A Performance Analysis of BFT Consensus for Blockchains

TL;DR

This paper develops an analytical model to compare the performance of BFT consensus protocols Istanbul BFT and HotStuff in blockchain networks, considering network topology, timers, and fault tolerance.

Contribution

It introduces a closed-form analytical model for BFT protocols that accounts for network topology, timers, and crash faults, validated through simulations.

Findings

The model accurately predicts consensus time under various conditions.

Network topology significantly impacts protocol performance.

Proper timer setting is crucial for efficiency and progress.

Abstract

Distributed ledgers are common in the industry. Some of them can use blockchains as their underlying infrastructure. A blockchain requires participants to agree on its contents. This can be achieved via a consensus protocol, and several BFT (Byzantine Fault Tolerant) protocols have been proposed for this purpose. How do these protocols differ in performance? And how is this difference affected by the communication network? Moreover, such a protocol would need a timer to ensure progress, but how should the timer be set? This paper presents an analytical model to address these and related issues in the case of crash faults. Specifically, it focuses on two consensus protocols (Istanbul BFT and HotStuff) and two network topologies (Folded-Clos and Dragonfly). The model provides closed-form expressions for analyzing how the timer value and number of participants, faults and switches affect the consensus time. The formulas and analyses are validated with simulations. The conclusion offers some tips for analytical modeling of such protocols.