In order to fully appreciate the evolution of an enterprise data network one must first understand two historic developments of the modem (modulator and demodulator) and the first store and forward message switching (S/F MS) system. A modem allowed the emergence of 2-node networks for remote telemetry and computer-time sharing. Collins Radio Company that developed the first commercial modem in 1955 could not build these modems fast enough to satisfy the need. Mr. Melvin L.Doelz was awarded the original patent for the modem employing differentially coherent phase-shift-keying (DCPSK). Accordingly, a synchronous pulse train was created with each modulated pulse possessing a phase shift relative to the previous pulse determining information to be sent. Another unique feature of the modem was the use of multiple tones (each tone placed at null points) to send encoded information. Such a feature enabled the Collins modem to achieve a high data rate of 2400/4800 bps instead of the previous 300 bps.

The next big revolution in the area of communication networks dealt with the development of the first fully-automated (or SPC) commercial Store & Forward Message Switching (S/F MS) System under the guidance of Melvin L. Doelz. This system replaced the ubiquitous torn-tape teletype systems. The new computer-controlled S/F MS system revolutionized enterprise communication. Each S/F MS system required the segmentation of each incoming variable length message into small segments linked to one another via a short header imbedded into each fixed-length segment/packet, each to be stored in random access storage, disk storage and tape storage. For this reason, a S/F MS subsumes all the future packet switching systems. Again Mevin L. Doelz was awarded most of the critical patents related to this invention. All the banks, railroads, airlines, banks and similar geographically-distributed organizations wanted such a system. 

A need to design an economical enterprise data network arose immediately after a S/F MS became available in 1960. Almost all airlines, banks and railroads wanted a corporate MS system but didn't like the large monthly expense associated with leased transmission facilities. At that time, only two algorithms were available for designing a Minimal Spanning Tree (MST). One was published by Kruskal during 1956 and the other was developed by Prim of Bell Labs during 1957. But since both algorithms assumed links with no capacity constraints (i.e. no limitations on link bandwidth/data rates) their algorithms had to be extended for designing corporate data networks consisting of only 2400 or 4800 baud analog leased lines. That need gave birth to several algorithms for designing economical networks (or simply EcoNets).

Several individuals, prominently, Esau and Williams of IBM and Sharma of Collins Radio Company started developing algorithms for designing data communication networks consisting of several network links (or netlinks), each connecting several data terminals according to a topology called MultiPoint (MP) or MultiDrop(MD). Esau and Williams published their findings in 1966. Their algorithm is very popular among all the consultants. Sharma published a paper describing his algorithms in 1970 and a U.S. Patent was awarded on November 14, 1972 for his most efficient algorithm. Such an algorithm is really a combination of three separate algorithms, a new algorithm for synthesizing directed links (DLs) with capacity constraints, a new Exchange algorithm and Prim's MST algorithm. Sharma published a paper in 1983 comparing his most efficient algorithm with that of Esau and Williams and showed that it outperforms the Esau and Williams algorithm in most cases. During the four year period, 1970 -1974, other researchers, notably Frank, Frisch, Kershenbaum, Karnaugh and Chou also made significant contributions to this fascinating field.

The Shortest Forward Path and Shortest Backward Path algorithms that are employed in modern data communication networks are variations of the MST topologies as discussed above. Data networks for PCS backbones employ MD and star topologies. Most broadband and multimedia networks employ multi-level star topologies. Modern data LANs generally employ Open Bus (or Ethernet), Token Ring or multi-level star topologies. Modern MANs generally employ multi-level star topologies. One requires a very interactive tool to model all feasible topologies in a rapid fashion to select the most cost effective one. Please refer to Sharma's previously published papers or his recently published Textbook for a more detailed study of data network design algorithms. For a recently published paper on Packet Switching, please go to PSVnD.  For a short history of network design for voice and integrated voice, data and video applications please go to: A Short History of Enterprise Voice Network Design.