【Author】
Huang, Huawei; Yue, Zhengyu; Peng, Xiaowen; He, Liuding; Chen, Wuhui; Dai, Hong-Ning; Zheng, Zibin; Guo, Song
【Source】IEEE TRANSACTIONS ON PARALLEL AND DISTRIBUTED SYSTEMS
【Abstract】This article studies the PBFT-based sharded permissioned blockchain, which executes in either a local datacenter or a rented cloud platform. In such permissioned blockchain, the transaction (TX) assignment strategy could be malicious such that the network shards may possibly receive imbalanced transactions or even bursty-TX injection attacks. An imbalanced transaction assignment brings serious threats to the stability of the sharded blockchain. A stable sharded blockchain can ensure that each shard processes the arrived transactions timely. Since the system stability is closely related to the blockchain throughput, how to maintain a stable sharded blockchain becomes a challenge. To depict the transaction processing in each network shard, we adopt the Lyapunov Optimization framework. Exploiting drift-plus-penalty (DPP) technique, we then propose an adaptive resource-allocation algorithm, which can yield the near-optimal solution for each network shard while the shard queues can also be stably maintained. We also rigorously analyze the theoretical boundaries of both the system objective and the queue length of shards. The numerical results show that the proposed algorithm can achieve a better balance between resource consumption and queue stability than other baselines. We particularly evaluate two representative cases of bursty-TX injection attacks, i.e., the continued attacks against all network shards and the drastic attacks against a single network shard. The evaluation results show that the DPP-based algorithm can well alleviate the imbalanced TX assignment, and simultaneously maintain high throughput while consuming fewer resources than other baselines.
【Keywords】Blockchains; Protocols; Stability analysis; Throughput; Numerical stability; Bitcoin; Scalability; System stability; sharded blockchain; queueing theory; imbalanced transaction assignment
【标题】基于分片的许可区块链中针对不平衡交易分配的弹性资源分配
【摘要】本文研究了基于PBFT的分片许可区块链，它要么在本地数据中心执行，要么在租用的云平台上执行。在这种允许的区块链中，事务(TX)分配策略可能是恶意的，使得网络碎片可能接收不平衡的事务或者甚至突发TX注入攻击。不平衡的事务分配给分裂的区块链带来了严重的威胁。一个稳定的分片区块链可以保证每个分片及时处理到达的事务。由于系统稳定性与区块链吞吐量密切相关，如何保持稳定的分片区块链成为一个挑战。为了描述每个网络分片中的事务处理，我们采用了李亚普诺夫优化框架。利用漂移加惩罚(DPP)技术，我们提出了一种自适应的资源分配算法，该算法可以为每个网络分片提供接近最优的解，同时分片队列也可以稳定地保持。我们还严格分析了系统目标和分片排队长度的理论界限。数值结果表明，与其他基线相比，该算法能在资源消耗和队列稳定性之间取得更好的平衡。我们特别评估了bursty-TX注入攻击的两个典型案例，即针对所有网络碎片的持续攻击和针对单个网络碎片的猛烈攻击。评估结果表明，与其他基线相比，基于DPP的算法能够很好地缓解不均衡的TX分配，同时保持较高的吞吐量，同时消耗较少的资源。
【关键词】区块链；协议；稳定性分析；吞吐量；数值稳定性；比特币；可扩展性；系统稳定性；分片区块链；排队论；不平衡的交易分配
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