The ULTRIX Implementation of DECnet/OSI

1 Abstract The DECnet/OSI for ULTRIX software was developed to allow the ULTRIX operating system and ULTRIX workstation software systems to operate in a multivendor, multiprotocol network based on open standards. It operates in a complex networking environment that includes OSI, DECnet Phase IV, X.25, and TCP/IP protocols. BSD sockets and protocol switch tables provide the entry points that define interfaces for protocol modules. The DECnet /OSI for ULTRIX software incorporates Digital's Enterprise Management Architecture, which provides a framework on which to consistently manage the various components of a distributed system. The DECnet/OSI for ULTRIX software provides a set of powerful tools and a system that can be extended to include new functions as they are incorporated in the OSI standard. DECnet/OSI for ULTRIX is an end system implementation that supports the open systems interconnection (OSI) protocol through the Digital Networking Architecture (DNA) Phase V software. This implementation provides several features and programming environments that are consistent with the UNIX system philosophy of networking. Ease of use, extensibility, and portability were key design goals during product development. Operation of DECnet/OSI for ULTRIX software in a complex networking environment provides coexistence and interaction with the transmission control protocol/internet protocol (TCP/IP), DECnet Phase IV, X.25, and multivendor OSI networks. The paper "Overview of Digital's Open Networking" (in this issue) provides a suitable introduction to DECnet/OSI concepts.[1] For more details concerning standard Berkeley Software Distribution (BSD) networking concepts, the reader is referred to the general references listed at the end of this paper. This paper provides an overview of DECnet/OSI for ULTRIX software. It discusses some of the design decisions made during product development, including the use of protocol switch tables. It describes the system's five communication domains, emphasizing the X.25, data link, and OSI domains. The paper continues with a discussion of application programming interfaces, interfaces into kernel modules, and a network management interface established for extensibility. It concludes with a description of network management and network configuration.