1.4 Evolution of computer networks

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The term network can mean many different things. It can imply an interconnection of railway tracks for the rail network; highways and streets for transportation networks; telephone lines and switching centers for the phone network; coaxial lines for the cable television network; fiber lines for cable communications networks; or the interconnection of service centers, businesses, and so on to form a network. All of these configurations refer to the means to tie together various resources so that they may operate as a group, realizing the benefits of numbers, sharing, and communications in such a group.

In computer systems terminology of a network is a combination of interconnected computing equipment and programs used for moving information (and computations) between points (nodes) in the network where it may be generated, processed, stored, or used in whatever manner is deemed appropriate. The interconnection may take on many forms, such as dedicated links, shared links, telephone lines, microwave links, and satellite links. Networks in this sense form a loose coalition of devices that share information. This was one of the first uses of a network, although it was not the last. Users found that the network could offer more than just information sharing; it could offer other services for remote job execution and ultimately distributed computing.

The earliest concept of a network was of a loose binding together of devices or resources for sharing. An early computer communications network that exhibited these traits was the ARPANET. ARPANET was first brought on-line in 1969 as a research tool to investigate long-haul network issues and to provide a tool for research and development solutions. It has evolved into the Internet, connecting millions of computers over local area networks, metropolitan area networks, and other wide area networks. ARPANET provided the vehicle for early research into communications protocols dealing with congestion, control, routing, addressing, remote invocation, distributed computing, distributed operating systems and services, and many other areas.

The reasons for using networks such as ARPANET were to provide greater availability and access to a wider range of devices. Early applications of computers dealt with performing engineering tasks and major data processing functions. As the technology of computers changed, and as researchers and users alike added more and more applications, information access and manipulation took on greater emphasis.

Earlier networks provided the necessary information exchange services but were limited to basically just this service. The information availability stimulated more imaginative uses of this information. As this occurred and the technology of networks improved, new applications arose. These new applications not only used information exchange but also remote job execution. It began simply as sending a batch job down the link to a less busy host, having the job completed there, and then shipping the results back to the originator.

This sufficed for awhile, but it still did not provide the real-time or interactive environments that users were beginning to become accustomed to, including more advanced protocols and network operating systems to provide further services for remote job invocation and synchronization. The era of the local area network was coming. The wide area networks' biggest shortfall was in throughput or turnaround time for jobs and interprocessor communications. Because of the wide distances, delays of seconds were commonplace and caused added overhead in performing otherwise simple tasks. Network designers saw the need to provide another link in the network: the local area network.

Local area networks began showing up on the networking landscape in the early to mid 1970s as mostly research activities in universities and government laboratories. It was not until Ethernet was released in the mid 1970s that LANs became more widely available. Since that time, numerous LAN designs have been produced to fit an extremely wide spectrum of user requirements-for example, the fiber ring. Additionally, standards have evolved, providing basic LAN topologies and their services to a greater number of users.

Local area networks are finding their way into all aspects of modern society. We find them in our homes through cable modems and phone modems, automobiles via wireless technologies, banking (e.g., ATMs), schools via Internet connections, businesses, government, and industry. There are not too many aspects of information exchange and data processing in which a LAN cannot be found. Local area networks and their associated technologies represent one of the great growth areas of the 1990s and early 2000s. As more and more LANs become available, so will new products and uses for them. LANs are used to connect all personal computers in offices, classrooms, factory floors, retail establishments, and now even many homes. They are used in these environments to send memoranda, issue directives, schedule meetings, transmit documents, send e-mail, discover new information, and process large volumes of data concurrently at many sites.

LANs are used to link factory robots together with area and factory controllers. They provide sensor data, control data, and feedback to the control centers, while at the same time providing a vehicle to issue production changes and notices to users and robots alike. A fine example of a local area network providing diverse services to the users is seen in Walt Disney World. Disney uses LANs and computers to monitor all aspects of services, including fire protection, scheduling, ride management, on-line information, security, personnel services, and a plethora of other park management functions. Large banks, such as the World Bank, have adopted LANs as the means to interconnect their various local sites into smaller networks linked together by wide area networks. However, the LAN is not for everyone.

Network evolution has not stopped there. As wireless technology has improved, so has the interest in networking vendors to provide their services to users of these domains. Wireless networks began fairly quietly in the 1970s with the Aloha net as the foundation. Since then, wireless phone network development has opened the door for computer networks. Today one of the great growth areas in networking will be in further developing wireless networks and integrating these into existing LAN and WAN networks to provide an even wider array of applications to the wireless cell phone community.

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