What You Will Learn

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What You Will Learn
After reading this chapter, you should be able to


Understand the IP version 4 (IPv4) addressing protocol, and the similarities to the addresses used in the postal delivery system Explain why hosts need two addresses, Ethernet and Internet, and how the Address Resolution Protocol (ARP) is used to determine the Ethernet address of a host given the host’s IP address Understand the TCP and UDP protocols, and how they are used to deliver data to a destination host Explain the TCP/IP layered model by comparing it to the layer model that was developed for the postal delivery system Differentiate between classful and classless IP addresses Learn how to subnet and summarize IP networks ✔







✔ ✔

Learn how routers forward packets using the longest match operation ✔

Describe the IP version 6 (IPv6) addressing protocol

CHAPTER 3

Internet Addressing and Routing
In Chapter 1, you examined systems for delivering the mail, planning a road trip, and making telephone calls. Chapter 2 introduced the binary, octal, and hexadecimal numbering systems. You need to understand how computers represent information, and how you can move between number systems to represent binary numbers in a more readable form. In this chapter, the concepts from the first two chapters will be combined to understand the schemes that are necessary to create a scalable computer communication system — the Internet.

Internet Addressing
To begin our discussion on computer communication over a network, this section looks at the similarities between mail delivery between houses, and data delivery between computers. The endpoints in mail delivery are houses, and the endpoints between electronic data delivery are computers. Certainly there can be other endpoints in both systems. Letters can be delivered from a house to a business, from a business to a house, between two businesses, and so on. Electronic data delivery can be from a news service to your cell phone or personal data assistant (PDA), from your computer to your friend’s pager, from environmental sensors in a building to the heating and cooling control systems for that building, and so on. But to keep the discussion simple, it will suffice to concentrate on mail delivery between houses, and electronic data delivery between computers. The first analogy is that an endpoint in a mail delivery system, a house, is equivalent to the endpoint in a computer communication system, a PC. (See Figure 3-1.)

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Chapter 3: Internet Addressing and Routing

Figure 3-1

Equivalent Endpoints in the Mail and Data Communication Systems

House

House

Computer

Computer

In the mail delivery system, the function of the post office is to deliver mail to a particular house. In the computer communication system, the function of the Internet is to deliver data to a particular PC. Yet, in both systems, the endpoint is not the ultimate destination. For mail, the ultimate recipient is a person. For data, the ultimate recipient is an application such as an e-mail program, a web browser, an audio or video program, an instant messaging program, or any number of wonderful applications that exist today. (See Figure 3-2.) Figure 3-2 Final Destinations in the Postal and Electronic Data Delivery Systems Laura Elvis E-mail Web Browser Instant Messaging

Debbie

House

Computer

Mail

Data

Internet Addressing 65

Although the ultimate recipient is a person or a software application, the responsibility of the systems stops when the mail, or data, is delivered to the proper house, or computer. However, as part of the address, you still need the ultimate recipient; either a person or an application, even though this information is not used for delivery to an endpoint. The endpoint uses the name or application to enable delivery to the recipient. Because the two systems are analogous, it is instructive to revisit the format of an address in the mail delivery system and...
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