Critical causality in istributed virtual environments

We investigate the causality issue in distributed virtual environments. Causality has been widely studied in parallel and distributed systems. However, most of the work in causality detection and preservation are from a logical time system point of view, which are not generally suitable for distributed virtual environments due to the high cost of the proposed schemes to preserve causality. In this paper, first, critical causal order is defined, which is a relaxation of the "happened before"-based causal relation. Then, causal receive order delivery is proposed with the advantage that both the real-time property of distributed virtual environments and the critical causal order relationship among events are preserved. Finally, an algorithm to achieve causal receive order delivery is given. Our algorithm is easy to implement, and it results in little extra traffic on the network.