Practical Byzantine Reliable Broadcast on Partially Connected Networks (Extended version)

TL;DR

Byzantine Reliable Broadcast in partially connected networks is addressed by integrating Bracha's asynchronous BRB with Dolev's RC, under the standard $f < \frac{N}{3}$ and $2f+1$ connectivity assumptions. The authors extend Dolev’s optimizations to the BRB setting and introduce 12 cross-layer modifications (MBD.1–MBD.12) within a BDopt protocol stack that supports repeatable broadcasts via $(s, bid)$. Through real deployments and extensive simulations, they demonstrate substantial latency and bandwidth reductions, and they provide guidance on combining modifications to suit varying network asynchrony, connectivity, and payload sizes. A reference implementation is released to facilitate adoption and further improvements in practice.

Abstract

In this paper, we consider the Byzantine reliable broadcast problem on authenticated and partially connected networks. The state-of-the-art method to solve this problem consists in combining two algorithms from the literature. Handling asynchrony and faulty senders is typically done thanks to Gabriel Bracha's authenticated double-echo broadcast protocol, which assumes an asynchronous fully connected network. Danny Dolev's algorithm can then be used to provide reliable communications between processes in the global fault model, where up to f processes among N can be faulty in a communication network that is at least 2f+1-connected. Following recent works that showed that Dolev's protocol can be made more practical thanks to several optimizations, we show that the state-of-the-art methods to solve our problem can be optimized thanks to layer-specific and cross-layer optimizations. Our simulations with the Omnet++ network simulator show that these optimizations can be efficiently combined to decrease the total amount of information transmitted or the protocol's latency (e.g., respectively, -25% and -50% with a 16B payload, N=31 and f=4) compared to the state-of-the-art combination of Bracha's and Dolev's protocols.

Figures (10)

• Figure 1: A communication graph with $N{=}10$ nodes and a node connectivity $k{=}3$. Any two nodes are either directly connected, or connected through 3 vertex-disjoint paths.
• Figure 2: Composition of Bracha's and Dolev's algorithms to implement BRB on partially connected networks.
• Figure 3: Interfaces in a cross-layer combination of Bracha's and Dolev's protocols to implement BRB on partially connected networks.
• Figure 4: Modifications MBD.1, 7, 8, 9, 11 - $N{=}50, f{=}9$, 1024 B payload.
• Figure 5: Configuration - $(N,f)\!=\!(50,10)$, 1024 B payload.