Chapter 13. Ethernet: The Universal Standard

SOME OF THE MAIN TOPICS IN THIS CHAPTER ARE

A Short History of Ethernet 196

Collisions: What Are CSMA/CA and CSMA/CD? 199

Restrictions on Legacy Ethernet Topologies 203

Using a Bus Topology 204

Using a Star Topology 205

Hybrid LAN Topologies 206

Using a Backbone to Connect the Enterprise 208

Ethernet Frames 208

Fast Ethernet (IEEE 802.3u) and Gigabit Ethernet (IEEE 802.3z) 213

Ethernet Problems 217

Ethernet Errors 220

Monitoring Errors 223

If you sit down at almost any PC or desktop workstation today, it is very likely that the computer will be linked to the local network by one form of Ethernet or another. Although other local area networking (LAN) technologies, such as Token-Ring or Novell's proprietary IPX/SPX, are still around, Ethernet-connected computers outnumber all other LAN technologies combined. You'll also find that, most likely, Ethernet is the underlying networking technology that connects servers, printers, and other devices on your network. Ethernet has become so pervasive that every major manufacturer of networking equipment sells equipment that is designed to work with or provide interconnectivity with Ethernet LANs.

So before we start talking about network transport protocols, services, and applications, it is important that you get a good understanding of what Ethernet is and how it functions. It's also important that you understand that there is more than one type of Ethernet. What started out as a simple LAN technology has evolved to the point that it is now seriously considered a wide area networking (WAN) technology. With technologies such as PPPOE, (Point-to-Point Protocol over Ethernet) which is a method for building PPP sessions and encapsulating packets, as described in RFC 2516 (http://www.ietf.org/rfc/rfc2516.txt), network providers of all typesDSL-based ISPs, for exampleuse Ethernet to provide connectivity to their networks. From the first commercial versions that operated at 10Mbps to the newest 10Gigabit Ethernet, you'll find that there's an Ethernet solution to most network problems you encounter. It's on the desktop. It's in the wiring closet. It's the backbone of your network.

In this chapter, we'll first look at how Ethernet got its start, and then describe the different versions that were standardized and marketed. After giving you a thorough lesson in Ethernet technology, we'll look at techniques that can be used to troubleshoot Ethernet networks.