Chapter 7

Introduction to TCP/IP

The following CompTIA A+ 220-801 Exam objectives are covered in this chapter:

• 2.3 Explain properties and characteristics of TCP/IP.
  • IP class
  • Class A
  • Class B
  • Class C
  • IPv4 vs. IPv6
  • Public vs. private vs. APIPA
  • Static vs. dynamic
  • Client-side DNS
  • DHCP
  • Subnet mask
  • Gateway
• 2.4 Explain common TCP and UDP ports, protocols, and their purpose.
  • Ports
  • 21 - FTP
  • 23 - Telnet
  • 25 - SMTP
  • 53 - DNS
  • 80 - HTTP
  • 110 - POP3
  • 143 - IMAP
  • 443 - HTTPS
  • 3389 - RDP
  • Protocols
  • DHCP
  • DNS
  • LDAP
  • SNMP
  • SMB
  • SSH
  • SFTP
  • TCP vs. UDP

Networking protocols are a lot like human languages in that they are the language that computers speak when talking to each other. If computers don’t speak the same language, they won’t be able to talk. To complicate matters, there are dozens of different languages out there that computers can use. Just like humans, computers can understand and use multiple languages. Imagine you are on the street and someone comes up to you and speaks in Spanish. If you know Spanish, you will likely reply in kind. It doesn’t matter if both of you know English as well because you’ve already established that you can communicate. On the other hand, it’s going to be a pretty quick conversation if you don’t know Spanish. This same concept applies to computers that are trying to communicate. They must have a network protocol in common in order for the conversation to be successful.

Throughout the years, hundreds of network protocols have been developed. As the advent of networking exploded, various companies developed their own networking hardware, software, and proprietary protocols. Some were incorporated as an integral part of the network operating system, such as Banyan VINES. One-time networking giant Novell had IPX/SPX. Microsoft developed NetBEUI. Apple created AppleTalk. Others included DECnet, SNA, and XNS. While a few achieved long-term success, most have faded into oblivion. The one protocol suite that has sustained is TCP/IP. While it has some structural plusses such as its modularity, it didn’t necessarily succeed because it was inherently superior to other protocols. It succeeded because it is the protocol of the Internet.

This chapter focuses on the TCP/IP protocol. It is the protocol used on the Internet, but it’s also the protocol used by the vast majority of home and business networks today. We’ll start by taking a quick look at the history of TCP/IP and the model on which it’s based. Then, we’ll dive deeper into TCP/IP structure and the individual protocols that compose it. From there, we’ll spend some time on IP addressing, including IPv4 and IPv6. Entire books have been written on TCP/IP—there’s no way we could cover it entirely in one chapter. Instead, we’ll give you the foundation you need to understand it well and work effectively with it in the field.