The purpose of this book is twofold: to introduce the user to the open systems interconnection (OSI) model and to relate the Digital Network Architecture at Phase V to that model. The book achieves both purposes by a combination of a high-level survey and lower-level detail in a top-down exposition that utilizes a side-by-side comparison of OSI services and DECnet services. This book has value both as a survey and as a pointer to more detailed references; it does not suffice as a designer’s or user’s guide.

The book consists of five parts: “The Digital Network Architecture,” “DNA Functional Layers,” “Network Applications,” “Related Architectures and Mechanisms,” and “Data Link Layer Protocols.” It also contains a list of acronyms; a preface; a prologue; two appendices, on “ISO Standards for the OSI Model” and “DNA Phase V Architectural Specifications”; a glossary; and an index.

Part 1 contains three chapters: “Network Architecture,” “The OSI Reference Model,” and “The Digital Network Architecture.” The first deals with the need for a network architecture and with the standards organizations whose definitions permit open interconnection. The second summarizes the OSI reference model. This chapter should be required reading for those familiar only with proprietary networks. The third chapter of Part 1 introduces DNA, discusses the relationships among phases 1 through 5, and describes the recent integration of OSI model features into DNA on a layer-by-layer basis: essentially, DNA will support the Phase 4 upper layers on an OSI base as well as supporting an OSI application stack.

Part 2 describes DNA functional layers in eight chapters: “The Physical Layer,” “The Data Link Layer,” “The Network Layer,” “Network Layer Protocols,” “Network Layer Routing,” “The Transport Layer,” “The DNA Phase V Session Control Layer,” and “OSI Upper Layer Architecture.” Part 3, “Network Applications,” contains two short chapters: “DNA Applications” and “OSI Applications.”

Part 4, “Related Architectures and Mechanisms,” contains four chapters: “Distributed Computing Services,” “The Naming Service,” “Network Management,” and “X.25 Access.” Subjects from the first two chapters are of likely interest to those interested in the Open Software Foundation’s distributed computing environment. Part 5, “Data Link Layer Protocols,” contains six chapters: “HDLC, SLDC, and LAPB Data Links,” “DDCMP Data Links,” “Local Area Network Data Links,” “CSMA/CD and Ethernet,” “Fiber Distributed Data Interface,” and “Bridge and Extended LAN  Architecture.” 

Throughout the book, material is organized in four parts: “the main text”; sections that contain the “thoughts of network architects,” who remain unidentified; boxes that contain supplementary information; and an excellent collection of diagrams that clarify or highlight the text. Unfortunately, the diagrams, boxes, and architects’ notes are neither indexed nor tabulated. This makes them difficult to use as a reference.

If you need to know more about DECnet and have an OSI background, or you need to know more about OSI communications and have a DECnet background, this book may prove helpful to you. If, on the other hand, you need to know more about OSI communications but do not have a DECnet background, proceed directly to one of the other excellent texts that have recently become available.