Age-aware Fairness in Blockchain Transaction Ordering

In blockchain applications, transaction latency is crucial for determining the quality of service (QoS). Transaction latency is measured as the time between its issuance and its inclusion in a block in the chain. When different applications use the same blockchain network, a block proposer often prioritizes its own application transactions over other applications transactions to minimize its own latency. To maintain fairness, a block proposer is typically supposed to select the included transactions randomly providing each transaction similar chances to be included. The random selection might cause some transactions to experience high latency since this selection implies a high variance in the time a transaction waits until it is selected. We suggest an alternative, age-aware approach towards fairness so that transaction priority is increased upon observing a large waiting time. The challenge with this approach is that the age of a transaction is not absolute due to transaction propagation. Moreover, a node might present its transactions as older to obtain priority. We consider three network restrictions on transaction propagation and explain how to enhance fairness in each one of them. We describe three declaration schemes in which a node declares its pending transactions providing the ability to validate transaction age. We demonstrate the advantages of the solutions on Ethereum and synthetic data in reducing tail latency. Stand up in the presence of the aged Leviticus 19:32