Improving Bitcoin's Resilience to Churn

Efficient and reliable block propagation on the Bitcoin network is vital for ensuring the scalability of this peer-to-peer network. To this end, several schemes have been proposed over the last few years to speed up the block propagation, most notably the compact block protocol (BIP 152). Despite this, we show experimental evidence that nodes that have recently joined the network may need about ten days until this protocol becomes 90% effective. This problem is endemic for nodes that do not have persistent network connectivity. We propose to mitigate this ineffectiveness by maintaining mempool synchronization among Bitcoin nodes. For this purpose, we design and implement into Bitcoin a new prioritized data synchronization protocol, called FalafelSync. Our experiments show that FalafelSync helps intermittently connected nodes to maintain better consistency with more stable nodes, thereby showing promise for improving block propagation in the broader network. In the process, we have also developed an effective logging mechanism for bitcoin nodes which we release for public use.