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Back in the mid-1970s, IBM introduced its host-based Systems Network Architecture (SNA), which was later enhanced by cross-domain SNA Network Interconnection (SNI) and decentralized Advanced Peer-to-Peer Networking (APPN) functions. In the early 1980s, IBM also introduced NetBIOS (Network Basic Input/Output System), a communication technology originally targeted at local area networks (LANs), and started offering support for the Transmission Control Protocol/Internet Protocol (TCP/IP) family and the Open Systems Interconnection (OSI) architecture to address multivendor network environments. This broad palette of network offerings raises sometimes difficult selection and compatibility issues for users of IBM products. To address user requirements and support IBM's commitment to open networking, a research project discussed in this paper sets forth a model pulling the above protocols together into one integrated architectural framework that provides a rich, but flexible, modular and uniform set of functions across all system(1) platforms and all network types.
This paper presents a general model for the integrated architecture and then focuses on the technical details of the SNA-OSI case. The paper is organized into six sections and a summary: The first section presents the motivations and objectives of the project; the second section lists the technical requirements that must be met; the third section positions the effort with respect to prior attempts at relating the SNA and OSI architectures; the fourth section stresses the basic approach of the integration project and underlines its key features; the fifth section then outlines the overall design for the resulting integrated system structure; the final section discusses in more detail one selected and particularly important aspect of the design, the integration of SNA and OSI naming, addressing, and internetwork routing mechanisms.
MOTIVATIONS AND OBJECTIVES
The early releases of SNA enabled a host computer to communicate first with a hierarchical network of communication controllers and device control units, then with terminals and printers attached to that network. This basic architecture was later enhanced to allow two or more hosts to communicate with one another and with terminals and printers via a meshed network of communication and device controllers.(2) Then SNI allowed several such meshed SNA networks to be interconnected into essentially unlimited internetworks.(3) Most recently, the APPN architecture(4,5) was defined to support networks of minicomputers and personal workstations, without requiring the centralized...