This chapter introduces the media signaling components in the standard, and the Energy Efficient Ethernet extensions that modify the Ethernet signaling to save power when no data is being sent. Knowing how the media signaling components are organized and what they are called is helpful for understanding the ways Ethernet interfaces are connected to the various media systems and how they send signals over an Ethernet link.
To send Ethernet signals from one station to another, stations are connected over a cabling system based on a set of standard signaling components. Some of these are hardware components specific to each media cabling system. These media-specific components are described in more detail in the individual media chapters and cabling chapters that follow.
Other signaling components, such as Ethernet interface electronics, are common to all media systems. The standard refers to the specifications for these elements as “compatibility interfaces,” because they ensure that stations can communicate in a compatible manner. The common signaling elements are described in this chapter.
Figure 7-1 shows a logical diagram of Ethernet stations A and B, connected over a link, with the physical layer standards involved shown in gray. The physical layer standards include further sublayers that are shown in more detail in Figure 7-2. Each station implements the same set of physical layer standards.