Unraveling Responsiveness of Chained BFT Consensus with Network Delay

TL;DR

This work analyzes the responsiveness of chained BFT consensus under network delay by developing a unified Markov Decision Process framework that encompasses CHS, 2CHS, and FHS. It introduces two information-theoretic metrics, chain growth $G(\alpha)$ and commitment rate $R(\alpha)$, and uses the MDP to derive optimal adversarial attack strategies under varying Byzantine fractions $\alpha$. Theoretical results show that increasing $\alpha$ degrades both metrics, while responsiveness helps primarily at low $\alpha$ with diminishing returns as $\alpha\to 1/3$, with FHS generally outperforming the others. The authors validate the theory with experiments on an extended Bamboo platform, confirming robustness to network delay fluctuations and providing practical guidance for designing more robust and efficient chained BFT protocols.

Abstract

With the advancement of blockchain technology, chained Byzantine Fault Tolerant (BFT) protocols have been increasingly adopted in practical systems, making their performance a crucial aspect of the study. In this paper, we introduce a unified framework utilizing Markov Decision Processes (MDP) to model and assess the performance of three prominent chained BFT protocols. Our framework effectively captures complex adversarial behaviors, focusing on two key performance metrics: chain growth and commitment rate. We implement the optimal attack strategies obtained from MDP analysis on an existing evaluation platform for chained BFT protocols and conduct extensive experiments under various settings to validate our theoretical results. Through rigorous theoretical analysis and thorough practical experiments, we provide an in-depth evaluation of chained BFT protocols under diverse attack scenarios, uncovering optimal attack strategies. Contrary to conventional belief, our findings reveal that while responsiveness can enhance performance, it is not universally beneficial across all scenarios. This work not only deepens our understanding of chained BFT protocols, but also offers valuable insights and analytical tools that can inform the design of more robust and efficient protocols.

Figures (6)

• Figure 1: An overview of the proposed framework.
• Figure 2: The consensus process of chained BFT protocols.
• Figure 3: The chain growth of 2CHS, CHS, and FHS.
• Figure 4: The commitment rate of 2CHS, CHS, and FHS.
• Figure 5: The commitment rate of CHS under our strategy, the baseline(simple strategy) and without attack.