A Reliable Multicast System for Shared Virtual Environment

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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