ach. Explain the differences between a token-passing and a contention-based LAN. Why is Ethernet the preferred LAN scheme? What is the difference between 802.3 and Ethernet? What is the difference between a peer-to-peer network and a client-server network? Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. CHAPTER Access Technologies Access Technologies Chapter 6 For the longest time, "access" described the manner in which customers reached the network for the transport of voice services. In the last 20 years, however, that definition has changed dramatically. In 1981-20 years ago-IBM changed the world when it introduced the PC, and in 1984 the Macintosh arrived, bringing well-designed and organized com- puting power to the proverbial masses. Shortly thereafter, hobbyists began to take advantage of emergent modem technology and created online databases-the first bulletin board systems that allowed people to send simple text messages to each other. This accelerated the modem market dramatically, and before long data became a common component of local loop traffic. At that time there was no concept of instant messag- ing or of the degree to which e-mail would fundamentally change the way people communicate and do business. At the same time, the business world found more and more applications for data, and the need to move that data from place to place became a major contributor to the growth in data traffic on the world's telephone networks. In those heady, early days, data did not represent a problem for the bandwidth-limited local loop. The digital information created by a com- puter and intended for transmission through the telephone network was received by a modem, converted into a modulated analog waveform that fell within the 4 KHz voice band, and fed to the network without inci- dent. As we mentioned in an earlier chapter, the modem's job 