In a distributed system, we can state the assumptions we are making about the behavior (the system model) and design the actual system in such a way that it meets those assumptions. Algorithms can be proved to function correctly within a certain system model. This means that reliable behavior is achievable, even if the underlying system model provides very few guarantees. However, although it is possible to make software well behaved in an unreliable system model, it is not straightforward to do so.
