SNA: Current Requirements and Direction

Since its announcement in 1974, Systems Network Architecture (SNA) has evolved in terms of its functional content, configurational flexibility, and network management services. This paper briefly traces this progress to the present and examines the more recent advances in greater detail. It then discusses known requirements for enhanced application and transaction services, for additional provisions for very large networks , for continuing adaptation of small-system and transmission media advances, for inclusion of additional management capabilities, and for further integration of network standards-all of which will shape future SNA developments. A dozen years have passed since IBM introduced Systems Network Architecture (SNA) as the blueprint for the design of its communication products and for interconnecting them within networks. Introduced to meet an evident need for a long-term strategy for interconnecting disparate products, SNA has performed this role with notable success. This success can be measured by various indices: first, by the ever-growing number of SNA products of various manufacture and their enthusiastic acceptance in the marketplace; second, by the recognition in the industry of SNA as a pacesetter for functional richness and completeness; and third, by the facility of the architecture to meet new requirements and adapt to new technologies in an evolutionary fashion. An earlier paper' traced the early years in a comprehensive manner; here, after several years of additional developments, we again provide a checkpoint on the status of SNA and look at new requirements that will likely shape its future. In the next section, we review briefly the highlights of the evolution of SNA since its introduction. Then, in the ensuing sections, we discuss the recent advances in more detail, according to function. In each case, we examine trends and speculate on the future on the basis of new requirements for SNA. In 1974, SNA began as a simple tree-oriented, single-host network. Today, it has evolved to support multiple , independent, mesh-configured networks separately administered but interconnected by gateways into composite networks. End users can communicate freely with application programs anywhere in these composite networks without being aware of the network configurations. Some of the major highlights in the progress of SNA are shown in Figure 1. When SNA was introduced in 1974, it was supported by a single operating system (Disk Operating Sys-temlvirtual Storage, or DOS/VS) running on a single host connected to terminals through a front-end communication controller. At that time, the only SNA terminals available …