  Synchronous computation models simplify the design and the verification of
fault-tolerant distributed systems. For efficiency reasons such systems are
designed and implemented using an asynchronous semantics. In this paper, we
bridge the gap between these two worlds. We introduce a (synchronous)
round-based computational model and we prove a reduction for a class of
asynchronous protocols to our new model. The reduction is based on properties
of the code that can be checked with sequential methods. We apply the reduction
to state machine replication systems, such as, Paxos, Zab, and Viewstamped
Replication.
