Consensus

Consensus guides the trust system and drives technology investment in blockchain application infrastructure, and therefore is at the heart of blockchain. Also, there isn't one consensus type that fits all use cases. Use cases define the interaction between participants and suggest a most appropriate trust system through consensus models.

Consensus is a way to validate the order of network requests or transactions (deploy and invoke) on a blockchain network. Ordering network transactions correctly is critical because many have a dependency on one or more prior transactions (account debits often have a dependency on prior credits, for example).

In a blockchain network, no single authority determines the transaction order; instead, each blockchain node (or peer) has an equal say in establishing the order, by implementing the network consensus protocol. Consensus consequently ensures that a quorum of nodes agree on the order in which transactions are appended to the shared ledger. Consensus, by resolving discrepancies in the proposed transaction order, helps guarantee that all network nodes are operating on an identical blockchain. In other words, it guarantees both the integrity and consistency of transactions in a blockchain network.