Summary of L6: Byzantine Fault Tolerance

00:00:00 - 00:25:00

Byzantine fault tolerance is a technique used in distributed systems to survive failures. The technique is based on the assumption that an adversary can attack the system in various ways, and that communication time between nodes is bounded. The Byzantine fault-tolerance protocol is designed to ensure that two armies in a distributed system are always in agreement about what to do. If one of the generals is lost, the protocol is not able to solve the problem and an inconsistent state persists.

• 00:00:00 Byzantine fault tolerance is a technique used in distributed systems in order to survive failures. The assumption made is that an adversary can attack the system in various ways and that communication time between nodes is bounded.
• 00:05:00 The Byzantine fault-tolerance protocol outlined in the video is designed to ensure two armies in a distributed system are always in agreement about what to do. The protocol uses a series of messages to ensure that both generals are always in agreement. If one of the generals is lost, the protocol is not able to solve the problem and an inconsistent state persists.
• 00:10:00 The Byzantine generals problem is a problem in distributed systems where different generals must agree on a decision. It was first published in 1982.
• 00:15:00 The Byzantine generals problem is a problem in which five generals must agree on a single order, but can't because one or more of them is a traitor. The problem can be solved by using a solution to the problem where one third or more of the generals are traitors. If this solution is used to solve the one trader three generals case, then it can be said that the problem is impossible to solve.
• 00:20:00 The "Oral Messages Algorithm" is a solution to the Byzantine generals problem, which states that if one-third or more of a commander's subordinates are traitors, the loyal generals will not be able to agree on an order. The algorithm works by sending orders only to those lieutenants who have been told the order by the commander.
• 00:25:00 This YouTube video provides a brief introduction to Byzantine fault tolerance, a problem that can be expensive to solve. The video explains that, in general, Byzantine fault tolerance is an expensive task to complete, and suggests that, before attempting to solve the problem, users consider whether they really need to do so. It also provides a brief explanation of the Byzantine generals problem and some of the follow-on papers that have been written on the topic.