Decentralized Systems Engineering: Consensus and Fault Tolerance

Description

This lecture covers the fundamentals of decentralized systems engineering, focusing on consensus algorithms like Paxos and Multi-Paxos, as well as fault tolerance mechanisms. The instructor discusses key concepts such as logical clocks, Byzantine faults, and the Byzantine Generals Problem. The lecture also delves into Threshold Logical Clocks, fault-tolerant consensus, and the challenges of surviving faults in distributed systems. Additionally, the lecture explores the practical applications of fault-tolerant systems in real-world scenarios, such as network partitions and the importance of redundancy. The session concludes with an overview of permissionless consensus, blockchain structures, and key ideas behind Bitcoin, including Proof-of-Work and the assumptions underlying the Bitcoin protocol.

Official source

https://mediaspace.epfl.ch/media/0_8ga063ub

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Related lectures (38)

Related concepts (41)

Consensus (computer science)

A fundamental problem in distributed computing and multi-agent systems is to achieve overall system reliability in the presence of a number of faulty processes. This often requires coordinating processes to reach consensus, or agree on some data value that is needed during computation. Example applications of consensus include agreeing on what transactions to commit to a database in which order, state machine replication, and atomic broadcasts.

Fault tolerance

Fault tolerance is the property that enables a system to continue operating properly in the event of the failure of one or more faults within some of its components. If its operating quality decreases at all, the decrease is proportional to the severity of the failure, as compared to a naively designed system, in which even a small failure can cause total breakdown. Fault tolerance is particularly sought after in high-availability, mission-critical, or even life-critical systems.

Distributed ledger

A distributed ledger (also called a shared ledger or distributed ledger technology or DLT) is the consensus of replicated, shared, and synchronized digital data that is geographically spread (distributed) across many sites, countries, or institutions. In contrast to a centralized database, a distributed ledger does not require a central administrator, and consequently does not have a single (central) point-of-failure.

Decentralized autonomous organization

A decentralized autonomous organization (DAO), sometimes called a decentralized autonomous corporation (DAC), is an organization managed in whole or in part by decentralized computer program, with voting and finances handled through a blockchain. In general terms, DAOs are member-owned communities without centralized leadership. The precise legal status of this type of business organization is unclear. A well-known example, intended for venture capital funding, was The DAO, which amassed 3.

Paxos (computer science)

Paxos is a family of protocols for solving consensus in a network of unreliable or fallible processors. Consensus is the process of agreeing on one result among a group of participants. This problem becomes difficult when the participants or their communications may experience failures. Consensus protocols are the basis for the state machine replication approach to distributed computing, as suggested by Leslie Lamport and surveyed by Fred Schneider.