The Collaborative Virtual Environment (CVE) is a computer mediated virtual environment that is shared by geographically separated users. Participants communicate, interact, and collaborate with each other in a CVE. The characteristics of an ideal CVE that fosters efficient collaboration among its users include the awareness, the consistency, and the responsiveness.
Most of previous CVE systems use pessimistic concurrency control methods to guarantee some level of weak consistency, and have long response time. Optimistic concurrency methods can achieve short response time but none of the previous CVE systems used them. We propose an optimistic ordering method for the CVE. Our method can simplify finding inter object dependencies by using effective space.
Network communications on the CVE require reliable multicast communications and short latency. This thesis proposes Fast Recovery Reliable Multicast Protocol (FRM) for CVE to satisfy these requirements. In contrast to many reliable multicast protocols that use suppression timers to avoid ACK/NAK implosion, the FRM does not use suppression timers. Instead, the FRM uses local request and local recovery techniques to obtain fast recovery. Our techniques take advantage of network topology to avoid NAK implosion problem.
