874 research outputs found
Towards Optimal Synchronous Counting
Consider a complete communication network of nodes, where the nodes
receive a common clock pulse. We study the synchronous -counting problem:
given any starting state and up to faulty nodes with arbitrary behaviour,
the task is to eventually have all correct nodes counting modulo in
agreement. Thus, we are considering algorithms that are self-stabilizing
despite Byzantine failures. In this work, we give new algorithms for the
synchronous counting problem that (1) are deterministic, (2) have linear
stabilisation time in , (3) use a small number of states, and (4) achieve
almost-optimal resilience. Prior algorithms either resort to randomisation, use
a large number of states, or have poor resilience. In particular, we achieve an
exponential improvement in the space complexity of deterministic algorithms,
while still achieving linear stabilisation time and almost-linear resilience.Comment: 17 pages, 2 figure
Narwhal and Tusk: A DAG-based Mempool and Efficient BFT Consensus
We propose separating the task of reliable transaction dissemination from
transaction ordering, to enable high-performance Byzantine fault-tolerant
quorum-based consensus. We design and evaluate a mempool protocol, Narwhal,
specializing in high-throughput reliable dissemination and storage of causal
histories of transactions. Narwhal tolerates an asynchronous network and
maintains high performance despite failures. Narwhal is designed to easily
scale-out using multiple workers at each validator, and we demonstrate that
there is no foreseeable limit to the throughput we can achieve. Composing
Narwhal with a partially synchronous consensus protocol (Narwhal-HotStuff)
yields significantly better throughput even in the presence of faults or
intermittent loss of liveness due to asynchrony. However, loss of liveness can
result in higher latency. To achieve overall good performance when faults occur
we design Tusk, a zero-message overhead asynchronous consensus protocol, to
work with Narwhal. We demonstrate its high performance under a variety of
configurations and faults. As a summary of results, on a WAN, Narwhal-Hotstuff
achieves over 130,000 tx/sec at less than 2-sec latency compared with 1,800
tx/sec at 1-sec latency for Hotstuff. Additional workers increase throughput
linearly to 600,000 tx/sec without any latency increase. Tusk achieves 160,000
tx/sec with about 3 seconds latency. Under faults, both protocols maintain high
throughput, but Narwhal-HotStuff suffers from increased latency
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