Overview

In this chapter we focus our attention on Ethernet. In previous chapters, we informally mentioned Ethernet in order to illustrate various network concepts. For example, at the data link layer Ethernet was used as an example to demonstrate frame formats, MAC hardware addresses, and network switches. In this chapter the subject of Ethernet is presented in a more formal and comprehensive manner, including its history and its latest evolution, Gigabit Ethernet.

1. What exactly is Ethernet and what is its origin?

   Ethernet is a local area network protocol developed jointly by Xerox, Intel, and Digital Equipment Corporation (DEC) at the Xerox Palo Alto Research Center (PARC) in the mid-1970s. It was designed as a technology that would allow for the interconnection of office devices. Although the concept of Ethernet was originally developed at PARC, Ethernet's genesis is with Norman Abramson of the University of Hawaii in the late 1960s to early 1970s. Abramson developed a network called ALOHA, which was used to connect the main campus site in Oahu to seven other campuses on four of the Hawaiian islands. Using a technique called contention, Abramson demonstrated that multiple nodes on a network could use the same channel for communications and they could send data whenever they had data to send. The primary difference between the ALOHA network and Ethernet is that ALOHA permitted any node to transmit data at any time, made no provision to allow a node to detect if another node was sending data, and there...