This is a great article on the boundaries between cloud and fog computing from an application perspective! In fact, the concept of fog computing was introduced by Cisco.
When networks of the dot-com era were fast becoming obsolete, Cisco had to embrace the cloud age to survive and expand. With their huge leverage of the deployed Cisco base, their renewed effort was to extend the cloud to the edge of the enterprise to facilitate the connectivity and operation of networking services between the network edge (close to end users) and cloud computing. The term "fog" or "edge" was coined during this effort.