Ethernet: The Definitive Guide

Chapter 6. Ethernet Media Fundamentals

To send Ethernet signals from one station to another, stations are connected to one another with a media system based on a set of standard components. Some of these are hardware components specific to each media cabling system, such as the media cables and connectors. These media-specific components are described in the individual media chapters and cabling chapters that follow. Other components, such as Ethernet interfaces, are common to all media systems. Reading this chapter will provide the background you need to understand the components that connect to each of the Ethernet systems: 10-, 100-, or 1000 Mbps.

As the Ethernet system has evolved, it has developed a set of medium-independent attachments. Medium independence means that the Ethernet interface does not have to know anything about the media system. These attachments allow an Ethernet interface to be connected to any type of media system. With this system, multiple media systems can be developed without requiring any changes in the Ethernet interface controllers.

The first medium-independent attachment was developed for the 10 Mbps Ethernet system, and is called the attachment unit interface (AUI). The AUI supports the 10 Mbps media systems only. The next medium-independent attachment was developed as part of the Fast Ethernet standard, and is called the medium-independent interface (MII). The MII provides support for both 10 and 100 Mbps media segments. Finally, a gigabit medium-independent ...