Marta from the Stellar core team explains the Stellar Consensus Protocol, covering quorums, federated voting, the nomination protocol, and the ballot protocol. The talk uses simplified explanations and demos to help developers understand how SCP narrows down possible transaction sets until the network reaches agreement on a single value.
Marta, a software engineer on the Stellar core team, delivers a comprehensive educational talk on the Stellar Consensus Protocol (SCP). She covers quorum sets and thresholds, explaining how nodes trust each other and reach consensus. The talk introduces statements as the building blocks of SCP and explains federated voting rules: nodes vote for valid statements, accept when quorum slices or blocking sets agree, and confirm when all quorum slices accept. She demonstrates federated voting with a seven-node network example. The Stellar Consensus Protocol operates as a two-phase funnel: the nomination protocol selects multiple transaction sets to consider for a ledger, while the ballot protocol prepares and commits those values. A key invariant is that nodes stop voting for new nominations once they confirm their first one, ensuring eventual convergence. The ballot protocol runs optimistically while nomination continues in the background, allowing the network to reach consensus efficiently without waiting for nomination to complete.