Dumbo-NG: Fast Asynchronous BFT Consensus with Throughput-Oblivious Latency

TL;DR

Dumbo-NG introduces a novel asynchronous BFT consensus protocol that achieves high throughput and low latency by enabling concurrent transaction dissemination and agreement, while also ensuring censorship resilience without extra costs.

Contribution

The paper presents Dumbo-NG, a new asynchronous BFT consensus protocol that reduces the throughput-latency trade-off and guarantees censorship resilience through a novel reduction to multi-valued validated Byzantine agreement.

Findings

Dumbo-NG achieves higher peak throughput than existing protocols.

Latency remains nearly stable as throughput increases.

Dumbo-NG effectively prevents censorship without additional costs.

Abstract

Despite recent progresses of practical asynchronous Byzantine fault tolerant (BFT) consensus, the state-of-the-art designs still suffer from suboptimal performance. Particularly, to obtain maximum throughput, most existing protocols with guaranteed linear amortized communication complexity require each participating node to broadcast a huge batch of transactions, which dramatically sacrifices latency. Worse still, the f slowest nodes' broadcasts might never be agreed to output and thus can be censored (where f is the number of faults). Implementable mitigation to the threat either uses computationally costly threshold encryption or incurs communication blow-up, thus causing further efficiency issues. We present Dumbo-NG, a novel asynchronous BFT consensus (atomic broadcast) to solve the remaining practical issues. Its technical core is a non-trivial direct reduction from asynchronous atomic broadcast to multi-valued validated Byzantine agreement (MVBA) with quality property. Most interestingly, the new protocol structure empowers completely concurrent execution of transaction dissemination and asynchronous agreement. This brings about two benefits: (i) the throughput-latency tension is resolved to approach peak throughput with minimal increase in latency; (ii) the transactions broadcasted by any honest node can be agreed to output, thus conquering the censorship threat with no extra cost. We implement Dumbo-NG and compare it to the state-of-the-art asynchronous BFT with guaranteed censorship resilience including Dumbo (CCS'20) and Speeding-Dumbo (NDSS'22). We also apply the techniques from Speeding-Dumbo to DispersedLedger (NSDI'22) and obtain an improved variant of DispersedLedger called sDumbo-DL for comprehensive comparison. Extensive experiments reveal: Dumbo-NG realizes better peak throughput performance and its latency can almost remain stable when throughput grows.