On Distributed Communications Series

XI. Summary Overview

I. Introduction

The introductory Memorandum in the series On Distributed Communications described a set of basic concepts, the details of which have been greatly expanded in the intervening Memoranda in the series. The series as a whole is an examination of the feasibility of any digital communications system utilizing "hot-potato routing" and automatic error detection. While preparing the draft of this concluding number, it became evident that a distinct and specific system was being described, which we have now chosen to call the "Distributed Adaptive Message Block Network," in order to distinguish it from the growing set of other distributed networks and systems, as described in ODC-V.[1]

The Goal

An ideal electrical communications system can be defined as one that permits any person or machine to reliably and instantaneously communicate with any combination of other people or machines, anywhere, anytime, and at zero cost.

It should effectively allow the illusion that those in communication with one another are all within the same soundproofed room--and that the door is locked.

Almost by definition, all electrical communications systems will fall short of meeting these goals, the shortcomings we are content to live with being determined on the basis of intended application and price. Presentday networks are designed to do one particular set of tasks well. In the future, we shall make even greater demands upon our networks and shall consider new ways of building communications networks taking advantage of the newly emerging computer-based technology.


Let us consider one way we might go about building a new system to meet the requirements of the future. We shall attempt to start from scratch and ignore the traditional approach of existing communications systems. We shall first focus upon those requirements--particularly military--not being fully satisfied by today's systems.

For example, in their outstanding study of Army communications, Bloom, Mayfield, and Williams, of the Franklin Institute,[2] conducted a survey among Army Officers on shortcomings of present-day Army communications. Their findings are shown in Fig. 1.

Fig. 1--Principal Problems in Army Communications[3]

We have used the Bloom, Mayfield, and Williams data as a check list against which the distributed network has been evaluated. The separate mechanisms included within the distributed system to match these "problems" are presented in Table I.

This list wasn't available at the time the system synthesis was initiated, and we chose a somewhat different, but similar, set of criteria. (Survivability was placed at the top of our list.)

The aim was towards an "ideal" electrical communication system. But a real-life system is a collection of compromises, and this system is no exception. The author believes, though, that it represents an acceptable price to have to pay for a national communications system able to meet the extreme demands of survivability in the face of a determined enemy. Some of the system's disadvantages and advantages are summarized in the next sections, together with references to the volumes in the series in which the particular topic is detailed.

[1] ODC is an abbreviation of the series title, On Distributed Communications; the number following refers to the particular volume within the series. A list of all items in the series is found on p. 21.

[2] Bloom, Joel N., Clifton E. Mayfield, and Richard M. Williams, People, Organizations, and Communications, Final Report, F-A312. Prepared for Army Communications Systems Division by the Franklin Institute Laboratories for Research and Development, Philadelphia, January 1962.

[3] From: Bloom, et al., ibid, p. 30.

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