01Chapter01 - CHAPTER 1 Introduction In this chapter, we...

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1 CHAPTER 1 Introduction In this chapter, we introduce the idea of networks and, in particular, local area net- works. We define a LAN and briefly discuss some LAN applications and LAN compo- nents. 1.1 NETWORKS A network is a set of devices (often referred to as nodes) connected by media links. A node can be a computer, printer, or any other device capable of sending and/or receiv- ing data generated by other nodes on the network. The links connecting the devices are often called communication channels. Today when we speak of networks, we are generally referring to three primary cat- egories: local area networks (LANs), metropolitan area networks (MANs), and wide area networks (WANs). The category a network falls into is determined by its size, its ownership, the distance it covers, and its physical architecture (see Figure 1.1). Figure 1.1 Categories of networks Metropolitan area network (MAN) Local area network (LAN) Network Wide area network (WAN)
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2 CHAPTER 1 INTRODUCTION Local Area Network A local area network (LAN) is usually privately owned and links the devices in a sin- gle office, building, or campus (see Figure 1.2). Depending on the needs of an organi- zation and the type of technology used, a LAN can be as simple as two PCs and a printer in someone’s home office, or it can extend throughout a company and include voice, sound, and video peripherals. Currently, LAN size is limited to a few kilometers. LANs are designed to allow resources to be shared between personal computers or workstations. The resources to be shared can include hardware (e.g., a printer), soft- ware (e.g., an application program), or data. A common example of a LAN, found in many business environments, links a work group of task-related computers, for exam- ple, engineering workstations or accounting PCs. One of the computers may be given a large-capacity disk drive and become a server to the other clients. Software can be stored on this central server and used as needed by the whole group. In this example, the size of the LAN may be determined by licensing restrictions on the number of users per copy of software, or by restrictions on the number of users licensed to access the operating system. In addition to size, LANs are distinguished from other types of networks by their transmission media and topology. In general, a given LAN will use only one type of transmission medium. Traditionally, LANs have data rates in the 4 to 16 Mbps range. Today, however, it is very common for LANs to have data rates of 100 Mbps or 1 Gbps. Metropolitan Area Network A metropolitan area network (MAN) is designed to extend over an entire city. It may be a single network such as a cable television network, or it may be a means of connecting Figure 1.2 LAN b. Multiple-building LAN a. Si
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SECTION 1.1 NETWORKS 3 a number of LANs into a larger network so that resources may be shared LAN-to-LAN as well as device-to-device. For example, a company can use a MAN to connect the LANs in all of its offices throughout a city (see Figure 1.3).
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01Chapter01 - CHAPTER 1 Introduction In this chapter, we...

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