Network Protocols

In Chapters 1 through 3 we mainly concentrated on Physical and Data Link layer technologies, protocols, and specifications. These characteristics of LANs (and WANs) are absolutely essential to understand. However, as we move closer to the world of routers and routing, we have to start looking at the protocols that ride on top of these technologies. While a variety of network protocols exist for the purpose of moving data across an internetwork, three in particular make up the bulk of the implementations that you’ll come across. These include TCP/IP, IPX/SPX, and AppleTalk.

The first important thing to understand is that none of these protocols define a single entity. Instead, each represents what is known as a protocol suite. A protocol suite is actually a group of protocols that work together (at different layers) to make network communication possible. If you recall from Chapter 1, most network protocol suites do not map to the OSI model directly, but include protocols that can generally be mapped to defined OSI layers. Some suites (such as AppleTalk) map to the OSI model more clearly than others. In this chapter we’ll not only look at the protocols that make up the TCP/IP, IPX/SPX, and AppleTalk suites, but also relate these protocols to the layers of the OSI model.

The material to be covered in this chapter includes:

  • Transmission Control Protocol / Internet Protocol (TCP/IP)
  • Internetwork Packet Exchange / Sequenced Packet Exchange (IPX/SPX)

Author: Dan DiNicolo

Dan DiNicolo is a freelance author, consultant, trainer, and the managing editor of He is the author of the CCNA Study Guide found on this site, as well as many books including the PC Magazine titles Windows XP Security Solutions and Windows Vista Security Solutions. Click here to contact Dan.