On Distributed Communications Series

Publications in the "On Distributed Communications" Series

An electrical engineer by training, Paul Baran worked for Hughes Aircraft Company's systems group before joining RAND in 1959. While working at RAND on a scheme for U.S. telecommunications infrastructure to survive a "first strike," Baran conceived of the Internet and digital packet switching, the Internet's underlying data communications technology. His concepts are still employed today; just the terms are different. His seminal work first appeared in a series of RAND studies published between 1960 and 1962 and then finally in the tome "On Distributed Communications," published in 1964.

Since the early 1970s as an entrepreneur and private investor, Baran has founded or co-founded several high-tech telecommunications firms. He is currently chairman and co-founder of Com21, Inc., a Silicon Valley-based manufacturer of cable TV modems for high-speed, high-bandwidth Internet access. He is also a co-founder of the Institute for the Future. Baran holds several patents and has received numerous professional honors including an honorary doctorate from his alma mater Drexel University (BS '49). He has a master's degree in engineering from UCLA.

The following documents in this series are presented in their entirety in HTML format.

I. Introduction to Distributed Communications Networks

Paul Baran, RM-3420-PR

Introduces the system concept and outlines the requirements for and design considerations of the distributed digital data communications network. Considers especially the use of redundancy as a means of withstanding heavy enemy attacks. A general understanding of the proposal may be obtained by reading this volume and Vol. XI.

II. Digital Simulation of Hot-Potato Routing in a Broadband Distributed Communications Network

Sharla P. Boehm and Paul Baran, RM-3103-PR

Describes a computer simulation of the message routing scheme proposed. The basic routing doctrine permitted a network to suffer a large number of breaks, then reconstitute itself by rapidly relearning to make best use of the surviving links.

III. Determination of Path-Lengths in a Distributed Network

J. W. Smith, RM-3578-PR

Continues model simulation reported in Vol. II. The program was rewritten in a more powerful computer language allowing examination of larger networks. Modification of the routing doctrine by intermittently reducing the input data rate of local traffic reduced to a low level the number of message blocks taking excessively long paths. The level was so low that a deterministic equation was required in lieu of Monte Carlo to examine the now rare event of a long message block path. The results of both the simulation and the equation agreed in the area of overlapping validity.

IV. Priority, Precedence, and Overload

Paul Baran, RM-3638-PR

The creation of dynamic or flexible priority and precedence structures within a communication system handling a mixture of traffic with different data rate, urgency, and importance levels is discussed. The goal chosen is optimum utilization of the communications resource within a seriously degraded and overloaded network.

V. History, Alternative Approaches, and Comparisons

Paul Baran, RM-3097-PR

A background paper acknowledging the efforts of people in many fields working toward the development of large communications systems where system reliability and survivability are mandatory. A consideration of terminology is designed to acquaint the reader with the diverse, sometimes conflicting, definitions used. The evolution of the distributed network is traced, and a number of earlier hardware proposals are outlined.

VI. Mini-Cost Microwave

Paul Baran, RM-3762-PR

The technical feasibility of constructing an extremely low-cost, all-digital, X- or Ku -band microwave relay system, operating at a multi-megabit per second data rate, is examined. The use of newly developed varactor multipliers permits the design of a miniature, all-solid-state microwave repeater powered by a thermoelectric converter burning L-P fuel.

VII. Tentative Engineering Specifications and Preliminary Design for a High-Data-Rate Distributed Network Switching Node

Paul Baran, RM-3763-PR

High-speed, or "hot-potato," store-and-forward message block relaying forms the heart of the proposed information transmission system. The Switching Nodes are the units in which the camplex processing takes place. The node is described in sufficient engineering detail to estimate the components required. Timing calculations, together with a projected implementation scheme, provide a strong toundation for the belief that the construction and use of the node is practical.

VIII. The Multiplexing Station

Paul Baran, RM-3764-PR

A description of the Multiplexing Stations which connect subscribers to the Switching Nodes. The presentation is in engineering detail, demonstrating how the network will simultaneously process traffic from up to 1024 separate users sending a mixture of start-stop teletypewriter, digital voice, and other synchronous signals at various rates.

IX. Security, Secrecy, and Tamper-Free Considerations

Paul Baran, RM-3765-PR

Considers the security aspects of a system of the type proposed, in which secrecy is of paramount importance. Describes the safeguards to be built into the network, and evaluates the premise that the existence of "spies" within the supposedly secure system must be anticipated. Security provisions are based on the belief that protection is best obtained by raising the "price" of espied information to a level which becomes excessive. The treatment of the subject is itself unclassified.

X. Cost Estimate

Paul Baran, RM-3766-PR

A detailed cost estimate for the entire proposed system, based on an arbitrary network configuration of 400 Switching Nodes, servicing 100,000 simultaneous users via 200 Multiplexing Stations. Assuming a usable life of ten years, all costs, including operating costs, are estimated at about $60,000,000 per year.

XI. Summary Overview

Paul Baran, RM-3767-PR

Summarizes the system proposal, highlighting the more important features. Considers the particular advantages of the distributed network, and conuents on disadvantages. An outline is given of the manner in which future research aimed at an actual implementation of the network might be conducted. Together with the introductory volume, it provides a general description of the entire system concept.