The applications layer, the topmost in the seven-layer ISO/OSI systems interconnect model as well as the topmost in the book’s five-layer model, is by far the hottest topic in the LAN industry. This layer is the final frontier, the one where users get full use of a network and within which they can construct the future distributed processing products. Simple products such as file transfer protocols, virtual terminal protocols, message handling systems, transaction processing, job transfer and manipulation, remote databases access, and remote procedure call mechanisms are coming into being—as well as more advanced products that are built on top of these services. The applications layer and the user applications applied to it provide the framework to build onto truly integrated environments.