Discusses how to replicate a server in order to obtainfault-tolerant services. In active replication, all the requests from aclient are performed by all the server replicas in the same order. Thereplicas are placed on heterogeneous computers interconnected in a widearea network, e.g. the Internet, where each communication channel has adifferent message transmission delay and bandwidth. Hence, the responsetimes of the replicas observed by the clients are not the same. Wepropose a pseudo-active replication, where the client does not wait forother responses after receiving one response, and slower replicas do notperform every request performed by the faster replicas
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