AADL is an architecture description language intended for model-based engineering of high-integrity systems. The AADL Behavior Annex is an extension allowing the refinement of behavioral aspects described through AADL. When implementing Distributed Real-time Embedded system, fault tolerance concerns are integrated by applying replication patterns. We considered a simplified design of the primary backup replication pattern to express the modeling capabilities of AADL and its annex. Our contribution intends to give accurate description of the synchronization mechanisms integrated in this example.