Fault tolerance is a design principle of industrial systems, or of industrial _automated_ systems. Byzantine Fault Tolerance (BFT) specifically enables them to function correctly and reach consensus even in the presence of faulty or malicious components. In a Byzantine fault-tolerant system, nodes can communicate and exchange information, but some of them may exhibit arbitrary and potentially malicious behavior, such as sending contradictory messages or withholding information. Practical Byzantine Fault Tolerance (PBFT) is a specific algorithm that achieves Byzantine fault tolerance in distributed systems. It was introduced by Miguel Castro and Barbara Liskov in 1999. PBFT is designed to provide a high degree of fault tolerance while maintaining low latency and high throughput. It is commonly used in permissioned blockchain networks where a known set of nodes participate in the consensus process. PBFT is often considered one of the options for permissioned blockchains, not really suitable for decentralized blockchain networks. The major design flaw is its assumption of a known and fixed set of nodes. A degree of trust is assumed among the participating nodes which are typically known entities. The consensus algorithm is designed to ensure that even if some nodes behave maliciously or fail, the correct nodes can still reach agreement on the state of the system. Nodes communicate with each other to reach a consensus on the order and validity of transactions. Through a series of rounds, a leader node is selected to propose a block of transactions. The other nodes then validate the proposed block and send their votes to the network. Once a sufficient number of votes are received, the block is considered committed and added to the blockchain. However, PBFT assumes a partial synchrony model, where the network eventually becomes synchronous and messages are delivered within a certain time frame. If the network experiences long delays or becomes highly asynchronous, performance and fault tolerance guarantees may degrade. Blockchains do use variants of Practical Byzantine Fault Tolerance (PBFT) consensus algorithms. Here are a couple examples: 1. Hyperledger Fabric: Hyperledger Fabric is an open-source blockchain platform that utilizes PBFT consensus. It is designed for enterprise use cases and offers a modular architecture, allowing organizations to build and deploy their own blockchain networks. You can find more information about PBFT in Hyperledger Fabric's documentation: https://sawtooth.hyperledger.org/docs/1.2/pbft/using-pbft-consensus.html 2. Tendermint: Tendermint is a Byzantine Fault Tolerant (BFT) consensus engine that employs a variant of PBFT. It is used as the consensus mechanism in various blockchain projects, including Cosmos Network. Tendermint's documentation provides detailed information on its PBFT-based consensus algorithm: https://docs.tendermint.com/v0.34/introduction/what-is-tendermint.html#consensus-overview