14.1 INTRODUCTION

This chapter examines local area networks (LANs), which interconnect multiple communicating devices within a limited geographic area, typically within a single building or site. Historically, networks interconnecting several LANs within a city or campus were termed metropolitan area networks (MANs), while wide area networks (WANs) extended connectivity over regional, national, or global distances, linking multiple LANs or MANs through public or private telecommunications infrastructure.

Although LANs, MANs, and WANs were originally based on distinct physical media and protocol technologies, the boundaries between them have become increasingly blurred. High-speed optical links, virtual private networks, and Internet-based services now enable seamless communication between devices regardless of physical separation or transmission medium or, in modern networking, regardless of the degree of mobility.

It is therefore conceptually more useful to distinguish between networking—the interconnection of devices within a local domain—and internetworking—the interconnection of networks through routing and transport-layer protocols. Networking is addressed in this chapter; internetworking is the subject of the next.

The evolution of networking has brought a range of important benefits, including:

the interconnection of users and devices into collaborative workgroups;
the sharing of costly resources, such as printers, storage, and processing power;
corporate-wide and global access to data and information systems; and
the integration of information (data) with processes and applications across an organization.

The following sections describe the key concepts and standards underpinning modern networking, including layered reference models, the IEEE 802 family of networking standards, common LAN topologies, transmission media, media-access control techniques, and network devices. We investigate internetworking in Chapter 15.