Finding Nemo-Nemo: CFT DAG-based Consensus in the WAN

TL;DR

Nemo-Nemo is a novel crash-fault tolerant consensus protocol using a DAG structure, achieving high throughput and low latency in wide-area networks by combining design principles from CFT and BFT systems.

Contribution

It introduces a DAG-based CFT consensus protocol with multi-leader architecture and deferred leader proposals, outperforming existing protocols in WAN environments.

Findings

Nemo-Nemo commits on a DAG in just two network hops.

It achieves higher throughput than existing CFT protocols.

It maintains performance under challenging network conditions.

Abstract

This paper introduces Nemo-Nemo, a practical crash-fault tolerant (CFT) consensus protocol designed to outperform existing protocols in wide-area networks by bridging design principles from the CFT and Byzantine-fault tolerant (BFT) worlds. By structuring command propagation through a causally ordered DAG, Nemo-Nemo allows all consensus replicas to propose commands with a naturally self-regulating communication regime. By exploiting multi-leader architecture, Nemo-Nemo avoids the performance bottleneck inherent to single-leader protocols. By separating command dissemination from consensus logic, Nemo-Nemo handles challenging network conditions even when consensus commits are stalled. Moreover, leader proposals that miss a deadline are never dropped, but deterministically deferred and executed later, preserving throughput under transient network delays. And by enabling Nemo-Nemo to commit on a DAG in just two network hops, it matches the latency of existing CFT systems, while achieving significantly higher throughput. The result is a robust, deployable system: the first DAG-based CFT consensus protocol proven to exceed state-of-the-art wide-area network performance in both speed and resilience.