Optimistic Generic Broadcast

Atomic Broadcast, used for example in state machine replication, requires three communication steps. Optimistic Atomic Broadcast requires only two steps if all processes receive messages in the same order. Generic Broadcast requires two steps if no messages conflict. We present an algorithm that subsumes both of these approaches and guarantees two-step delivery if all conflicting messages are received in the same order, and three-step delivery otherwise. Internally, our protocol uses two new algorithms. First, a Consensus algorithm which, in runs without failures, decides in one communication step if all proposals are the same, and needs two steps otherwise. Second, a method that allows us to run infinitely many instances of a distributed algorithm, provided that at most finitely many of them are different.

• Type: Conference
• Year: 2005
• Where: WDAG
• Authors: Piotr Zielinski
• Keywords: Algorithms, Atomic Broadcast, Communication Step, Optimistic Atomic Broadcast, WDAG 2005