The Byzantine Generals Problem：（拜占庭将军的问题）.pdfVIP

The Byzantine Generals Problem LESLIE LAMPORT, ROBERT SHOSTAK, and MARSHALL PEASE SRI International Reliable computer systems must handle malfunctioningcomponents that give conflicting information to different parts of the system. This situation can be expressed abstractly in terms of a group of generals of the Byzantine army camped with their troops around an enemy city. Communicatingonly by messenger, the generals must agree upon a common battle plan. However, one or more of them may be traitors who will try to confuse the others. The problem is to find an algorithm to ensure that the loyal generals will reach agreement. It is shown that, using only oral messages, this problem is solvable if and only if more than two-thirds of the generals are loyal; so a single traitor can confound two loyal generals. With unforgeable written messages, the problem is solvable for any number of generals and possible traitors. Applications of the solutions to reliable computer systems are then discussed. Categories and Subject Descriptors: C.2.4. [Computer-CommunicationNetworks]: Distributed Systems--network operating systems; D.4.4 [Operating Systems]: CommunicationsManagement-- network communication; D.4.5 [Operating Systems]: Reliability--fault tolerance General Terms: Algorithms, Reliability Additional Key Words and Phrases: Interactive consistency / 1. INTRODUCTION A reliable c o m p u t e r s y s t e m m u s t be able to cope with the failure of one or more of its c o m p o n e n t s . A failed c o m p o n e n t m a y exhibit a type of b e h a v i o r t h a t is often o v e r l o o k e d - - n a m e l y , s ending conflicting i n f o r m a t i o n to different parts of th e system. T h e p r o b l e m of coping with this type of failure