interface for network services on Windows computers. It’s installed automatically when you install TCP/IP, but doesn’t show up as a separate protocol when you view the network connection properties (refer to Figure 1-1). NetBIOS is a session layer protocol that can work with transport layer protocols, such as TCP, SPX, or NetBEUI.
Network BIOS Extended User Interface (NetBEUI): A transport layer protocol designed for early IBM and Microsoft networks. NetBEUI is now considered obsolete.
IPX/SPX: A protocol suite made popular in the 1980s by Novell for use with its NetWare servers. TCP/IP has become so dominant that IPX/SPX is rarely used now.
AppleTalk: An obsolete suite of network protocols introduced by Apple in the 1980s and finally abandoned in 2009. The AppleTalk suite included a physical and data link layer protocol called LocalTalk, but could also work with standard lower-level protocols, including Ethernet and token ring.
Systems Network Architecture (SNA): An IBM networking architecture dating back to the 1970s, when mainframe computers roamed the earth and PCs had barely emerged from the primordial computer soup. SNA was designed primarily to support huge terminals such as airline reservations and banking systems, with tens of thousands of terminals attached to central host computers. Now that IBM mainframes that support TCP/IP and mainframe terminal systems have all but vanished, SNA is beginning to fade away. Still, many networks that incorporate mainframe computers have to contend with SNA.
Chapter 2
TCP/IP and the Internet
IN THIS CHAPTER
Many years ago, Transmission Control Protocol/Internet Protocol (TCP/IP) was known primarily as the protocol of the Internet. The biggest challenge of getting a local area network (LAN) connected to the Internet was figuring out how to mesh TCP/IP with the proprietary protocols that were the basis of the LANs — most notably Internetwork Packet Exchange/Sequenced Packet Exchange (IPX/SPX) used by Novel networks and NetBIOS Extended User Interface (NetBEUI) used by Microsoft networks.
Eventually, both IPX/SPX and NetBIO gave way to TCP/IP as the basis for local area networking, eliminating the challenge of translating IPX/SPX or NetBEUI to TCP/IP. As a result, TCP/IP is not just the protocol of the Internet now, but it’s also the protocol on which most LANs are based.
This chapter is a gentle introduction to the Internet in general and the TCP/IP suite of protocols in particular. After I get the introductions out of the way, you’ll be able to focus more in-depth on the detailed TCP/IP information given in the remaining chapters of Book 2.
What Is the Internet?
The Goliath of all computer networks, the Internet links hundreds of millions of computer users throughout the world. Strictly speaking, the Internet is a network of networks. It consists of hundreds of thousands of separate computer networks, all interlinked, so that a user on any of those networks can reach out and potentially touch a user on any of the other networks. This network of networks connects more than a billion computers to each other. (That’s right, billion with a b.)
One of the official documents (RFC 2026) of the Internet Engineering Task Force (IETF) defines the Internet as “a loosely organized international collaboration of autonomous, interconnected networks.” Broken down piece by piece, this definition encompasses several key aspects of what the Internet is:
Loosely organized: No single organization has authority over the Internet. As a result, the Internet is not highly organized. Online services, such as America Online or MSN, are owned and operated by individual companies that control exactly what content appears on the service and what software can be used with the service. No one exercises that kind of control over the Internet. As a result, you can find just about any kind of material imaginable on the Internet. No one guarantees the accuracy of information that you find on the Internet, so you have to be careful as you work your way through the labyrinth.
International: Nearly 200 countries are represented on the Internet, from Afghanistan to Zimbabwe. JUST HOW BIG IS THE INTERNET?Because the Internet is not owned or controlled by any one organization, no one knows how big the Internet really is. Several organizations do attempt to periodically determine the size of the Internet, including the Internet Systems Consortium (ISC), which completed its last survey in January 2019 and found that well over a billion host computers are connected to the Internet. The first year the ISC did the survey (1993), it found only 1.3 million host computers. It passed 10 million hosts in 1996, 100 million hosts in 2000, and edged over 1 billion hosts in 2014.Unfortunately, no one knows how many actual users are on the Internet. Each host can support a single user — or in the case of domains, hundreds of thousands or perhaps even millions of users. No one really knows.In fact, the ISC gave up on trying to count the number of hosts on the Internet. The January 2019 survey was its last. If you’re interested, you can check its historical survey data at www.isc.org/network/survey.
Collaboration: The Internet exists only because many different organizations cooperate to provide the services and support needed to sustain it. For example, much of the software that drives the Internet is open source software that’s developed collaboratively by programmers throughout the world, who constantly work to improve the code.
Autonomous: The Internet community respects that organizations that join the Internet are free to make their own decisions about how they configure and operate their networks. Although legal issues sometimes boil up, for the most part, each player on the Internet operates independently.
Interconnected: The whole key to the Internet is the concept of interconnection, which uses standard protocols that enable networks to communicate with each other. Without the interconnection provided by the TCP/IP protocol, the Internet would not exist.
Networks: The Internet would be completely unmanageable if it consisted of half a billion individual users, all interconnected. That’s why the Internet is often described as a network of networks. Most individual users on the Internet don’t access the Internet directly. Instead, they access the Internet indirectly through another network, which may be a LAN in a business or academic environment, or a dialup or broadband network provided by an Internet service provider (ISP). In each case, however, the users of the local network access the Internet via a gateway IP router.The Internet is composed of several distinct types of networks: Government agencies, such as the Library of Congress and the White House; military sites (did you ever see War Games or any of the Terminator movies?); educational institutions, such as universities and colleges (and their libraries); businesses, such as Microsoft and IBM; ISPs, which allow individuals to access the Internet; and commercial online services, such as America Online and MSN.
