时管理两个或多个密钥会造成时间的浪费，但证实了密钥分发方法的有效性。最后，针对组播的重传处理，提出了只为重传处理做准备的节点称为重传服务器的方法。设计了转发服务器之间建立转发协作树的方法。特别地，它提出了当被称为备份链路的重传服务器之间的链路断开时准备替代链路的方法，并且能够提高重传树的可靠性。少

Although multicast communication is paid attention as a technology which can efficiently distribute information to the large number of people, the high-reliability technology or the security technology developed in the peer-to-peer communication are not applicable. Especially, we have developed the high trust multicast technology to share a virtual space in real time. The multicast system that we propose divides the user into some domains, and gives the all order of the message and reliability on the assumption of the random numbers generation mechanism and the sequence server of each domain.In this research, the amount of a communication delay and extra messages were evaluated, when the number of domains and the interval for distribution of information on the message rate were changed. It turned out the same number of clients that the number of control messages decreased when the domain composition was introduced and the situation, especially the number of partitions was reduced, and … More the communication delay decreased as a result. This depends on change the transmission rate of an individual user having been leveled in the effect of the domain compositionMoreover, the encryption to transmit information only to a specific member for the multicast becomes very important. To renew the key corresponding to the change of membership, the efficient method of delivering a key is needed. Therefore, we proposed the framework to make the key asynchronously issued in two or more key distribution servers. Then, we evaluated it by the simulation. There was no system stop when the key was renewed, and it was confirmed that the method of key distribution was efficient though time when two or more keys were managed at the same time was caused.Finally, it proposed the method of preparing the node only for the processing of retransmission which was called a retransmission server about the processing of retransmission of the multicast. The method of constructing the tree to make between retransmission servers which were called a tree of retransmission cooperate was designed. Especially, it proposed the method of preparing an alternative link when the link between retransmission servers that were called a backup link was disconnected, and the reliability of the retransmission tree was able to be improved. Less