@inproceedings{BergerReiserSousaetal.2019, author = {Berger, Christian and Reiser, Hans P. and Sousa, Jo{\~a}o and Bessani, Alysson}, title = {Resilient Wide-Area Byzantine Consensus Using Adaptive Weighted Replication}, series = {38th IEEE International Symposium on Reliable Distributed Systems (SRDS 2019)}, booktitle = {38th IEEE International Symposium on Reliable Distributed Systems (SRDS 2019)}, publisher = {IEEE Xplore}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:739-opus4-7537}, pages = {10 Seiten}, year = {2019}, abstract = {In geo-replicated systems, the heterogeneous latencies of connections between replicas limit the system's ability to achieve fast consensus. State machine replication (SMR) protocols can be refined for their deployment in wide-area networks by using a weighting scheme for active replication that employs additional replicas and assigns higher voting power to faster replicas. Utilizing more variability in quorum formation allows replicas to swifter proceed to subsequent protocol stages, thus decreasing consensus latency. However, if network conditions vary during the system's lifespan or faults occur, the system needs a solution to autonomously adjust to new conditions. We incorporate the idea of self-optimization into geographically distributed, weighted replication by introducing AWARE, an automated and dynamic voting weight tuning and leader positioning scheme. AWARE measures replica-replica latencies and uses a prediction model, thriving to minimize the system's consensus latency. In experiments using different Amazon EC2 regions, AWARE dynamically optimizes consensus latency by self-reliantly finding a fast weight configuration yielding latency gains observed by clients located across the globe.}, language = {en} } @inproceedings{BergerReiser2018, author = {Berger, Christian and Reiser, Hans P.}, title = {Scaling Byzantine Consensus: A Broad Analysis}, series = {SERIAL'18 Proceedings of the 2nd Workshop on Scalable and Resilient Infrastructures for Distributed Ledgers}, booktitle = {SERIAL'18 Proceedings of the 2nd Workshop on Scalable and Resilient Infrastructures for Distributed Ledgers}, publisher = {ACM}, address = {New York, NY, USA}, isbn = {978-1-4503-6110-1}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:739-opus4-7526}, pages = {6 Seiten}, year = {2018}, abstract = {Blockchains and distributed ledger technology (DLT) that rely on Proof-of-Work (PoW) typically show limited performance. Several recent approaches incorporate Byzantine fault-tolerant (BFT) consensus protocols in their DLT design as Byzantine consensus allows for increased performance and energy efficiency, as well as it offers proven liveness and safety properties. While there has been a broad variety of research on BFT consensus protocols over the last decades, those protocols were originally not intended to scale for a large number of nodes. Thus, the quest for scalable BFT consensus was initiated with the emerging research interest in DLT. In this paper, we first provide a broad analysis of various optimization techniques and approaches used in recent protocols to scale Byzantine consensus for large environments such as BFT blockchain infrastructures. We then present an overview of both efforts and assumptions made by existing protocols and compare their solutions.}, language = {en} } @inproceedings{BergerRodriguesReiseretal.2024, author = {Berger, Christian and Rodrigues, L{\´i}vio and Reiser, Hans P. and Cogo, Vin{\´i}cius and Bessani, Alysson}, title = {Chasing lightspeed consensus}, series = {Middleware '24: Proceedings of the 25th International Middleware Conference}, volume = {2024}, booktitle = {Middleware '24: Proceedings of the 25th International Middleware Conference}, publisher = {ACM}, address = {New York}, isbn = {979-8-4007-0623-3}, doi = {10.1145/3652892.3700756}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:739-opus4-19106}, pages = {158 -- 171}, year = {2024}, abstract = {Blockchain technology sparked renewed interest in planetary-scale Byzantine fault-tolerant (BFT) state machine replication (SMR). While recent works predominantly focused on improving the scalability and throughput of these protocols, few of them addressed latency. We present Mercury, a novel transformation to autonomously optimize the latency of quorum-based BFT consensus. Mercury employs a dual resilience threshold that enables faster transaction ordering when the system contains few faulty replicas. Mercury allows forming compact quorums that substantially accelerate consensus using a smaller resilience threshold. Nevertheless, Mercury upholds standard SMR safety and liveness guarantees with optimal resilience, thanks to its judicious use of a dual operation mode and BFT forensics techniques. Our experiments spread tens of replicas across continents and reveal that Mercury can order transactions with finality in less than 0.4s, half the time of a PBFT-like protocol (optimal in terms of number of communication steps and resilience) in the same network. Furthermore, Mercury matches the latency of running its base protocol on theoretically optimal internet links (transmitting at 67\% of the speed of light).}, language = {en} }