Leasing a (Network) Roadway Between Two Points

Chapter 14. Leasing a (Network) Roadway Between Two Points

What You Will Learn

After reading this chapter, you should be able to

• List several similarities and differences between using an Ethernet cross-over cable or a WAN link between two routers

• List two reasons why using a telephone company for WAN services makes sense

• Explain the meaning behind basic telephone company jargon used with WAN links

• Explain IP routing over point-to-point WAN links

• Describe the HDLC and PPP encapsulation processes

Throughout this book, you've seen many analogies to driving, roads, and the like, both in the text and in the titles. This part of the book makes a few analogies with roads, but the upcoming chapters will also make other analogies with things you already knowat least if you've read the chapters in sequence! In the next few chapters, you'll compare new networking topics to other networking topics, particularly Ethernet. Novel concept, huh?

Wide-area networks (WANs) refer to physical network connections that typically run between sites that are far apart. Local-area networks (LANs) are also physical networks, but they typically connect devices that are relatively close together.

As it turns out, WANs and LANs have another differencea difference that matters a lot to basic understanding of how each is built. With LANs, you are in control. You can buy cable, run it, connect it to the switches, plug in things where you want them in the switch, and it works. With WANs, you can't just run a cable. Even if the WAN link is a mile long, you typically can't run a cable over the streets to your other building. It's typically illegal, even if you could run the cable under the street where hopefully no one would mess with it.