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Autobahn: Seamless high speed BFT

Neil Giridharan, Florian Suri-Payer, Ittai Abraham, Lorenzo Alvisi, Natacha Crooks

Abstract

Today's practical, high performance Byzantine Fault Tolerant (BFT) consensus protocols operate in the partial synchrony model. However, existing protocols are inefficient when deployments are indeed partially synchronous. They deliver either low latency during fault-free, synchronous periods (good intervals) or robust recovery from events that interrupt progress (blips). At one end, traditional, view-based BFT protocols optimize for latency during good intervals, but, when blips occur, can suffer from performance degradation (hangovers) that can last beyond the return of a good interval. At the other end, modern DAG-based BFT protocols recover more gracefully from blips, but exhibit lackluster latency during good intervals. To close the gap, this work presents Autobahn, a novel high-throughput BFT protocol that offers both low latency and seamless recovery from blips. By combining a highly parallel asynchronous data dissemination layer with a low-latency, partially synchronous consensus mechanism, Autobahn (i) avoids the hangovers incurred by traditional BFT protocols and (ii) matches the throughput of state of the art DAG-based BFT protocols while cutting their latency in half, matching the latency of traditional BFT protocols.

Autobahn: Seamless high speed BFT

Abstract

Today's practical, high performance Byzantine Fault Tolerant (BFT) consensus protocols operate in the partial synchrony model. However, existing protocols are inefficient when deployments are indeed partially synchronous. They deliver either low latency during fault-free, synchronous periods (good intervals) or robust recovery from events that interrupt progress (blips). At one end, traditional, view-based BFT protocols optimize for latency during good intervals, but, when blips occur, can suffer from performance degradation (hangovers) that can last beyond the return of a good interval. At the other end, modern DAG-based BFT protocols recover more gracefully from blips, but exhibit lackluster latency during good intervals. To close the gap, this work presents Autobahn, a novel high-throughput BFT protocol that offers both low latency and seamless recovery from blips. By combining a highly parallel asynchronous data dissemination layer with a low-latency, partially synchronous consensus mechanism, Autobahn (i) avoids the hangovers incurred by traditional BFT protocols and (ii) matches the throughput of state of the art DAG-based BFT protocols while cutting their latency in half, matching the latency of traditional BFT protocols.
Paper Structure (34 sections, 18 theorems, 9 figures, 1 table, 2 algorithms)

This paper contains 34 sections, 18 theorems, 9 figures, 1 table, 2 algorithms.

Table of Contents

  1. Introduction
  2. Partial Synchrony: Theory meets Practice
  3. Hangovers & Seamlessness
  4. Existing Approaches
  5. Autobahn: Overview
  6. Model
  7. Autobahn: The Protocol
  8. Data dissemination
  9. From Lanes to Consensus
  10. Core consensus.
  11. Processing committed cuts.
  12. Governing Progress.
  13. View change
  14. Parallel Multi-Slot Agreement
  15. Optimizations
  16. ...and 19 more sections

Key Result

Lemma 1

If there exists a PrepareQC or CommitQC for consensus proposal $p$ in view $v$, then there cannot exist a PrepareQC or a CommitQC for consensus proposal $p'\neq p$ in view $v$.

Figures (9)

  • Figure 1: Latency Hangover in HotStuff yin2019hotstuff.
  • Figure 2: Car protocol pattern.
  • Figure 3: Autobahn parallel data lanes; example cut.
  • Figure 4: Core Consensus coordination pattern.
  • Figure 5: Throughput and Latency under increasing load.
  • ...and 4 more figures

Theorems & Definitions (20)

  • Definition 1
  • Definition 2
  • Lemma 1
  • Lemma 2
  • Lemma 3
  • Lemma 4
  • Theorem 1
  • Lemma 5
  • Lemma 6
  • Lemma 7
  • ...and 10 more