Houtan Aghili

Atomic Broadcast

In distributed systems subject to random communication delays and component failures, atomic broadcast can be used to implement the abstraction of synchronous replicated storage, a distributed storage that displays the same contents at every correct processor as of any clock time. This paper presents a systematic derivation of a family of atomic broadcast protocols that are tolerant of increasingly general failure classes: omission failures, timing failures, and authentication-detectable Byzantine failures. The protocols work for arbitrary point-to-point network topologies, and can tolerate any number of link and process failures up to network partitioning. After proving their correctness, we also prove two lower bounds that show that the protocols provide in many cases the best possible termination times.

Atomic broadcast in a real-time environment

This paper presents a model for real-time distributed systems that is intermediate in complexity between the simple, perfectly synchronous model in which there are rounds of communication exchange among processors in a completely connected network and an asynchronous model in which there is no reasonable upper bound on the time required for transmission and processing of messages. In this model algorithms are described for atomic broadcast that can be used to update synchronous replicated storage, a distributed storage that displays the same contents at every correct processor as of any clock time. The algorithms are all based on a simple communication paradigm and differ only in the additional checking required to tolerate different classes of failures.