Content Overview Bandwidth is a crucial component in networking. Bandwidth decisions are among the most important when a network is designed. This module discusses the importance of bandwidth, explains how it is calculated, and how it is measured. Functions of networking are described using layered models. This module covers the two most important models, which are the Open System Interconnection (OSI) model and the Transmission Control Protocol/Internet Protocol (TCP/IP) model. The module also presents the differences and similarities between the two models. In addition, this module presents a brief history of networking. It also describes network devices, as well as cabling, physical, and logical layouts. This module also defines and compares LANs, MANs, WANs, SANs, and VPNs. Students completing this module should be able to:
Content 2.1 Networking Terminology 2.1.1 Data networks Data networks developed as a result of business applications that were written for microcomputers. At that time microcomputers were not connected as mainframe computer terminals were, so there was no efficient way of sharing data among multiple microcomputers. It became apparent that sharing data through the use of floppy disks was not an efficient or cost-effective manner in which to operate businesses. Sneakernet created multiple copies of the data. Each time a file was modified it would have to be shared again with all other people who needed that file. If two people modified the file and then tried to share it, one of the sets of changes would be lost. Businesses needed a solution that would successfully address the following three problems: Businesses realized that networking technology could increase productivity while saving money. Networks were added and expanded almost as rapidly as new network technologies and products were introduced. In the early 1980s networking saw a tremendous expansion, even though the early development of networking was disorganized. In the mid-1980s, the network technologies that had emerged had been created with a variety of different hardware and software implementations. Each company that created network hardware and software used its own company standards. These individual standards were developed because of competition with other companies. Consequently, many of the new network technologies were incompatible with each other. It became increasingly difficult for networks that used different specifications to communicate with each other. This often required the old network equipment to be removed to implement the new equipment. One early solution was the creation of local-area network (LAN) standards. Because LAN standards provided an open set of guidelines for creating network hardware and software, the equipment from different companies could then become compatible. This allowed for stability in LAN implementation. In a LAN system, each department of the company is a kind of electronic island. As the use of computers in businesses grew, it soon became obvious that even LANs were not sufficient. What was needed was a way for information to move efficiently and quickly, not only within a company, but also from one business to another. The solution was the creation of metropolitan-area networks (MANs) and wide-area networks (WANs). Because WANs could connect user networks over large geographic areas, it was possible for businesses to communicate with each other across great distances. Figure summarizes the relative sizes of LANs and WANs. Web Links IP-based Networks: Basics http://www.axis.com/documentation/ whitepaper/ip_networks_basics.htm
Content 2.1 Networking Terminology 2.1.2 Network history The history of computer networking is complex. It has involved many people from all over the world over the past 35 years. Presented here is a simplified view of how the Internet evolved. The processes of invention and commercialization are far more complicated, but it is helpful to look at the fundamental development. In the 1940s computers were large electromechanical devices that were prone to failure. In 1947 the invention of a semiconductor transistor opened up many possibilities for making smaller, more reliable computers. In the 1950s mainframe computers, which were run by punched card programs, began to be used by large institutions. In the late 1950s the integrated circuit that combined several, then many, and now millions, of transistors on one small piece of semiconductor was invented. Through the 1960s mainframes with terminals were commonplace, and integrated circuits were widely used. In the late 1960s and 1970s, smaller computers, called minicomputers came into existence. However, these minicomputers were still very large by modern standards. In 1977 the Apple Computer Company introduced the microcomputer, also known as the personal computer. In 1981 IBM introduced its first personal computer. The user-friendly Mac, the open-architecture IBM PC, and the further micro-miniaturization of integrated circuits led to widespread use of personal computers in homes and businesses. In the mid-1980s users with stand-alone computers started to share files using modems to connect to other computers. This was referred to as point-to-point, or dial-up communication. This concept was expanded by the use of computers that were the central point of communication in a dial-up connection. These computers were called bulletin boards. Users would connect to the bulletin boards, leave and pick up messages, as well as upload and download files. The drawback to this type of system was that there was very little direct communication and then only with those who knew about the bulletin board. Another limitation was that the bulletin board computer required one modem per connection. If five people connected simultaneously it would require five modems connected to five separate phone lines. As the number of people who wanted to use the system grew, the system was not able to handle the demand. For example, imagine if 500 people wanted to connect at the same time. Starting in the 1960s and continuing through the 70s, 80s, and 90s, the Department of Defense (DoD) developed large, reliable, wide-area networks (WANs) for military and scientific reasons. This technology was different from the point-to-point communication used in bulletin boards. It allowed multiple computers to be connected together using many different paths. The network itself would determine how to move data from one computer to another. Instead of only being able to communicate with one other computer at a time, many computers could be reached using the same connection. The DoDs WAN eventually became the Internet. Web Links Hobbes' Internet Timeline v6.0 http://www.zakon.org/robert/ internet/timeline/
Content 2.1 Networking Terminology 2.1.3 Networking devices Equipment that connects