Overview

In the late 1970s, a major battle arose in the communications and the computer industries. Convergence of the two industries was happening as a result of the implementation of the Local Area Networks (LANs). In the local networking arena, users began to implement solutions to their data connectivity needs within a localized environment. Two major choices were available for their installation of wiring: baseband coaxial cable and broadband coaxial cable.

The baseband cable was based on the Ethernet developments using a 20 MHz, 50 W coax. Designed as a half-duplex operation, Ethernet allowed the end user to transmit digital data on the cable at speeds of up to 10 Mbps. Clearly, the 10 Mbps was maximum throughput, but was attractive in comparison to the technology of twisted pair at the time (telephone wires were capable of less than 1 Mbps bursty data). Moreover, the use of the baseband technology allowed the data to be digitally applied directly onto the cable system. No analog modulation was necessary to apply the data. It was dc input placed directly onto the cable. The signal propagates to both ends of the cable before another device can transmit. This is shown as a quick review in Figure 15-1. To control the cable access, the attached devices used Carrier Sense Multiple Access with Collision Detection (CSMA/CD) as the access control. CSMA/CD allowed for the possibility that two devices may attempt to transmit on the cable at the same time, causing a...