BackPackers: A New Network Paradigm for Secure and High-performance Blockchains

Despite many scaling proposals for Bitcoin protocols, existing permissionless approaches, including BitcoinCompact, Bitcoin-NG, and Conflux, achieve very low efficiency in terms of networking. In our large-scale peer-to-peer blockchain simulation, no existing permissionless protocols can achieve more than 4% bandwidth utilization, the fraction of bandwidth used for transmitting confirmed transactions. We propose BackPackers, a cross-layer paradigm that optimize concurrently both consensus (layer 1) and network communication (layer 0) protocols. BackPackers introduces a new node role, called packers, who form a secure and decentralized network backbone. Without any trust assumption, independent packers work together to effectively distribute transactions to all miners, eliminating a major network bottleneck in broadcasting transactions. In exchange for their networking service, each packer receives a portion of transaction fees that it distributes. Through theoretical analysis, we show rigorous proofs for security properties, namely, consistency and liveness. Most importantly, we prove that BackPackers achieves (1− )-optimality in throughput, with respect to the network limit, and O(1)-optimality in block propagation time, even when the network is heterogeneous. Through experimental studies, we show that BackPackers can achieve up to 80% bandwidth utilization, achieving 8,000+ tps and 1.2s block propagation time for 1,000 nodes with 20Mbps bandwidth. Under a same networking condition, BackPackers achieves an order of magnitude higher throughput comparing to the state-of-the-arts permissionless blockchains.