Reducing the costs of large-scale BFT replication
LADIS '08 Proceedings of the 2nd Workshop on Large-Scale Distributed Systems and Middleware
Journal of Parallel and Distributed Computing
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Fault tolerant distributed protocols typically utilize a ho- mogeneous fault model, either fail-crash or fail-Byzantine, where all processors are assumed to fail in the same man- ner. In practice, due to complexity and evolvability rea- sons, only a subset of the nodes can actually be designed to have a restricted, fail-crash failure mode, provided that they are free of design faults. Based on this consideration, we propose a fail-heterogeneous architectural model for dis- tributed systems which considers two classes of nodes: (a) full-fledged execution nodes, which can be fail-Byzantine, and (b) lightweight, validated coordination nodes, which can only be fail-crash. To illustrate the model we intro- duce HeterTrust as a practical trustworthy service replica- tion protocol. It has a low latency overhead, requires few execution nodes with diversified design, and prevents in- truded servers from disclosing confidential data. We also discuss applications of the model to DoS attacks mitigation and to group membership.