Causal Order, Logical Clocks, State Machine Replication
Keywords and Synonyms
State-machine replication: active replication
This entry covers several problems, related with each other. The first problem is concerned with maintaining the causal relationship between events in a distributed system. The motivation is to allow distributed systems to reason about time with no explicit access to a physical clock. Lamport  defines a notion of logical clocks that can be used to generate timestamps that are consistent with causal relationships (in a conservative sense). He illustrates logical clocks (also called Lamport clocks) with a distributed mutual exclusion algorithm. The algorithm turns out to be an illustration of state-machine replication. Basically, the algorithm generates a total ordering of the events that is consistent across processes. With all processes starting in the same state, they evolve consistently with no need for further synchronization.
The system consists of a collection of...
- 1.Défago, X., Schiper, A., Urbán, P.: Total order broadcast and multicast algorithms: Taxonomy and survey. ACM Comput. Surv. 36, 372–421 (2004)Google Scholar
- 2.Fidge, C. J.: Logical time in distributed computing systems. IEEE Comput. 24, 28–33 (1991)Google Scholar
- 3.Lamport, L.: On interprocess communication. Part I: Basic formalism. Distrib. Comput. 1, 77–85 (1986)Google Scholar
- 6.Mattern, F.: Virtual time and global states of distributed systems. In: Cosnard, M., Quinton, P. (eds.) Parallel and Distributed Algorithms, pp.215–226. North-Holland, Amsterdam (1989)Google Scholar
- 7.Raynal, M., Singhal, M.: Capturing causality in distributed systems. IEEE Comput. 29, 49–56 (1996)Google Scholar
- 8.Schneider, F.B.: Implementing fault-tolerant services using the state machine approach: a tutorial. ACM Comput. Surv. 22, 299–319 (1990)Google Scholar