Trade-offs in large blockchain-based IoT system design

The well known Practical Byzantine Fault Tolerance (PBFT) consensus algorithm is not well suited to blockchain-based Internet of Things (IoT) systems which cover large geographical areas. To reduce queuing delays and eliminates a permanent leader as a single point of failure, we use a multiple entry, multi-tier PBFT architecture and investigate the distribution of orderers that will lead to minimization of the total delay from the reception of a block of IoT data to the moment it is linked to the global blockchain. Our results indicate that the total number of orderers for given system coverage and total load are main determinants of the block linking time. We show that, given the dimensions of an area and the number of orderers, partitioning the orderers into a smaller number of tiers with more clusters will lead to lower block linking time. These observations may be used in the process of planning and dimensioning of multi-tier cluster architectures for blockchain-enabled IoT systems.