Abstract:

Blockchain relies on an unstructured Peer-to-Peer （P2P） overlay network for the propagation of transactions and blocks. In this network structure， propagation is delayed， and the long-tail propagation problem is significant， which lead to inconsistencies in the information stored by nodes， that is the phenomenon of blockchain forks. Forks not only waste computational resources in the entire blockchain network， but also introduce a series of security issues. To reduce propagation delays in blockchain networks， a Neighbor Selection scheme based on Multi-stage Propagation （NSMP） was proposed to optimize the network topology by selecting neighbor nodes. Firstly， the nodes’ Outbound neighbors were divided into strong and weak propagators based on two factors： propagation ability and proximity， and different neighbor selection schemes were applied at different stages of network propagation， thereby reducing propagation hops and shortening propagation time. At the same time， the long-tail propagation problems in both existing and default schemes were further solved. Finally， the propagation ability of nodes was quantified by a fitting function based on node local characteristics， proximity information of the nodes was quantified using the Ping protocol， and the designed scheme was tested through simulation experiments using the network simulator SimBlock. Experimental results show that NSMP reduces the fork rate by 52.17% compared to the default scheme， demonstrating the feasibility and effectiveness of NSMP. Besides， according to the simulation data of experiments， the optimal parameter setting for the distribution of neighbor node proximity was determined.

Key words: block chain, Peer-to-Peer (P2P) network, fork, propagation delay, neighbor selection

摘要：

区块链基于非结构化的点对点（P2P）覆盖网络传播交易和区块。在这种网络结构上，传播具有延迟性且传播的长尾问题显著，而这些会导致节点存储信息的不一致，即区块链的分叉现象。分叉不仅浪费了整个区块链网络的算力资源，还带来了一系列的安全问题。为了减少区块链网络的传播延迟，提出一种基于多阶段传播的邻居选择方案（NSMP），通过邻居节点的选择优化网络拓扑结构。首先，根据传播能力和邻近度两个因素，将节点Outbound邻居分为强传播和弱传播两部分，并针对网络传播的不同阶段应用不同的邻居选择方案，从而减少传播跳跃和缩短传播时间；并且，进一步解决现有方案和默认方案都存在的传播长尾问题；最后，根据节点局部特征的拟合函数量化节点的传播能力，通过Ping协议量化节点的邻近度信息，并使用网络模拟器SimBlock对设计的方案进行模拟实验。实验结果表明，NSMP比默认方案的分叉率降低了52.17%，验证了NSMP的可行性和有效性。此外，根据实验模拟数据，确定了邻居节点邻近度远近分配的最佳参数设置。

关键词: 区块链, 点对点网络, 分叉, 传播延迟, 邻居选择