Chapter 1 begins with a discussion of the basic components of telephone and computer networks, and their interaction. This chapter continues with the introduction of the centralized and distributive processing networks, and outlines the differences among these networks. It concludes with a discussion of Local Area Networks (LANs), Metropolitan Area Networks (MANs), and Wide Area Networks (WANs). Chapter 2 begins with a discussion on protocols to establish their relevance to the International Standards Organization (OSI) Management Model. Protocols are covered in more detail on Chapter 3. This chapter introduces several network devices and identify those that operate at different layers of the OSI model. It concludes with a discussion of the IEEE 802 Standards. Chapter 3 introduces several protocols including X.25, TCP/IP, IPX/SPX, NetBEUI, AppleTalk, and DNA. In this chapter, we learn how these protocols combine to form a suite of protocols that work at the various layers of the OSI model. Chapter 4 presents the various physical network connections. It begins with the different physical topologies, bus, star, ring, and mesh. Then, it introduces the network types including the ARCNet, Ethernet, Token Ring, and Fiber Distributed Data Interface (FDDI). A discussion of the wiring types and methods used in each of these network types is also included. Chapter 5 begins with a discussion of the different buses, past and present. Network adapters are discussed next. The chapter concludes with the introduction of the different components that work together to provide source-to-destination data transmissions between devices on the same network or different networks. Discussions on Bluetooth and Wi-Fi are also included. Chapter 6 focuses on wired and wireless transmissions. No previous knowledge of data communications is required for understanding the topics of this chapter. Chapter 7 is devoted to discussions on the various types of networks that we can use for our needs, the hardware and software required, and tasks that a network administrator must perform to maintain the network(s) he is responsible for. These tasks include security and safeguarding data from internal and external disasters. Chapters 8 and 9 are introductions to SNMP and RMON respectively. This text contains five appendices, A through E. Appendix A is a brief introduction to network analysis as defined in operations research which is a branch of mathematics concerned with financial and engineering economic problems. A simple and yet practical example is included. Appendix B contains a review of the binary information representation, and the standard codes used for information processing systems, communications systems, and associated equipment. It provides the basic concepts to illustrate how networking devices work and communicate with others. Appendix C is a review of the decimal, binary, octal, and hexadecimal numbers, their representation, and conversion from one base to another. The conversion procedures are illustrated with several examples. Appendix D serves as a supplement to Chapter 8. It presents the Local, ciscoMgmt, and Temporary variables of the Management Information Base (MIB) for Cisco Internetwork Operating System (IOS) Release 11.2. Finally, Appendix E is a glossary of terms and acronyms that are used in networks and on the Internet.